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Old 01-17-2022, 02:46 AM   #21
eccerr0r
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Default Re: LED Array Schematic Check?

Nothing wrong with fluorescent tubes, I don't mind them at all. A lot easier to service than LED, then again the hope is that LEDs never fail. But look at all those TVs...
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Old 01-17-2022, 03:12 AM   #22
EasyGoing1
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Default Re: LED Array Schematic Check?

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Originally Posted by eccerr0r View Post
Nothing wrong with fluorescent tubes, I don't mind them at all. A lot easier to service than LED, then again the hope is that LEDs never fail. But look at all those TVs...
Right? And even this lamp that I bought lasted all of 8 months before the LEDs in it started flickering out and I had to replace them ... after the third time replacing them and it started in with its flickering crap again, I had enough of it and decided to make this board which ... I expect ... will last a lot longer since the design seems more stable to me than what it shipped with ... and so far I only run the lamp at 50% on the dial until I need to use the magnifying glass then I crank it up to 100% but the lamp stays on all the time ... just at 50% in between actual use of the lamp.

I never have found a fluorescent magnifying lamp that could produce the lumens that I can get with LEDs.
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Old 01-17-2022, 03:21 AM   #23
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Default Re: LED Array Schematic Check?

I have a generic question that maybe one of you can answer ...

Consider the original question I had where I talked about using a potentiometer as the brightness adjuster for this circuit ... based on the calcs I was seeing, when I was going to use straight DC voltage for this circuit, I would have had to use a pretty fat POT as the brightness adjuster since it appeared that quite a lot of current would be running through that pot....

Given that PWM is technically more efficient than using straight voltage ... what would the results be of implementing an RC filter at the output of a PWM source? Then adding a pot at that point for brightness adjustment? Would it bring it back to the original problem where the current would be such that the pot would have to be more robust or would the fact that the source voltage is simply filtered PWM mean that the calcs should be different given that the source is different than a straight DC source?

This question is purely academic by the way ... I'm just curious.
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Old 01-17-2022, 05:29 AM   #24
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Default Re: LED Array Schematic Check?

Depending on how the PWM signal is generated it might make a difference but I am not sure exactly because when I had to do this for an industrial application the PWM was generated by a micro controller and with type of signal this is very noisy environment and putting a small value capacitor on the output cleaned it up enough that the device worked correctly this is what I am going by but when I look at the volt meter with out the capacitor on the output you could see the voltage fluctuation with your eyes but after putting the capacitor on the output it smooth out the voltage fluctuation and was less notable
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Old 01-18-2022, 06:38 PM   #25
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Default Re: LED Array Schematic Check?

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Originally Posted by sam_sam_sam View Post
but when I look at the volt meter with out the capacitor on the output you could see the voltage fluctuation with your eyes but after putting the capacitor on the output it smooth out the voltage fluctuation and was less notable
Which reminds me ... I need to look at the output of this PWM dimmer with the cap on it with the scope ... curious to see what it looks like.

Here are some screenshots of the scope when I had the PWM dimmer connected to 19 volts then the output was connected directly to the scope (not under load at all).







If I'm not mistaken, the phantom traces in that third image, which are clearly distinguishable from the real signal ... is a result of the scope being unable to lock onto the signal thoroughly because the signal is so crappy in the first place.
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