Buck Converter to Power Crypto Mining?

[hwy17]

I just tried a regular ATX PC and it did not work. It gently sparks as it takes up the 48v but particularly the green light on this PC's power supply does not come on like it does for mains voltage. Possibly there is a protection mechanism that qualifies the input voltage as adequate before accepting it, to protect against the over amperage condition I mentioned above.

 

[BradCagle]

I don't think transformer is exactly the right terminology. I'm no EE but as I understand it it's a switching regulator it takes any higher DC voltage and switch it down as

Switching PSU's use a High Frequency transformer. It rectifies the AC to DC, then switches that DC at high frequency though a transformer, and then rectifies that again.

required, and that's what gives it the regular ability to accept 150-350VDC from worldwide mains.

The Switching frequency is what allows it to accept different voltages. There's a feedback loop from the output of the HF Transformer back to the switching MOSFET, the pwm signal gets changed based on this feedback.

I've just tried it with a 12v adapter like this and it powered up a micro form factor PC like you'd use for a firewall off 48v:

https://imgur.com/HKRfDWY

I will try a full ATX PC next.

OK, then It's possible the little switching power adapter you have is using a half wave rectifier, that would put you closer to the 48v range

 

[BradCagle]

I just tried a regular ATX PC and it did not work. It gently sparks as it takes up the 48v but particularly the green light on this PC's power supply does not come on like it does for mains voltage. Possibly there is a protection mechanism that qualifies the input voltage as adequate before accepting it, to protect against the over amperage condition I mentioned above.

Probably using a bridge rectifier which would put the voltage requirements much higher than 48v

You might be able to find a PC PSU that uses a half wave rectifier, if you can, I think that would work at 48v

 

[BradCagle]

BTW I know it's confusing but these things still use transformers. They are much smaller than what we use to see back in the day. Hi Frequency switching is what allows this reduction in size, and a massive cost reduction.

Basically the old school big transformers ran at 60hz same as your AC power, now they run at 20khz-2Mhz, this allows things to get tiny. The voltage regulation is also a function of the switching (and feedback loop).

Back in the day it was big transformer with hot linear regulators.

 

[hwy17]

Ok, why do you think it is that it will accept 150-350 rectified but not 48 then? Protection mechanism?

It seems like it has the necessary magic to make 48 into 12DC.

 

[BradCagle]

Ok, why do you think it is that it will accept 150-350 rectified but not 48 then? Protection mechanism?

It seems like it has the necessary magic to make 48 into 12DC.

Probably yes protection logic (AC Power not in spec dont try to run). Also might be specs of the HF transformer.

 

[BenQ]

I have them set to pull 100w each, and then the mobo pulls something like 20-30w. I have 3 more A4000's to put in there.

This is the converter I'm using in the shed. It has no voltage drop, and it rock solid https://www.mouser.com/ProductDetail/826-ADQ800-48S12B-4L

But you do have to build a board for it since its a module. I like these isolated DC/DC converters because there's minimal chance they could pass the higher (48v) through to the GPU's


BTW, I have 3 1660 supers. I'm going to put them on a board with that 24v-12v DC/DC (the one I added a cap to). I'll let you know if it works,

Thanks buddy! Yeah that converter looks rock solid! Mine on the other hand is sagging by 0.7 volts (12.4v) when putting out 6 amps lol that’s about 75 watts…if I try to put my 1660 on there and it pulls 56 watts I imagine it drops another 0.3-0.5 volts (11.8 or 11.9v) which might make the gpu throw the malfunction I’ve been getting.

 

[BenQ]

Haha, thats what the name is from. Been called Lt.Dan ever since the movie came out.

The cost of extra parts and stuff was what put me off, capacitors or high dollar converters wasn't worth the few percent in savings of efficiency. Not to mention Server PSU's are cheap to replace, and I can easily keep spares on hand. My rigs are also in a Shed, 150ft from my battery bank now, so the distance would kill it.

Just for numbers, I have 1 rig that pulls 488w, 8 GPU's. Its running server PSU's at 94% efficiency, so from the wall 519w. Then its being inverted from my Sol-Ark from 48v to 240 at ~95-96%, say 94% to be generous. A total of 552w being pulled from the battery to power these 8 GPUS. A loss of 64w total. Not the end of the world, and reality its probably less.

I just finished putting this rig together; 1x 3080 and 7x 3060's. Running off 2x 1400w PSUs. I make these cases at work and put together the rigs myself.
View attachment 148456

That’s awesome! I saw you had a post about putting air conditioning to keep your batteries and inverter cool in the summer, what do you use to keep the miners cool? 64 watts could be another 1660 super for me lol, but when you’re running 3060’s that’s pretty negligible. As you said you’re not keeping them in the same location as the batteries either so a longer AC run is more practical anyways.

 

[Lt.Dan]

That’s awesome! I saw you had a post about putting air conditioning to keep your batteries and inverter cool in the summer, what do you use to keep the miners cool? 64 watts could be another 1660 super for me lol, but when you’re running 3060’s that’s pretty negligible. As you said you’re not keeping them in the same location as the batteries either so a longer AC run is more practical anyways.

No air conditioning/cooling for the miners. Airflow is the only thing you should use. Even with 110*F ambient, with proper airflow, the GPUs will stay manageable.

 

[BenQ]

Caution if you have OCD do not scrutinize my temporary set up too closely. Suffice it to say that my 360 watt 48v to 12v Dc-Dc converter only supplies around 100 watts continuously. Any amount over that creates way too much voltage drop and my PC and GPUs crash. So, I took the battery I got for free from @Will Prowse and repurposed it to stabilize the voltage of my converter and now my DIY mining rig (1 CPU & 1 GPU) is running 24/7 off of DC