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Feature request: LED testing with specific current #2

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seanspotatobusiness opened this issue Aug 29, 2018 · 2 comments
Open

Feature request: LED testing with specific current #2

seanspotatobusiness opened this issue Aug 29, 2018 · 2 comments

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@seanspotatobusiness
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I have a request for a feature for LED testing. Sometimes I'd like to determine the voltage to apply to an LED to get a current of e.g. 5, 10, 15 or 20 mA so it would be nice to have a function where I can set the amount of current I want to flow and the tester tells me what voltage this happens at. Is that possible? Thanks.

@gojimmypi
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@seanspotatobusiness I'm not sure anyone will see your idea; this repo is a

GitHub clone of SVN repo svn://mikrocontroller.net/transistortester/

(I don't know if even PR's work here?)

See http://svn2github.com/about/

@bonac
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bonac commented Oct 6, 2018

I have a request for a feature for LED testing. Sometimes I'd like to determine the voltage to apply to an LED to get a current of e.g. 5, 10, 15 or 20 mA so it would be nice to have a function where I can set the amount of current I want to flow and the tester tells me what voltage this happens at. Is that possible? Thanks.

This will not run like this. LEDs are always current driven, i.e. need a current source and not a voltage sours, i.e. there is no way you can apply a constant voltage and it will consume the "calculated" corresponding current. If you apply a tension source due to natural LED heating it will eat more and more current and will die in thermal runaway.
LED usage is the same: get the current rated for the LED from the datasheet (classical RGGBO ones are ~20mA, except special ones and white are much more), get the Fwd Voltage of the LED, which the TransistorTester is giving :-), then choose your voltage supply and calculate the resistor you need to add R=(Vpower-VFwd)/I to build the current source.
It is you choice to under run or slightly overrun the device.
And the TransistorTester has no idea of the max current a LED can sustain, so it can't help.
The only possible things is to add a source current feature and allow you to have an idea of the LED brightness you like, and touch it to make sure it is not too hot ;-)

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