Hey Skot! I came up with a similar idea at the start of the year and had PCBs manufactured, but only recently got around to putting them together.
Compared to your design, it's a complete breakout board that provides access to all pins in 0.1" format, as I thought better having too many broken out pins than too few.
Anyhow; you beat me to uploading the whole thing and testing it out. Good job; I read that it's already working quite well, so far.
However I'm wondering what you use to supply the 0.8V at probably around 10A that those 2 chips should be pulling. My next step would have been to design a buck converter circuit. Do you just use a lab bench power supply?
I'm definitely interested in collaborating to maybe make this into a compact USB miner with integrated FTDI chip and buck converter (I have a lot of unused slots in my GekkoScience USB hub..
).
Otherwise, I can see a pod miner with more than 2 chips being interesting, too, maybe targeting 95W so a standard quiet CPU heatsink could be used.
Disclaimer: I'm a big fan of sidehack's work / GekkoScience and don't think such an open source project is going to compete with them. For one, their flagship Compac F is much more efficient and much faster, and also it's a ready-to-go product. These are PCB files that users have to get produced themselves and get to work soldering them, too.
Hey n0nce!
that PCB looks good! it's cool to see more people doing this. Were you able to get the BM1387 pin pitch right?
Thanks; it should also allow to mount a heatsink with thermal cement or adhesive thermal pads, if the pin headers are soldered on the bottom (or the heatsink fits in between them). I just thought for early tests like figuring out the pinout and which passive components to connect where, even a piece of copper clamped to it should suffice.
I did consider adding holes for a northbridge heatsink like you, though!
Regarding the pitch; I actually found a BM1387 footprint / component in
https://easyeda.com/editor and crossed my fingers that it's correct (it is).
For now I have just been using a cheapo adjustable power supply from Amazon. You're right, an onboard buck converter is the way to go. Unfortunately they're a little hard to come by these days with the chip shortage. I did a test with the MAX20499 (
https://github.com/skot/MAX20499_breakout) but then I realized Maxim won't give the full datasheet to plebs. Still looking for a better part. the TPS51219 on the Newpac is completely out of stock.
You mean a lab bench power supply or a random prebuilt buck converter? And just to clarify: you do have 1.8V regulators on-board, too, right?
As for the main step-down regulator, I actually envisioned building my own synchronous buck converter using a buck controller and two MOSFETS, just like GekkoScience.
As you noticed, GekkoScience / sidehack, uses a
https://www.ti.com/product/TPS51219, which is a
buck controller. It just controls two MOSFETS in a synchronous buck converter configuration, like this. The MOSFETS are in place of the switches and the controller is not shown here; it controls the timing to achieve the right output voltage.
Yup, he uses a synchronous buck controller IC together with 2 mosfets.
Looks something like this. They are switched on and off by the controller, which creates accurate timings to achieve the required duty cycle and thus output voltage.
I don't think that
integrated (single chip) buck converters exist with the types of power we need to push and the efficiency required. For instance, a linear regulator going from 5V, 3A to 0.5V, 30A would go up in smoke immediately.
I want to experiment with offloading everything that cgminer does (fetching work via stratum and rolling the extranonce) to an onboard microcontroller in a pod miner setup. I've started with an ESP32 so I can connect over WiFi too. (
https://github.com/skot/bitaxe/tree/pro). Pair that all with a power supply suitable for solar and you could just litter your roof with these things
That sounds like a cool idea, hadn't thought of that! Making a more standalone, pod-format device sounds great to me. I'd just personally focus more on the power supply first and getting my breakout running; feel free to work on the ESP stuff - then we can merge everything.
Is there a "standard" CPU heatsink with fan? I looked around at these but couldn't really come up with anything. It seems like the economies of scale with the whole PC water-cooling scene could be useful here.
Well I meant standard in the sense of 'Intel LGA 1151' or 'AMD AM4' - if we replicate their hole spacing and copper area, it would be possible to just take a box-standard thing like this:
https://www.newegg.com/rosewill-rocc-16003/p/N82E16835200114They can easily cool 100W, only downside is pretty small copper area. So the ASICs will need to be very close and amount of chips per cooler would be space-limited.
