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IR strobe light

alwaysanoob

New Member
Hello. noob here. I don’t know what i'm doing, and am looking for help.

I'm trying to make an IR strobe light with a cheap light source and a PWM.

Illuminator: https://www.amazon.com/Illuminator-...1&keywords=ir+ledmarray&qid=1615128729&sr=8-7

PWM: https://www.amazon.com/PEMENOL-Gene...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

The illuminator power supply is DC 12V/1A

The PWM is DC 3.3-30V 1Hz-150KHz 8A.

Can I achieve my desired strobing effect by simply connecting the power supply output to the PWM, and then the PWM output to the illuminator?

Thankyou in advanced for your help and patience.
 

audioguru

Well-Known Member
Most Helpful Member
The IR LEDs have no detailed specs and have no detailed datasheet describing the max allowed peak current at various pulse widths because Amazon and their sellers are not engineers. The IR LEDs in a remote control have a detailed datasheet because they are made for high current very bright pulses of IR.

This illuminator is probably not made to be a very bright IR strobe light, just an ordinary continuous IR light. High current pulses will probably burn it out.
If its power supply voltage is more than 12V then the current will be higher, it will be brighter and it will burn out sooner.
 

gophert

Well-Known Member
Most Helpful Member
It is a 12VDC, 8 watt illuminator could work. One challenge will come if there are any significant sized capacitors across the power supply. Trying to flash faster than the capacitor can charge/discharge will cause the sharp edge of on/off to be less sharp and eventually not turn off completely or on completely if it is too fast. You could open it up and remove the decoupling capacitor if needed. It is only there to stabilize the intensity.
 

alwaysanoob

New Member
Thank you for the replies.
My primary concerns were - will the input power kill the PWM / will the PWM output enough power to run the illuminator.
This issues you bring up didn't even occur to me.

Not sure I understand the power supply issue, since the power supply will be feeding into the PWM. So it wont see the modulation frequency.

My plan is as follows (sorry it wasn't clear):
Wall outlet -> 12V/1A power adapter-> PWM -> Illuminator

FWIW the PWM will be set to 40Hz, 50% duty cycle.
In any case; if you can recommend a more suitable LED panel and/or power supply, I'm open to suggestions.

Thanks again!
 

gophert

Well-Known Member
Most Helpful Member
I was talking about the possible presence of capacitors across the 0 (ground) and 12V power inside the IR illuminator That could cause the rising edge of the voltage to slow.
How fast do you need this strobe to flash?

the PWM controller should be ok if it can a
Provide 1 amp or more (the lamp needs only 0.67 but better safe to have a little excess.
 

shortbus=

Well-Known Member
Most Helpful Member
Maybe explaining why you need IR strobe would get better ideas. AG I think hit the big thing about burning out the LEDs by strobing.
 

alwaysanoob

New Member
gophert ; got it. thanks. I'll splurge $15 on the illuminator and open it up in search of caps.
I don't have a way to monitor the squareness of the pulses though. I'll be pulsing at 40hz, 50% duty cycle.

shortbus= The following example articles will provide elucidation as to my motivations:

A cell phone camera will let me see whether not the LEDs burn out.
If there is a better panel/array i should consider; let me know.
I can buy individual NIR LEDs at digikey or mouser; but i don't really want to assemble my own panel.
 

gophert

Well-Known Member
Most Helpful Member
I’m interested in your result. The light used in the paper was 810nm wavelength. A “bright” one will have a significant visible red emission. The peak wavelengths of the light you listed is 850n and a higher power LEDs will have a faint red glow that human eyes can see.

gt
 
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shortbus=

Well-Known Member
Most Helpful Member
Just my suggestion, instead of strobing the light panel you could make a disc with a cut out section in it. This disc would then be rotated with a motor, a DC motor with speed control, so the strobe time could be varied. This would all be placed in front of the IR panel. By doing it this way the IR leds are on constant and only the speed of the rotating disc would be the strobe pulse factor.

That panel to me seems like it is pretty big, but I didn't look for a size on it, maybe the smaller round one in that link might work?
 

alwaysanoob

New Member
shortbus= A chopper wheel is s good idea, and would definitely work. It guatanties a clean square pulse. But it adds a level of complexity and clunkyness that I'm trying to avoid for now.

The illuminator has a faint red glow that is clearly visible to the naked eye. It looks very bright to a cellphone camera. Pulsing at 1hz to 10hz, all looks good. At 25+ hz, i don't really see any pulsing, even though i should be able to easily see that flash rate. so gophert was probobly cortect about componants not keeping up with the pulse frequency.

A picture of the lluminator's brains are attached. It's not obvious to me what this does. I'm tempted to bypass the board by plugging (a) directly into (b).
I unplugged (c) so that on/off isn't controlled by room britness.

20210312_155704.jpg
 

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