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Part 4042 / Defective or wiring problem?
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Part 4042 / Defective or wiring problem?

by bkeyport on Fri Nov 20, 2020 9:38 pm

I purchased the DIFFUSED RED AND GREEN INDICATOR LED - 18MM ROUND.

It works, except for when the Red line is connected to *anything*, on or off, it'll turn on if either input is on.

Red high, Green Low = Red On, Green Off
Red High, Green High = Red On, Green Off
Red Low, Green High = Red On, Green Off
Red Low, Green Low = Both off.

Capture.PNG
Capture.PNG (13.56 KiB) Viewed 112 times


This is my wiring for it. The transistor circuit was prebuilt from a previous LED driver.

Is it defective, or is my wiring messed up?


Thanks!

bkeyport
 
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Re: Part 4042 / Defective or wiring problem?

by dastels on Fri Nov 20, 2020 9:51 pm

Try putting a limiting resistor on each of the red and green pins instead of on the common cathode.

Dave

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Re: Part 4042 / Defective or wiring problem?

by bkeyport on Wed Nov 25, 2020 2:15 am

dastels wrote:Try putting a limiting resistor on each of the red and green pins instead of on the common cathode.


That seems to have done it in tests. Now to figure out good resistor values to even out the extremely bright green and very weak red.

Edit: Found them. For me, it's 220ohm for red, 1kohm for Green, produces a nice yellow when combined, and a nice dull (Non-distracting) color for each of the LEDs otherwise.

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Re: Part 4042 / Defective or wiring problem?

by dastels on Wed Nov 25, 2020 10:23 am

220 ohm is my default choice. Sometimes 330 ohm for green and blue. It depends on the LEDs and the brightness you desire.

Dave

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Re: Part 4042 / Defective or wiring problem?

by bkeyport on Sun Nov 29, 2020 12:29 am

So, Yeah. Put it into the live circuit, and back to failures. It'll now come up yellow if both sides are connected to the circuits. I believe that as soon as something is common, it fails..

Officially not recommended product. I'll be using the one side, and abandoning the other.

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Re: Part 4042 / Defective or wiring problem?

by dastels on Sun Nov 29, 2020 11:32 am

I'm having trouble understanding what you are saying. It should be yellow if both diodes are powered. red + green = yellow (for light). It's 2/3 of an RGB diode.

Dave

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Re: Part 4042 / Defective or wiring problem?

by bkeyport on Sun Nov 29, 2020 10:09 pm

If both the red and green LEDs are connected to their circuits via my pi, if they have power or not, they'll both light, as if there's a short across the LED lines.

This does not occur with any other RGB LED I have. Like I've said, I've given up on dealing with it, and will only be using the green circuit, and using my arcade button's LEDs for the function I was gonna use the red LED side for, as it don't conflict.

bkeyport
 
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Re: Part 4042 / Defective or wiring problem?

by dastels on Sun Nov 29, 2020 10:53 pm

Hmm. But it works fine in a test circuit? Just not when hooked to the Pi?

Dave

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Re: Part 4042 / Defective or wiring problem?

by bkeyport on Sun Nov 29, 2020 11:00 pm

The test circuit is a copy of the final circuit, run through a test pi. Only difference between the two is the final is on a PCB, and the test is on a breadboard - and I do think I'm using different GPIOs on the test, but that shouldn't matter.. Like I said, it does not occur on the test RGB led I built up identical to see - the test RGB works as expected on either circuit.

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Re: Part 4042 / Defective or wiring problem?

by dastels on Mon Nov 30, 2020 11:26 am

Weird. That the RG LED works in one circuit and not the other leads me to think the problem isn't with the LED, itself, but some other difference in the circuit.

Dave

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Please be positive and constructive with your questions and comments.