Current Limit Resistor Calculator

[rWAVE]

Came across this in another forum. It might be useful to help some folks calculate current limit resistors values when driving various LED types with a user-defined power source:

http://hackaday.com/2013/01/14/papercraft-dial-is-the-slide-ruler-of-current-limiting-resistors/

Richard

 

[goom]

I have an Excel spreadsheet that I wrote to calculate resistor values based on:
Forward voltage (user specified or typical based on color selection)
Number of LED'd
Supply Voltage
Current
Output gives closest 2%, 5% and 10% resistor values, color codes and minimum W rating.
I'd be pleased to share it, but have no idea how to post it to provide access. If of interest, perhaps someone could help to disseminate it.

 

[boriz]

I find Ohms law and a calculator works just fine.

 

[westaust55]

Valid file extensions: bas bmp cad doc dsn gif jpe jpeg jpg pdf plf png psd txt zip

CLick the "Go Advanced" button at the bottom right and then the paper clip icon in the top row of the post toolbar to access the Atatchment manager.

you would need to make the file extension say .dsn before it could be uploaded.

 

[BeanieBots]

I find Ohms law and a calculator works just fine.

Not sure you even need the calculator.
LEDs are not very critical and an estimation to the nearest prefered value will nearly always suffice.
For hobby work more often than not I end up using whatever resistor I have the most of that is remotely close.
For paid work, I use a set of well established values depending on colour and 'standard' rail voltage.

 

[srnet]

I find Ohms law and a calculator works just fine.

Absolutly.

In the time it takes to build or even use a a 'LED Current Limit Calculator' you can do it with a calculator.

Maybe of benefit to those who dont know Ohms law, but then those people would benefit from learning it.

 

[nick12ab]

I have an Excel spreadsheet that I wrote to calculate resistor values based on:
Forward voltage (user specified or typical based on color selection)
Number of LED'd
Supply Voltage
Current
Output gives closest 2%, 5% and 10% resistor values, color codes and minimum W rating.
I'd be pleased to share it, but have no idea how to post it to provide access. If of interest, perhaps someone could help to disseminate it.

There's no need to change the file extension of unsupported filetypes anymore as you can now upload zipped folders and that has the advantage of compressing the file so that the 976.6KB file size limit is used effectively.

The only supported format that has a bigger file size limit is .txt with a limit of 1.91MB so if your file is 2.5MB and putting it in a zipped folder only compresses it to 1.5MB then you can change the extension of the zipped folder to .txt but if it compresses it to 0.8MB then there's no need to change the extension.

I think it's always best to avoid changing the extension where possible because when I once uploaded a video by changing the file extension to .pdf and I stated in the post that the extension had to be changed, a member complained that the PDF didn't work.

 

[goom]

I recognise that calculating resistor values for LED current limiting is not a great challenge to most of those who frequent this forum. However, I devised the spreadsheet to help out people who are graduating from incandescent to LED lighting on their model boats. Some of these people are octogenarians, and many have little or no knowledge of electronics.
Here it is, for what it is worth. Two versions for the older and newer Excel versions. I like the newer one as it shows the resistor bands as actual colors rather than just words. Feel free to use, abuse, distibute at will.

 

[fernando_g]

I agree with you goom. I also have done a few spreadsheets to easily calculate simple tasks...is part of the tools in my software "toolbox".

 

[Haku]

I really like this site for calculating resistor values: http://led.linear1.org/led.wiz
As it caters for single/multiple LEDs from a single power source.