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#1 |
Shock Therapist
Join Date: Sep 2016
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![]() Was wondering if someone would double-check my design here. It's relatively simple. I used an online LED array calculator to get the core array specs. And for the potentiometer, I figured that since the sum of the parallel resistors (since I don't know the internal resistance of the LEDs) is 5.5 Ohms, that adding a 5 ohm pot for dimming would be sufficient, if not overkill possibly.
Each LED is rated at 3.2V 150ma VCC = 19V from a laptop power supply, so it should be a fairly stable source voltage. I need the thing to be stable and to be able to dim it. Does this design seem like it would fit that requirement? ![]() And here is the PCB layout, front and back.... ![]() ![]()
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Last edited by EasyGoing1; 12-26-2021 at 03:45 PM.. |
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#2 |
Badcaps Veteran
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![]() You could also use a PWM controller to dim the LEDs I have done this in the past you might need to use a filtering capacitor on the output so you do not see the switching of the PWM controller ( these controllers are very inexpensive to buy )
Because I also am going to use a LED yard light with a PWM controller to set to a certain brightness to save on battery power and not use a resistor to control them Another option is use a switching power supply that can be adjustable voltage output I have a couple of them and they work pretty good and they are the same size as a laptop charger
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9 PC LCD Monitor 6 LCD Flat Screen TV 30 Desk Top Switching Power Supply 10 Battery Charger Switching Power Supply for Power Tool 6 18v Lithium Battery Power Boards for Tool Battery Packs 1 XBox 360 Switching Power Supply and M Board 25 Servo Drives 220/460 3 Phase 6 De-soldering Station Switching Power Supply 1 Power Supply 1 Dell Mother Board 15 Computer Power Supply 1 HP Printer Supply & Control Board * lighting finished it * These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10% 1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later ) 2 Hem Saw Computer Stack Board All of these had ![]() All of the mosfet that are taken out by bad caps ![]() Last edited by sam_sam_sam; 12-26-2021 at 03:53 PM.. |
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#3 | |
Shock Therapist
Join Date: Sep 2016
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#4 | |
Shock Therapist
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#5 |
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![]() You don't get flicker with those PWM controllers. I have the identical ones but bought from Ali at about the third of the price.
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#6 |
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![]() Note you would not need R5 if used the PWM controller if you did it correctly you might need not need R1 to R4 you need to do some testing on the PWM controller that you use and see if those resistors are not need or you might less resistance values than what you have on your diagram now
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#7 | |
Shock Therapist
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No resistors at all, hu? That sounds risky. Last edited by EasyGoing1; 12-29-2021 at 04:36 AM.. |
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#8 | |
Shock Therapist
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#9 |
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![]() Are you sure that you do not have it hooked up backwards because I have done this myself before
I see that this board is marked the ones I have are not marked very well so it is to hook them up backwards Yes this should work just make sure that you have a current meter hookup so that you do not over drive the LED array unless you want to change the brightness then you have a little bit more work to do then you need to find out what the resistance is on the pot ones you have reached the maximum current or less than the maximum current and that is allowed for the LED array then put a resistor on the top end of pot so that when the pot is maxed out this your maximum current you want to have on this LED array I hope this helps you with what you want to do Last edited by sam_sam_sam; 12-29-2021 at 10:22 AM.. |
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#10 | |
Shock Therapist
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Anyways ... it was basically a bust all around ... I decided to just order another one, assuming got a bad apple from the bunch ... and they're only like $6 ... people pay $15 for a pack of cigarettes these days ... no idea how people can afford to smoke. lol Last edited by EasyGoing1; 12-29-2021 at 11:26 AM.. |
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#11 |
Shock Therapist
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![]() So I got the new unit today from Amazon, and it worked right out of the gate ... and surprisingly it works quite well in spite of the fact that when I connect it to the scope, the signal is dirty as all hell. That was the first thing I connected it to and looking at that shitty signal I did not expect it to work at all ... but ... it does ... and amazingly well so I'll be using this for sure as the dimmer for my circuit. Though I'm leaving the series resistors in the circuit ... certainly can't hurt ... but I won't be using the resistor/pot that I originally asked about.
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#12 |
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![]() See if you add a small value capacitor to the output make the power supply output cleaner and smoother
I have used this approach for a dc volt solenoid amplifier controller that I used to control a solenoid valve with a PWM controller because the machine controller went partially bad and I still need the machine to keep working with a partially malfunction machine controller Last edited by sam_sam_sam; 12-31-2021 at 12:51 AM.. |
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#13 | |
Shock Therapist
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#14 |
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![]() Let us know how this works and if you can post a picture of it when it is finished
Oh by the way what is this made for |
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#15 |
Shock Therapist
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#16 | |
Shock Therapist
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![]() ![]() Should be obvious now what its for... it is replacing the stock circuit board on this lamp that I'v grown rather fond of over the years. The PWM device is being fed 19 volts but only 17 are reaching the circuit at max volume ... I put a 1k µF cap on it for now cause that's what I had in the immediate vicinity... not impressed with the brightness but at only 17 volts that explains why. I think the PWM device has its own voltage drop that is possibly consuming that 2 volts so i gotta find a way to feed it like 21 volts or something so ˆ*can get 19 at the output. Last edited by EasyGoing1; 01-13-2022 at 11:03 AM.. |
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#17 |
Shock Therapist
Join Date: Sep 2016
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![]() So I realized my thinking was all wrong on the voltage issue... I didn't need to give it more voltage, I needed to give it less resistance. So I ran the numbers for a 17V source and the resistor value came back at 6.7-ish ... all I had in an SMD package was a 7 ohm ... PERFECT! So I replaced the resistors with the 7Ohm and the light is much brighter now and surprisingly does not put out a lot of heat which I am just elated about that. At max volume, you couldn't hold onto the LEDs for very long, but certainly not burning hot and at ½ to ¾ volume, they hardly get warm with plenty of usable light.
And here are photos looking through the magnifying glass, without the light on and then with the light on at full blast ... but the photos don't really do it justice. ![]() ![]() |
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#18 |
Badcaps Veteran
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![]() Nice work
I need to need to redo a fluorescent magnifying glass that is to heavy for the flex rod which is not long enough to begin with and use LED lights instead but I am not very good designing circuit boards Last edited by sam_sam_sam; 01-13-2022 at 09:27 PM.. |
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#19 |
Solder Sloth
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![]() The brightness should assist in depth of field in the camera - if it supports it.
Sigh. Unfortunately most cameras do not these days as it'd increase their thickness... I'm still using fluorescent bulbs in my magnifier lamp and probably won't stop until they can't be had easily anymore. Though I should figure out why it seems to be sputtering filament onto the ends so quickly. I suppose it's a problem with running these tubes CC with its electronic ballast. |
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#20 | |
Shock Therapist
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