Repurposing Laptop/Electronics power supplies

[sumg]

Hi Folks, been lurking here a bit, recently built a 10x Gen2 EB strip build, and have a little more confidence in their usefulness to my goal of a nice herb bed, lettuces, etc.

Since I'm cheap I happen to enjoy the idea of repurposing most of my old laptop adapters, and weird electronic power supplies that come my way. I know the midpower stuff slots in around the voltages I tend to lay hands on


Given these aren't LED drivers, they're just standard power supplies. aside from matching up the voltages and always ensuring I run far more strips than watts supply can provide, any suggestion for a cheaper way to add some actual control of the current? Some of the buck converters I see look pretty sketchy, prefer more of an enclosure type unit, but cheap.

I've got a 24VDC 90W supply from a cpap machine, and a few old 19v laptop adapters for long dead laptops of varying wattages. The cannabis cabinet gets mean well, but I figure if I have some nice open airflow areas that just need some bright lights for a bit a day, I can cobble something pretty safely.

totally open to suggestions, thanks all.
Oh, and I'm up here in Canada, so the usual hard to source stuff applies.

[bvolt]

If you're comfortable working with power, I wouldn't worry about that at all.

If you need to decrease (buck) your voltage just buy a quality LM2596 board. For boost, go with XL6009.

If you look around, you can find one with an onboard meter (volts and/or amps), for $8-12. Sharp eyes might find a CC pot.

Good luck.

[bvolt]

This looks promising....

Amazon Listing




CC/CV fully adjustable using a knob (usually you just get a pot).

The M1 & M2 buttons can even "recall" specific DC output voltages (when unit disconnects from power, the output voltage switches back to the default 19V).

For your build, just create a small recess in your enclosure or the wall of your frame, pop it in and wire it up.

[sumg]

Thanks!

The amazon link led to more links to something better suited for my uses (and available in Canada), but I had no idea these existed in this form. Can't wait to build a new light with a slick power module.

[LEDG]

Thanks!

The amazon link led to more links to something better suited for my uses (and available in Canada), but I had no idea these existed in this form. Can't wait to build a new light with a slick power module.

What'd you end up going with?

[electrok-d]

This thread is exactly what I registered a forum account to inquire about! I have a lot of computer power supplies that range from 400 to 600 watts. One thing that I haven't been able to figure out, which also isn't covered in this thread, is how to determine if the power supplies are constant voltage or constant current.

Any thoughts on this or how to determine it by looking at the specs on the supplies or any other random power supplies out there?

[MoosingAround]

This thread is exactly what I registered a forum account to inquire about! I have a lot of computer power supplies that range from 400 to 600 watts. One thing that I haven't been able to figure out, which also isn't covered in this thread, is how to determine if the power supplies are constant voltage or constant current.

Any thoughts on this or how to determine it by looking at the specs on the supplies or any other random power supplies out there?

Laptop power supplies are Constant Voltage. The one I'm plugged into now is 20v DC up to 6.75 amps.
Most standard household power supplies are going to be Constant Voltage. USB chargers are 5 volts, with older models supplying max 500mA. Id expect any consumer electronic with a DC barrel jack to be constant voltage (alarm clock, electric razor, bluetooth speaker) probably 12v or 24v.

On the attached pic, the red circle shows you your OUTPUT (20 volt DC @ max 4.5 amps), and the blue circle shows you the setup of the DC barrel jack (some have + in middle, some have -)

Now just because it says 20v doesnt mean you can connect it directly to say an BXEB gen 2 strip (18.5v - 20.5v) and expect it to stay steady at 20.0 volts. A laptop has internal circuitry to deal with variance from the power supply, an LED wont. I'm sticking with Meanwell HLG power supplies so that I don't have to worry about it.

[electrok-d]

Laptop power supplies are Constant Voltage. The one I'm plugged into now is 20v DC up to 6.75 amps.
Most standard household power supplies are going to be Constant Voltage. USB chargers are 5 volts, with older models supplying max 500mA. Id expect any consumer electronic with a DC barrel jack to be constant voltage (alarm clock, electric razor, bluetooth speaker) probably 12v or 24v.

On the attached pic, the red circle shows you your OUTPUT (20 volt DC @ max 4.5 amps), and the blue circle shows you the setup of the DC barrel jack (some have + in middle, some have -)

Now just because it says 20v doesnt mean you can connect it directly to say an BXEB gen 2 strip (18.5v - 20.5v) and expect it to stay steady at 20.0 volts. A laptop has internal circuitry to deal with variance from the power supply, an LED wont. I'm sticking with Meanwell HLG power supplies so that I don't have to worry about it.

It seems that some higher end computer power supplies offer internal voltage regulation. Take this monster for instance :

https://www.amazon.com/Corsair-AX1500i- ... Z3T09RER8R


Here is a excerpt from it's specs:

" Digitally controlled power

The AX1500i is designed around a DSP for increased efficiency, tighter voltage regulation, and superior electrical specifications. The elegant, DSP-based design reduces internal component count and allows for better control of electrical ripple and noise. "

This particular power supply offers 125amps at 12v on a single rail. Apparently, it can be split up through software to split power across its outputs.

In theory then, when used in union with a series of boost convertors to split up the 125amps, wouldn't this type of constant voltage power supply be suitable to distribute power across a huge amount of COB led's?

I hope I'm not high jacking this thread with all of this. It seems relative to the idea of using an alternative power source opposed to the standard Meanwell lot.

[MoosingAround]

My electrical knowledge is limited, just a hobbyist, but if you're comfortable with using a multimeter and you're willing to risk a LED strip, go for it. My only experience with repurposing a desktop computer power supply, I only wanted the 5v rail (maybe it was 3v3), and it wasn't happy without draw on the other rails as well. Required a minimum load to run smoothly.

What you need to be aware of though is that LEDs will draw as much power as possible until they pop, unless physically limited. I'd have no problem plugging specific flexible LED strips (with that 3m tape on the back) into a re-purposed power supply, because they have resistors every 3 or so diodes to limit the current. They're meant to be used with generic cheapy power supplies.

These rigid LED strips (samsungs / bridgelux) are just a Series+Parallel combination of diodes, no resistors. The BXEB gen2s will draw an extra ~50% current if you raise the voltage by 0.5v. What that relationship will do partnered with a generic cheapy power supply that might have fluctuating voltage? I dont know. Id at least want a fuse on there to blow if things snowball out of control.

Boost Converters are going to contribute to inefficiency, but if you're recycling parts at home, electrical efficiency isnt your number 1 priority. Stepping up 12v to 48v for cobs sounds inefficient to me, but we've reached a point thats over my head.

[electrok-d]

Thank you for your thoughtful response. I too have limited electronics knowledge, but have been a dabbler in the craft since my youth. I can wire basic household applications, read an electrical schematic, and operate all functions of a general multimeter. It's a start

I was under the impression that an electronic device would only accept as much current as it was designed to employ. I could be wrong, but perhaps you are referring to thermal runaway with regard to heat and voltage? In the case of using a boost converter, if it is of decent quality, it can also act as a voltage/current regulator. Bvolt's link to the buck convertor is on the right track for what I'm shooting for. I found one that controls constant current and constant voltage, has presets, and handles 15 amps for about $46. Check this out:

https://www.amazon.com/DROK-Numerical-A ... erter&th=1

In the case of voltage variance and the potential for wavering amperage, a high quality computer power supply also has built in controls for this. Here is an excerpt for a Corsair power supply that would potentially supply 83 amps, has software control features, and costs $230:

"Over-voltage protection, under-voltage protection, and short circuit protection, over power protection, over temperature protection provide maximum safety to your critical system components."

So on its face, it seems to me that a decent computer power supply that includes internal voltage regulation in combination with a series buck converters that also allows control of voltage/current should provide way more power than a typical led driver on the market and allow for future lighting expansion. For about $460 you'd have variable voltage and up to 75-83 amps to work with (depending on the number of buck converters in use).

I think I'll start by buying 4 cob leds and the buck converter I listed above with a 500 watt power supply I have laying around. For the experiment, I'll be running the LED's at least 25% under power and with CPU fan/heatsink hack. I should be able to run the fans off of the existing power supply. This seems like a relatively cheap experiment. I'll report back here once everything arrives and has been set up.