# PWM setup

Discussion in 'LEDs and Optoelectronics' started by NeilMac, Aug 28, 2018.

1. ### BobK

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Jan 5, 2010
Red LEDs are not 3.2 to 3.4V. The are typically 2.5V.

Bob

2. ### NeilMac

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Aug 28, 2018
Their not red, UV-a / Royal blue / Full spectrum. (1W)

3. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,505
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Jan 21, 2010
Your picture shows red. If you post a picture and something is clearly rendered incorrectly it would help a great deal if you say so.

My advice about reading the forward voltage still stands. (Also about how you should calculate the string voltage and match it to the driver)

4. ### NeilMac

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Aug 28, 2018
I got my 10W leds (IR850nm) working no problem.

The 1W leds are still being a pain in the ass, tried three different drivers and incorporating 3-15 leds, best was four seconds of light before flashing. Even tried using just one type in a string.

This amount produced the longest activation.

5. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
We can do no more until you spend \$5 on a cheap multimeter.

6. ### NeilMac

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Aug 28, 2018
Got a meter..
33v (bouncing)(analog meter) with 12leds, 4x3 in parallel so the current is max of 1.05-1.14A.
Still flashing and only the first three rows light up, fourth nothing.

7. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Great, you have a meter

Now measure the forward voltage of each different type of LED.

Also, don't put the LEDs in parallel. Odd things can happen.

8. ### NeilMac

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Aug 28, 2018
So the led current and the driver current out put difference does not matter?

9. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Yes it matters a great deal. If you need multiple strings in parallel then you'll need to ensure the current is equally shared. A resistor in each string will help.

Something that drops a couple of volts should be sufficient. 2W 6.8Ω resistors should work fine (they will drop 2.4V at 350mA).

So, what is the MEASURED forward voltage of your LEDs?

10. ### NeilMac

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Aug 28, 2018
Haven't gotten back to it, a frustrating several hours this morning mix and matching, roasted Coffee Beans to relax for a bit before I get back to it

11. ### NeilMac

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Aug 28, 2018
So I sorted out the system, after trials and errors and lots of profanity. I found the DC-DC converts work without a problem. SO non of the ACDC drivers worked, except with the 10w LEDs.

12W as in 12x 1W led's powered by 12V in this case and running at 280ma aprox. Three in parallel. Full Spectrum Versions.