## Step 5: Test the Polarity of the Wires

before we solder up the last connection to the LED's we need to check the polarity of the supply tracks, as LED's are polarity specific.
a quick reconnection to the vehicle and test the wire's onto the LED's and remember which way round they go.
<p>I got my LEDs from EnlightenOz, they have LEDs built into bases that fit right into the original socket! They have a Facebook page here: <a href="https://www.facebook.com/enlightenoz" rel="nofollow"> www.facebook.com/enlightenoz</a></p>
Some things you may wish to add to your article.<br> <br> What diameter LED you used. The ones you used seem to come in 5 and 8mm sizes.<br> <br> What Ohm value resistor you used. You stated the correct Watt range but never the resistance value.<br> <br> A more sure fire way to determine LED polarity. One easy way is seeing which lead is shorter. The shorter one is the cathode.<br> <br> With apologies to Will:<br> <br> To big, or not too big, that is the hole question!<br> <br> <a href="http://www.educationbug.org/a/to-vs--too.html">http://www.educationbug.org/a/to-vs--too.html</a><br> <br> Personally I like cars better after all their dash lights burn out :)
hi!<br>i use 8mm LED's which i buy with the correct resisters to run on 12volts, its cheaper than buying them seperatly and easier for those who dont know how to work resistance values. Mine are 2w 100ohm resisters.<br><br>R = (VS - VL) / I <br>VS = supply voltage <br>VL = LED voltage (usually 2V, but 4V for blue and white LEDs) <br>I = LED current (e.g. 10mA = 0.01A, or 20mA = 0.02A) <br><br>The polarity you need to check is the dash unit as the tracks are not normaly marked. sorry if that was not clear.<br><br>Perhaps i will do an instructable on basic LED science
No it wasn't clear to me when what you said was, &quot;<em>before we solder up the last connection to the LED's we need to check the polarity as LED's are polarity specific.</em>&quot;&nbsp; Check the polarity of what? The last thing you mentioned was LED. I am a contextual reader. Rereading it knowing the polarity you mean is the supply polarity it all makes sense. It didn't the first time I read through it though. Well, it did make sense to me, just not what you meant.<br> <br> <br> I'd like to see how the math is figured for a 100 Ohm resistor running an LED off 12 volts. So write that LED science article! Are your LEDs 80ma? The ones I was looking at online seemed to be about 20ma. Yours must be really bright!<br>
hi, the LED's are 3v forward voltage, 100ma forward current.<br>yes they are realy bright!!<br><br>search eBay for &quot;strawhat led 8mm&quot;<br><br>the ones i use are 0.5w
I bet they are bright. Have you measured your current draw with a multimeter? What the hey it is working for you good luck!