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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><strong><b><font size=5 color=navy face=Arial><span
style='font-size:18.0pt;font-family:Arial;color:navy'>“ </span></font></b></strong><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<h1><b><font size=6 color=red face="Times New Roman"><span style='font-size:
24.0pt;color:red'>Light Emitting Diodes (LEDs)</span></font><o:p></o:p></b></h1>
<p><font size=2 face="Times New Roman"><span style='font-size:10.0pt'><a
href="http://www.kpsec.freeuk.com/components/led.htm#colours">Colours</a> | <a
href="http://www.kpsec.freeuk.com/components/led.htm#sizes">Sizes and shapes</a>
| <a href="http://www.kpsec.freeuk.com/components/led.htm#calculate">Resistor
value</a> | <a href="http://www.kpsec.freeuk.com/components/led.htm#series">LEDs
in series</a> | <a href="http://www.kpsec.freeuk.com/components/led.htm#data">LED data</a> |
<a href="http://www.kpsec.freeuk.com/components/led.htm#flashing">Flashing</a> |
<a href="http://www.kpsec.freeuk.com/components/led.htm#displays">Displays</a></span></font>
<br clear=all>
<o:p></o:p></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>Example:
<img border=0 width=142 height=39 id="_x0000_i1025"
src="cid:image001.gif@01C93EAB.55172640" alt=LED align=middle>
Circuit symbol: <img border=0 width=182 height=49 id="_x0000_i1026"
src="cid:image002.gif@01C93EAB.55172640" alt="LED circuit symbol" align=middle>
<o:p></o:p></span></font></p>
<h3><b><font size=4 face="Times New Roman"><span style='font-size:13.5pt'>Function<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>LEDs emit light when an electric current passes through them. <o:p></o:p></span></font></p>
<h3><b><font size=4 face="Times New Roman"><span style='font-size:13.5pt'>Connecting
and soldering<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><!--[if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600"
o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f"
stroked="f">
<v:stroke joinstyle="miter" />
<v:formulas>
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<v:f eqn="sum @0 1 0" />
<v:f eqn="sum 0 0 @1" />
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<v:f eqn="prod @3 21600 pixelHeight" />
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<v:f eqn="prod @7 21600 pixelHeight" />
<v:f eqn="sum @10 21600 0" />
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<v:path o:extrusionok="f" gradientshapeok="t" o:connecttype="rect" />
<o:lock v:ext="edit" aspectratio="t" />
</v:shapetype><v:shape id="_x0000_s1026" type="#_x0000_t75" alt="LED connections"
style='position:absolute;margin-left:-15pt;margin-top:-240.75pt;width:84pt;
height:39.75pt;z-index:1;mso-wrap-distance-left:7.5pt;mso-wrap-distance-top:7.5pt;
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<v:imagedata src="cid:image003.gif@01C93EAB.55172640" o:title="ledak" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=112 height=53
src="cid:image003.gif@01C93EAB.55172640" align=left hspace=10 vspace=10
alt="LED connections" border=0 v:shapes="_x0000_s1026"><![endif]><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>LEDs must be connected
the correct way round, the diagram may be labelled <b><span style='font-weight:
bold'>a</span></b> or <b><span style='font-weight:bold'>+</span></b> for anode
and <b><span style='font-weight:bold'>k</span></b> or <b><span
style='font-weight:bold'>-</span></b> for cathode (yes, it really is k, not c,
for cathode!). The cathode is the short lead and there may be a slight flat on
the body of round LEDs. If you can see inside the LED the cathode is the larger
electrode (but this is not an official identification method). <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>LEDs can
be damaged by heat when soldering, but the risk is small unless you are very
slow. No special precautions are needed for soldering most LEDs. <br clear=all>
<o:p></o:p></span></font></p>
<h3><!--[if gte vml 1]><v:shape id="_x0000_s1027" type="#_x0000_t75" alt="Testing an LED"
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<v:imagedata src="cid:image004.gif@01C93EAB.55172640" o:title="ledtst" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=146 height=164
src="cid:image004.gif@01C93EAB.55172640" align=left hspace=10 vspace=10
alt="Testing an LED" border=0 v:shapes="_x0000_s1027"><![endif]><b><font
size=4 face="Times New Roman"><span style='font-size:13.5pt'>Testing an LED<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><font size=3 color=red face="Times New Roman"><span
style='font-size:12.0pt;color:red'>Never connect an LED directly to a battery
or power supply!</span></font> <br>
It will be destroyed almost instantly because too much current will pass
through and burn it out. <o:p></o:p></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>LEDs must
have a resistor in series to limit the current to a safe value, for quick
testing purposes a 1k<img border=0 width=12 height=11 id="_x0000_i1027"
src="cid:image005.gif@01C93EAB.55172640" alt=ohm> resistor is suitable for most
LEDs if your supply voltage is 12V or less. <b><span style='font-weight:bold'>Remember
to connect the LED the correct way round!</span></b> <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>For an
accurate value please see <a
href="http://www.kpsec.freeuk.com/components/led.htm#calculate">Calculating an
LED resistor value</a> below. <br clear=all>
<o:p></o:p></span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><a name=colours></a><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt'>Colours of LEDs<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><!--[if gte vml 1]><v:shape id="_x0000_s1028" type="#_x0000_t75"
alt="LED colours" style='position:absolute;margin-left:-15pt;margin-top:-57.75pt;
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<v:imagedata src="cid:image006.gif@01C93EAB.55172640" o:title="ledcol" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=294 height=142
src="cid:image006.gif@01C93EAB.55172640" align=left hspace=10 alt="LED colours"
border=0 v:shapes="_x0000_s1028"><![endif]><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>LEDs are available in red, orange, amber, yellow,
green, blue and white. Blue and white LEDs are much more expensive than the
other colours. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>The
colour of an LED is determined by the semiconductor material, not by the
colouring of the 'package' (the plastic body). LEDs of all colours are
available in uncoloured packages which may be diffused (milky) or clear (often
described as 'water clear'). The coloured packages are also available as
diffused (the standard type) or transparent. <br clear=all>
<o:p></o:p></span></font></p>
<h3><b><font size=4 face="Times New Roman"><span style='font-size:13.5pt'>Tri-colour
LEDs<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><!--[if gte vml 1]><v:shape id="_x0000_s1029" type="#_x0000_t75"
alt="Tri-colour LED" style='position:absolute;margin-left:-15pt;margin-top:-29.25pt;
width:58.5pt;height:146.25pt;z-index:4;mso-wrap-distance-left:7.5pt;
mso-wrap-distance-top:0;mso-wrap-distance-right:7.5pt;
mso-wrap-distance-bottom:0;mso-position-horizontal:absolute;
mso-position-horizontal-relative:text;mso-position-vertical:absolute;
mso-position-vertical-relative:line' o:allowoverlap="f">
<v:imagedata src="cid:image007.gif@01C93EAB.55172640" o:title="triled" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=78 height=195
src="cid:image007.gif@01C93EAB.55172640" align=left hspace=10
alt="Tri-colour LED" border=0 v:shapes="_x0000_s1029"><![endif]><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>The most popular type of
tri-colour LED has a red and a green LED combined in one package with three
leads. They are called tri-colour because mixed red and green light appears to
be yellow and this is produced when both the red and green LEDs are on. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>The
diagram shows the construction of a tri-colour LED. Note the different lengths
of the three leads. The centre lead (k) is the common cathode for both LEDs,
the outer leads (a1 and a2) are the anodes to the LEDs allowing each one to be
lit separately, or both together to give the third colour. <br clear=all>
<o:p></o:p></span></font></p>
<h3><b><font size=4 face="Times New Roman"><span style='font-size:13.5pt'>Bi-colour
LEDs<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>A bi-colour LED has two LEDs wired in 'inverse parallel' (one forwards,
one backwards) combined in one package with two leads. Only one of the LEDs can
be lit at one time and they are less useful than the tri-colour LEDs described
above. <o:p></o:p></span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><a name=sizes></a><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt'>Sizes, Shapes and Viewing angles of LEDs<o:p></o:p></span></font></b></h3>
<table class=MsoNormalTable border=0 cellpadding=0 align=right hspace=10>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center;mso-element:frame'><font
size=3 face="Times New Roman"><span style='font-size:12.0pt'><img border=0
width=122 height=95 id="_x0000_i1030" src="cid:image008.jpg@01C93EAB.55172640"
alt="LED Clip, photograph © Rapid Electronics"><o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center;mso-element:frame'><font
size=3 face="Times New Roman"><span style='font-size:12.0pt'>LED Clip<o:p></o:p></span></font></p>
<p align=center style='text-align:center;mso-element:frame'><font size=2
face="Times New Roman"><span style='font-size:10.0pt'>Photograph © <a
href="http://www.rapidonline.com/" target="_blank">Rapid Electronics</a></span></font><o:p></o:p></p>
</td>
</tr>
</table>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>LEDs are available in a wide variety of sizes and shapes. The
'standard' LED has a round cross-section of 5mm diameter and this is probably
the best type for general use, but 3mm round LEDs are also popular. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>Round
cross-section LEDs are frequently used and they are very easy to install on
boxes by drilling a hole of the LED diameter, adding a spot of glue will help
to hold the LED if necessary. LED clips are also available to secure LEDs in
holes. Other cross-section shapes include square, rectangular and triangular. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>As well as
a variety of colours, sizes and shapes, LEDs also vary in their viewing angle.
This tells you how much the beam of light spreads out. Standard LEDs have a
viewing angle of 60° but others have a narrow beam of 30° or less. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'><a
href="http://www.rapidonline.com/" target="_blank">Rapid Electronics</a> stock
a wide selection of LEDs and their catalogue is a good guide to the range
available. <br clear=all>
<o:p></o:p></span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><a name=calculate></a><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt'>Calculating an LED resistor value<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><!--[if gte vml 1]><v:shape id="_x0000_s1030" type="#_x0000_t75"
alt="LED resistor circuit" style='position:absolute;margin-left:-15pt;
margin-top:-108pt;width:156pt;height:123pt;z-index:5;mso-wrap-distance-left:7.5pt;
mso-wrap-distance-top:7.5pt;mso-wrap-distance-right:7.5pt;
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mso-position-vertical-relative:line' o:allowoverlap="f">
<v:imagedata src="cid:image009.gif@01C93EAB.55172640" o:title="ledres" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=208 height=164
src="cid:image009.gif@01C93EAB.55172640" align=left hspace=10 vspace=10
alt="LED resistor circuit" border=0 v:shapes="_x0000_s1030"><![endif]><font
size=3 face="Times New Roman"><span style='font-size:12.0pt'>An LED must have a
resistor connected in series to limit the current through the LED, otherwise it
will burn out almost instantly. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>The
resistor value, R is given by: <o:p></o:p></span></font></p>
<div align=center>
<table class=MsoNormalTable border=1 cellpadding=0>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt;font-weight:bold'>R = (V<sub>S</sub> - V<sub>L</sub>)
/ I</span></font></b><o:p></o:p></p>
</td>
</tr>
</table>
</div>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>V<sub>S</sub>
= supply voltage <br>
V<sub>L</sub> = LED voltage (usually 2V, but 4V for blue and white LEDs) <br>
I = LED current (e.g. 20mA), this must be less than the maximum permitted <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>If the
calculated value is not available choose the nearest standard resistor value
which is <b><span style='font-weight:bold'>greater</span></b>, so that the
current will be a little less than you chose. In fact you may wish to choose a
greater resistor value to reduce the current (to increase battery life for
example) but this will make the LED less bright. <o:p></o:p></span></font></p>
<h4><b><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>For
example<o:p></o:p></span></font></b></h4>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>If the supply voltage V<sub>S</sub> = 9V, and you have a red LED (V<sub>L</sub>
= 2V), requiring a current I = 20mA = 0.020A, <br>
R = (9V - 2V) / 0.02A = 350<img border=0 width=12 height=11 id="_x0000_i1032"
src="cid:image005.gif@01C93EAB.55172640" alt=ohm>, so choose 390<img border=0
width=12 height=11 id="_x0000_i1033" src="cid:image005.gif@01C93EAB.55172640"
alt=ohm> (the nearest standard value which is greater). <o:p></o:p></span></font></p>
<h4><b><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>Working
out the LED resistor formula using Ohm's law<o:p></o:p></span></font></b></h4>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Ohm's law says that the resistance of the resistor, R = V/I, where: <br>
V = voltage across the resistor (= V<sub>S</sub> - V<sub>L</sub>
in this case) <br>
I = the current through the resistor <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>So
R = (V<sub>S</sub> - V<sub>L</sub>) / I <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>For more
information on the calculations please see the <a
href="http://www.kpsec.freeuk.com/ohmslaw.htm">Ohm's Law</a> page. <br
clear=all>
<o:p></o:p></span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><a name=series></a><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt'>Connecting LEDs in series<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><!--[if gte vml 1]><v:shape id="_x0000_s1031" type="#_x0000_t75"
alt="LEDs in series" style='position:absolute;margin-left:-15pt;margin-top:-285.75pt;
width:156pt;height:176.25pt;z-index:6;mso-wrap-distance-left:7.5pt;
mso-wrap-distance-top:0;mso-wrap-distance-right:7.5pt;
mso-wrap-distance-bottom:0;mso-position-horizontal:absolute;
mso-position-horizontal-relative:text;mso-position-vertical:absolute;
mso-position-vertical-relative:line' o:allowoverlap="f">
<v:imagedata src="cid:image010.gif@01C93EAB.55172640" o:title="ledser" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=208 height=235
src="cid:image010.gif@01C93EAB.55172640" align=left hspace=10
alt="LEDs in series" border=0 v:shapes="_x0000_s1031"><![endif]><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>If you wish to have
several LEDs on at the same time it may be possible to connect them in series.
This prolongs battery life by lighting several LEDs with the same current as
just one LED. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>All the
LEDs connected in series pass the <b><span style='font-weight:bold'>same
current</span></b> so it is best if they are all the same type. The power
supply must have sufficient voltage to provide about 2V for each LED (4V for blue
and white) plus at least another 2V for the resistor. To work out a value for
the resistor you must add up all the LED voltages and use this for V<sub>L</sub>.
<o:p></o:p></span></font></p>
<p><b><font size=3 face="Times New Roman"><span style='font-size:12.0pt;
font-weight:bold'>Example calculations:</span></font></b> <br>
A red, a yellow and a green LED in series need a supply voltage of at least
3 × 2V + 2V = 8V, so a <b><span style='font-weight:
bold'>9V battery</span></b> would be ideal. <br>
V<sub>L</sub> = 2V + 2V + 2V = 6V (the three LED voltages added up). <br>
If the supply voltage V<sub>S</sub> is 9V and the current I must be 15mA =
0.015A, <br>
Resistor R = (V<sub>S</sub> - V<sub>L</sub>) / I = (9 - 6) / 0.015 = 3 / 0.015
= 200<img border=0 width=12 height=11 id="_x0000_i1035"
src="cid:image005.gif@01C93EAB.55172640" alt=ohm>, <br>
so choose R = 220<img border=0 width=12 height=11 id="_x0000_i1036"
src="cid:image005.gif@01C93EAB.55172640" alt=ohm> (the nearest standard value
which is greater). <br clear=all>
<o:p></o:p></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><b><font size=4 face="Times New Roman"><span style='font-size:13.5pt'>Avoid
connecting LEDs in parallel!<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><!--[if gte vml 1]><v:shape id="_x0000_s1032" type="#_x0000_t75"
alt="Do not connect LEDs in parallel!" style='position:absolute;margin-left:-15pt;
margin-top:-57.75pt;width:99pt;height:115.5pt;z-index:7;
mso-wrap-distance-left:7.5pt;mso-wrap-distance-top:0;
mso-wrap-distance-right:7.5pt;mso-wrap-distance-bottom:0;
mso-position-horizontal:absolute;mso-position-horizontal-relative:text;
mso-position-vertical:absolute;mso-position-vertical-relative:line'
o:allowoverlap="f">
<v:imagedata src="cid:image011.gif@01C93EAB.55172640" o:title="ledpar" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=132 height=154
src="cid:image011.gif@01C93EAB.55172640" align=left hspace=10
alt="Do not connect LEDs in parallel!" border=0 v:shapes="_x0000_s1032"><![endif]><font
size=3 face="Times New Roman"><span style='font-size:12.0pt'>Connecting several
LEDs in parallel with just one resistor shared between them is generally not a
good idea. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>If the
LEDs require slightly different voltages only the lowest voltage LED will light
and it may be destroyed by the larger current flowing through it. Although
identical LEDs can be successfully connected in parallel with one resistor this
rarely offers any useful benefit because resistors are very cheap and the
current used is the same as connecting the LEDs individually. <font color=red><span
style='color:red'>If LEDs are in parallel each one should have its own
resistor.</span></font> <br clear=all>
<o:p></o:p></span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><a name=data></a><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt'>Reading a table of technical data for LEDs<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Suppliers' catalogues usually include tables of technical data for
components such as LEDs. These tables contain a good deal of useful information
in a compact form but they can be difficult to understand if you are not
familiar with the abbreviations used. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>The table
below shows typical technical data for some 5mm diameter round LEDs with
diffused packages (plastic bodies). Only three columns are important and these
are shown in bold. Please see below for explanations of the quantities. <o:p></o:p></span></font></p>
<table class=MsoNormalTable border=1 cellpadding=0>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Type</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Colour</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>I<sub>F</sub><br>
max.</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>V<sub>F</sub><br>
typ.</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>V<sub>F</sub><br>
max.</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>V<sub>R</sub><br>
max.</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Luminous<br>
intensity</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Viewing<br>
angle</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Wavelength</span></font></b><o:p></o:p></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Standard<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Red</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>30mA</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>1.7V</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>2.1V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5mcd @ 10mA<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>60°<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>660nm<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Standard<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Bright
red</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>30mA</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>2.0V</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>2.5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>80mcd @ 10mA<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>60°<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>625nm<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Standard<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Yellow</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>30mA</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>2.1V</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>2.5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>32mcd @ 10mA<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>60°<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>590nm<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Standard<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Green</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>25mA</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>2.2V</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>2.5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>32mcd @ 10mA<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>60°<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>565nm<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>High intensity<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Blue</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>30mA</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>4.5V</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5.5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>60mcd @ 20mA<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>50°<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>430nm<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Super bright<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Red</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>30mA</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>1.85V</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>2.5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>500mcd @ 20mA<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>60°<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>660nm<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Low current<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>Red</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>30mA</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><b><font size=3
face="Times New Roman"><span style='font-size:12.0pt;font-weight:bold'>1.7V</span></font></b><o:p></o:p></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>2.0V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5V<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>5mcd @ 2mA<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>60°<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>625nm<o:p></o:p></span></font></p>
</td>
</tr>
</table>
<p style='margin:0cm;margin-bottom:.0001pt'><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<table class=MsoNormalTable border=0 cellpadding=0>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>I<sub>F</sub> max.</span></font></b><o:p></o:p></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Maximum forward current, forward just means with the
LED connected correctly.<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>V<sub>F</sub> typ.</span></font></b><o:p></o:p></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Typical forward voltage, V<sub>L</sub> in the LED
resistor calculation. <br>
This is about 2V, except for blue and white LEDs for which it is about 4V.<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>V<sub>F</sub> max.</span></font></b><o:p></o:p></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Maximum forward voltage.<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>V<sub>R</sub> max.</span></font></b><o:p></o:p></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Maximum reverse voltage <br>
</span></font><font size=2><span style='font-size:10.0pt'>You can ignore this
for LEDs connected the correct way round.</span></font><o:p></o:p></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>Luminous intensity</span></font></b><o:p></o:p></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Brightness of the LED at the given current, mcd =
millicandela.<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>Viewing angle</span></font></b><o:p></o:p></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>Standard LEDs have a viewing angle of 60°, others
emit a narrower beam of about 30°.<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><b><font size=3 face="Times New Roman"><span
style='font-size:12.0pt;font-weight:bold'>Wavelength</span></font></b><o:p></o:p></p>
</td>
<td valign=top style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>The peak wavelength of the light emitted, this
determines the colour of the LED. <br>
nm = nanometre.<o:p></o:p></span></font></p>
</td>
</tr>
</table>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><a name=flashing></a><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt'>Flashing LEDs<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Flashing LEDs look like ordinary LEDs but they contain an integrated
circuit (IC) as well as the LED itself. The IC flashes the LED at a low
frequency, typically 3Hz (3 flashes per second). They are designed to be
connected directly to a supply, usually 9 - 12V, and no series resistor is
required. Their flash frequency is fixed so their use is limited and you may
prefer to build your own circuit to flash an ordinary LED, for example our <a
href="http://www.kpsec.freeuk.com/projects/flashl.htm">Flashing LED</a>
project which uses a 555 astable circuit. <o:p></o:p></span></font></p>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>
<hr size=2 width="100%" align=center>
</span></font></div>
<h3><a name=displays></a><b><font size=4 face="Times New Roman"><span
style='font-size:13.5pt'>LED Displays<o:p></o:p></span></font></b></h3>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>LED displays are packages of many LEDs arranged in a pattern, the most
familiar pattern being the 7-segment displays for showing numbers (digits 0-9).
The pictures below illustrate some of the popular designs: <o:p></o:p></span></font></p>
<table class=MsoNormalTable border=0 cellpadding=0>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><img border=0 width=170 height=127 id="_x0000_i1041"
src="cid:image012.jpg@01C93EAB.55172640"
alt="Bargraph display, photograph © Rapid Electronics"><o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><img border=0 width=106 height=145 id="_x0000_i1042"
src="cid:image013.jpg@01C93EAB.55172640"
alt="7-segment display, photograph © Rapid Electronics"><o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><img border=0 width=137 height=191 id="_x0000_i1043"
src="cid:image014.jpg@01C93EAB.55172640"
alt="Starburst display, photograph © Rapid Electronics"><o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><img border=0 width=129 height=187 id="_x0000_i1044"
src="cid:image015.jpg@01C93EAB.55172640"
alt="Dot matrix display, photograph © Rapid Electronics"><o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Bargraph<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>7-segment<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Starburst<o:p></o:p></span></font></p>
</td>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>Dot matrix<o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td colspan=4 style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center'><font size=2
face="Times New Roman"><span style='font-size:10.0pt'>Photographs © <a
href="http://www.rapidonline.com/" target="_blank">Rapid Electronics</a></span></font><o:p></o:p></p>
</td>
</tr>
</table>
<h4><b><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>Pin connections
of LED displays<o:p></o:p></span></font></b></h4>
<table class=MsoNormalTable border=0 cellpadding=0 align=right>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal style='mso-element:frame'><!--[if gte vml 1]><v:shape
id="_x0000_s1033" type="#_x0000_t75" alt="7-segment display pin connections, photograph © Rapid Electronics"
style='position:absolute;margin-left:266.5pt;margin-top:0;width:173.25pt;
height:112.5pt;z-index:8;mso-wrap-distance-left:15pt;
mso-wrap-distance-top:0;mso-wrap-distance-right:15pt;
mso-wrap-distance-bottom:0;mso-position-horizontal:right;
mso-position-horizontal-relative:text;mso-position-vertical-relative:line'
o:allowoverlap="f">
<v:imagedata src="cid:image016.jpg@01C93EAB.55172640" o:title="pincon" />
<w:wrap type="square"/>
</v:shape><![endif]--><![if !vml]><img width=231 height=150
src="cid:image016.jpg@01C93EAB.55172640" align=right hspace=20
alt="7-segment display pin connections, photograph © Rapid Electronics"
border=0 v:shapes="_x0000_s1033"><![endif]><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'><o:p></o:p></span></font></p>
</td>
</tr>
<tr>
<td style='padding:.75pt .75pt .75pt .75pt'>
<p class=MsoNormal align=center style='text-align:center;mso-element:frame'><font
size=2 face="Times New Roman"><span style='font-size:10.0pt'>Pin connections
diagram<br>
© <a href="http://www.rapidonline.com/" target="_blank">Rapid Electronics</a></span></font><o:p></o:p></p>
</td>
</tr>
</table>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>There are many types of LED display and a supplier's catalogue should be
consulted for the pin connections. The diagram on the right shows an example
from the <a href="http://www.rapidonline.com/" target="_blank">Rapid
Electronics</a> catalogue. Like many 7-segment displays, this example is
available in two versions: Common Anode (SA) with all the LED anodes connected
together and Common Cathode (SC) with all the cathodes connected together.
Letters a-g refer to the 7 segments, A/C is the common anode or cathode as
appropriate (on 2 pins). Note that some pins are not present (NP) but their
position is still numbered. <o:p></o:p></span></font></p>
<p><font size=3 face="Times New Roman"><span style='font-size:12.0pt'>Also see:
<a href="http://www.kpsec.freeuk.com/counting.htm#drivers">Display Drivers</a>.
<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Arial><span style='font-size:10.0pt;
font-family:Arial'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><strong><b><font
size=5 color=navy face=Arial><span style='font-size:18.0pt;font-family:Arial;
color:navy'>“ </span></font></b></strong><strong><b><font color=navy
face=Arial><span style='font-family:Arial;color:navy'>Não me mande os meus
"e-mails" de volta - eu já os vi!</span></font></b></strong><strong><b><font
size=5 color=navy face=Arial><span style='font-size:18.0pt;font-family:Arial;
color:navy'> “</span></font></b></strong><font color=navy><span
style='color:navy'> <o:p></o:p></span></font></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=3 color=navy face="Times New Roman"><span style='font-size:12.0pt;
color:navy'> </span></font><font size=2 color=black face=Arial><span
style='font-size:10.0pt;font-family:Arial;color:black'>Blog: </span></font><font
color=navy><span style='color:navy'><a
href="http://carlosfonseca-ct1gfq.blogspot.com/"
title="http://carlosfonseca-ct1gfq.blogspot.com/">http://carlosfonseca-ct1gfq.blogspot.com/</a></span></font><o:p></o:p></p>
<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><font
size=2 color=black face=Arial><span lang=EN-GB style='font-size:10.0pt;
font-family:Arial;color:black'>Photos: </span></font><font color=navy><span
style='color:navy'><a href="http://www.flickr.com/photos/9018639@N04/"
title="http://www.flickr.com/photos/9018639@N04/"><span lang=EN-GB><span
title="http://www.flickr.com/photos/9018639@N04/">http://www.flickr.com/photos/9018639@N04/</span></span></a></span></font><font
size=2 color=black face=Arial><span lang=EN-GB style='font-size:10.0pt;
font-family:Arial;color:black'> </span></font><font color=navy><span
lang=EN-GB style='color:navy'>( New update: <strong><b><font
face="Times New Roman">28/</font></b></strong>Out./2008 )<o:p></o:p></span></font></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
</div>
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