Regulators typically aren't designed to sink current, but to source it. The 5V buck regulators on our PSU boards won't work as sinks so getting 7V across the 12-5 on them doesn't work. An actual high-current rail on a PSU is probably more readily able to work with sinking currents, especially if the current is quite a bit lower than what it's capable of handling in output. It kinda depends on the topology of the regulator. I wouldn't trust most things to handle reverse currents near high enough to power an S5, even at 9V loads.
I've thought about doing the 36V chain also, but I don't have any string miners to test with. Four boards on a Prisma would do it, except you'd need level shifters for the serial lines, which could be problematic. S5 there's no trouble stacking, since the only IO is ethernet, which is an isolated line independent of local ground references. You couldn't put two boards of an S5 in series on the same controller without smoking the controller, but four whole machines should work fine.
We're working on a prototype regulator for adjusting voltages for string miners; hopefully we have some good numbers in the next week or two.
looking forward to results on that.
BTW this tiny little piece of gear I purchased on amazon is a very nice fan controller.
If I choose to lower freq to 300 and volts to 8> I would have a very quiet s-5 under 50 db running cool.
I figure this small dc to dc converter can run 6 stock s-5 fans.
Just to be clear Phillip, are you only applying the voltage regulator to the single stock S5 fan? This essentially removes the S5's control of fan speed and turns it into a manual setting on the voltage regulator? Any other fan changes involved?
Thanks for your exploration of this area.
yes but that controller can do about 6 fans. feed it 12 volts from your psu. I used the 4 pin molex cable. my molex wires can do 75 to 100 watts on the evga 1300 g2
basically slowing the stock fan to 5-10 volts allows a 1 at a time adjustment. it stays at the volts you pick. if 10 volts is too loud try 9.5 or 9 or 8. there is a small screw to adjust the volts with a flat blade tiny screwdriver..
you need to think of it as a manual fan control. what is nice is it is cheap and can handle a lot of fans.
I am getting bearable sound levels and 383 freq.
if you want really quiet feed it 5 volts and freq 275.
