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Resistor value question


scubado
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Does somebody have a calculator link that can help me with this question?

 

36V power supply

10 leds in series

700ma circuit.

 

I want to replace 1 led with a resistor, I want to find that value and watt rating.  I have a couple resistor calculators, but they aren't setup for this kind of question.

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Does somebody have a calculator link that can help me with this question?

 

36V power supply

10 leds in series

700ma circuit.

 

I want to replace 1 led with a resistor, I want to find that value and watt rating.  I have a couple resistor calculators, but they aren't setup for this kind of question.

 

 

 

I believe this is the one that will help you with your calculations: http://ledcalculator.net/default.aspx?lang=en-GB

EDIT: Ugh, it won't work, max voltage for this calculator is 24V, so it won't do what I thought it would.

 

I did have this one bookmarked {probably the one I used}, not sure if it will help or not: http://www.hobby-hour.com/electronics/ledcalc.php

But this one allows any voltage you need.  But it's set mainly for single color strands, there is an "other" option in the colors, whether or not that would work for multi-color I can't say.

 

But maybe this second one will help, I tested it with voltages from 2v to 240v for the supply voltages, just need to know the mA rating of the LED, color/voltage drop, number of LED's and what resistor precision you want to use.

 

I've used this one to fix bad LED strands that had bad sockets I needed to remove and converted to a single color strand.

Edited by Orville
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Thanks Orv,  exactly what I was looking for.  I have a couple lighting projects coming up soon that this may come in handy.  Planning on converting my kitchen lights.

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dont need no stinking calculator for this one. 36 volts divided by 10 = 3.6V per LED. Now I have no idea where the 700ma come from, but will work with your number. To find resistance value of the single LED, take voltage and divide by current of 700ma.  3.6 / .7 = 5.1 ohm. Now for the power or wattage rating of the resistor. P=E*I or 3.6 * .7 = 2.52 Watts.

Are these really high wattage LEDs your playing with? For the most part we are working with LEDs that only draw 20ma.

Edited by Max-Paul
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Thanks Orv,  exactly what I was looking for.  I have a couple lighting projects coming up soon that this may come in handy.  Planning on converting my kitchen lights.

Glad it will work for you Jim.   I used it to set up LED lights that I wanted to shrink the strand to fit around a room for mood lighting and watching TV without having the overhead light on {that glares in the TV screen} or regular lamps, just enough white LED light to see by, but not be overpowering..

 

So it should work well for your kitchen lighting project, as well as others you'll now come up with.

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dont need no stinking calculator for this one. 36 volts divided by 10 = 3.6V per LED. Now I have no idea where the 700ma come from, but will work with your number. To find resistance value of the single LED, take voltage and divide by current of 700ma.  3.6 / .7 = 5.1 ohm. Now for the power or wattage rating of the resistor. P=E*I or 3.6 * .7 = 2.52 Watts.

Are these really high wattage LEDs your playing with? For the most part we are working with LEDs that only draw 20ma.

Yes, I'm working with 3w leds.  I am very happy with the turn out of converting two large fish tanks to led lighting.  I'll have a third one done this weekend and order more leds for the forth one and then start on the kitchen.

 

For anyone wanting to do this, 10 leds in series with the power supply tweaked to 34V

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