One of the several challenges home miners face is that most of the mining equipment require 240v power. Most houses in the United States have a few 240v outlets at their electric range and clothes dryer, but it really isn’t feasible to unplug those appliances for a miner. Upgrading electrical infrastructure is prohibitive due to cost. Another issue is that the miners are locked to use only their stock power supplies. Try to plug in an alternate power supply and it won’t hash. Zack Bombsta from Pivotal Pleb Tech has been working on these problems and has solutions. https://pivotalpleb.com/
Zack figured out how to pair a 120v power supply to a newer generation single hash board. He’s created a printed circuit board that basically jailbreaks the hash board to accept any power supply. Using an APW3++ power supply from an older generation Antminer, you can mine bitcoin on 120v power with Pivotal Pleb Tech’s “Loki Board.”
The hash board donor machine I used is an Antminer S19 jPro 92Th. This particular machine has a stock efficiency of 29.5 joules/Th. The reason for only running one hash board is that in stock configuration with three hash boards, the S19 jPro uses around 2.7kW. This amount of power exceeds what a standard home 120v outlet can handle. Most 120v outlets are on a 15amp circuit. 2.7kW would require over 22amps.
The donor machine is running at home on 240v minus the one hash board for this single board build. I wanted to be able to continue to utilize the rest of that machine. So it is currently hashing with 2/3 board with a piece of high density styrofoam in the place of the missing hash board.
The APW3++ power supply is from an older generation S9 Antminer is readily available and cheap. It can run 1,100 watts which will power the single hash board from the S19jPro safely on 120v power outlet in your home.
Zack had shared the proof of concept, and he also shared a modification to the APW3++ power supply to up the DC voltage output allowing you overclock the single hash board. I wanted to build one of these, but begin testing a different way to assemble the single board 120v miner.
I had some ideas about how to put this together. We must have all the miner components, hash board, power supply, control board, and fans. I work in construction, and we frequently use slotted channel called unistrut. It just happens that the height of the unistrut is 1-13/16”. This is about 1⁄4” greater than the thickness of the hash board. The other thing I wanted to do is use plexiglass so you could see the hash board. Two reasons for this. One, you can see if the heat sinks are getting dirty and two, I just think it is cool to see the guts of the electronics. So sandwiched between two pieces of plexiglass, stood up with the unistrut channel I have housed the hash board.
The control board is placed near to the connections on the hash board because it has to be. The ribbon cable that connects to the hash board is short. The control board is mounted on small screws that thread directly into the plexiglass. In retrospect, I would rotate the control board 90 degrees so that the ribbon cable connection isn’t pulled so tight.
For an easy fan solution, I started using the leftover stock Antminer fans I had on hand. With the plexiglass staggered front to back just the right amount, I was able to make the 120mm fans work with them tilted on the inlet and outlets. Maybe not the most efficient way to do it, but at this point, I just wanted to see if it would work.
I decided to mount the power supply on the back of the unit. I drilled a few holes in the bottom of the PSU case and drilled and tapped the plexiglass to mount it. The power cables from the PSU to the hash board need to be heavy gauge. The stock configuration of the S19 jPro uses bus bars. With the APW3++ at 12.25v at 1,100 watts, that would be roughly 90amps.
Heavy gauge wires are required. I cut a couple small chunks of welding lead off the ground cable on my welder in the garage. I believe these are 2AWG. One thing to note is that the positive cable (yellow wires on the PSU attach to the end lug on the hash board closest to the end of the board. Don’t hook up your power with reverse polarity. To make it work, I had to modify the PSU case some to allow for the heavier lugs I used.
Zack has a hack to up the voltage output of the APW3++. He’s the expert on some of these numbers, but the jPro hash board prefers a higher voltage than the APW3++ stock 12.15v. There is a small potentiometer that can be removed and replaced with a fixed resistor which will change the output voltage. Depending on what resistance you install you can fine tune the output voltage. I opted for a 2,700 ohm resistor which would allow me to overclock and produce more hashes. The result of the upgrade changed the voltage from 12.15v to 13.25v. I was looking for a balance that would allow me to over clock but not red line the PSU. You can find Zack’s guide for the PSU modification here.
The control board is a Xilinx C71 running BraiinsOS firmware. Not too much to say about the control board, but there are some differences between them. It’s important to note that each control board may require a unique Loki board configuration.
My initial results surprised me. I was
expecting a drop in efficiency since thisvis a Frankenstein machine. This single board from the 92Th machine makes 37Th by itself. Drawing 9.26amps at 119v equals 1,102 watts. 1,102 watts/37Th = 29.78joules/Th. So stock efficiency but producing about 20% more hashes! It’s like the 92Th machine running at 111Th. So not only can we run on 120v power, we have upgraded the performance significantly.
Once it was up and running. I found the stock fans to be too loud. I wanted to improve the cooling efficiency and slow the fan speed down some. The initial design left a gap on each side of the hash board for air to circumvent running over the heat sinks. I installed some high density styrofoam in those gaps and found that the fans ran about 15% slower.
Still looking to do better yet, I installed an AC Infinity 6” inline fan with a galvanized duct from the local home store to replace the
stock fans. This further reduced the noise. I was able to rework the unistrut and moved the angle brackets forward that hold the uprights for the hash board. Then prepossessing two of the brackets, was able to mount the AC Infinity fan to one of the legs of the assembly.
The other thing to add with the AC Infinity fan is Zack’s Cloudline Njord board. It plugs directly into the control board and controls the speed of the AC Infinity fan. I’m currently using these on most of my Antminers at home to improve cooling and reduce noise.
Check out my video here that shows the install of the Cloudline Njord Board: https://rumble.com/v2l9sym-bitcoin-home-mining-upgrade-your- miners.html
A Wifi bridge was added to remove the need to run an ethernet cable to the control board. I didn’t realize how much I’d appreciate not having to run an ethernet cable. You need to plug it in initially and connect to it to set up the local wifi networks you want it to talk to. The Vonets device I’m using can be found on Amazon for about $25. The nice thing about this device is that it runs on 5v-15v so you can hard wire it directly to the PSU. I cut the power plug off and tied the wires right onto the PSU lugs. I liked this thing so much I added one to my S9 space heater as well.
The next step is to further improve the hash board housing and assembly. In my opinion there is too big of a gap between the end of the heat sinks and the plexiglass. In order to force the air through the heat sinks, the gap should be as near to zero as possible. Maybe .010”.
While some of the component prices may vary greatly on market conditions, here is a quick price list rundown…
$300 1/3 of a used Antminer S19 jPro
$40 APW3++ PSU
$130 Xilinx control board
Then if you want the fan upgade you have:
$120 AC Infinity 6” Inline Fan
$45 Cloudline Njord Board
Here you have around $500 in items needed, but maybe you have a stash of decommissioned S9’s in the basement and a broken S19 you can salvage a hashboard and control board from. Then you need the hardware to assemble a framework to hold it all. There are some other designs out there. @satstackingpleb on twitter has a build using an electronics cabinet. I like the simplicity of that, and it keeps everything contained a little nicer. My next iteration of this may utilize a cabinet like his.
An easy to assemble, efficient, 120v powered, reasonably quiet, Bitcoin miner deployed in a way to recover the waste heat will be sought after by everyone regardless of how you value Bitcoin. I hope this experiment will help more people realize the potential Bitcoin home mining offers.
If this project interests you, please feel free to send feedback, criticisms, hate mail, suggestions, whatever.
If what you found here was helpful and want to leave a tip, you can zap me on Nostr or send to my paynym.
Travis Bitckle @bitckle