[Nut-upsuser] Supporting a DIY UPS with minimal effort but maximum gain

[Kelly Byrd]

I put together my own DIY UPS,  it's a RV charger/converter, an inverter,
and some batteries. I use an Arduino and the HIDPowerDevice library (
https://github.com/abratchik/HIDPowerDevice) to get it to talk to NUT. Been
working great for months!

The Arduino is connected to two modules:
* AC detection circuit to measure mains power on/off
* Voltage divider and an external ADC to get a reasonably good DC voltage
level for the battery which I turn into the a charge percentage.

This uses the USBHID driver in NUT and "just works" as long as you're using
NUT 2.8.2 or later. I used the example code in the HIDPowerDevice library
as a starting point for running on my Arduino.

I can share more specifics about the Arduino side of things off list if you
want, the NUT side of things is pretty boring and normal.

On Wed, May 15, 2024 at 3:27 PM Kiril Zyapkov via Nut-upsuser <
nut-upsuser at alioth-lists.debian.net> wrote:

> Hello,
>
> I found out about NUT just days ago while searching for a solution for my
> home setup. After some digging through the interwebs, I come to you with
> questions.
>
> I'm putting together a DIY 12V UPS, very similar to what this guy did:
>
> [1]
> https://baldpenguin.blogspot.com/2015/10/diy-12v-ups-for-home-network-equipment.html
>
> The objective is to keep a bunch of mini PCs and network gear online for
> as long as the battery lasts and then provide a mechanism for a graceful
> shutdown of my NAS and other appliances for which cutting power would not
> be healthy. The project above is missing the "connected" part. I want to
> get mine to play with NUT nicely. Other prior art is this project:
>
> [2] https://github.com/xm381/Raspberry-Pi-UPS
>
> Mentioned in a previous thread here:
>
> [3]
> https://alioth-lists.debian.net/pipermail/nut-upsuser/2018-August/011198.html
>
> A valid approach -- emulates an existing protocol on an arduino.
>
> Are there other similar projects that you know of? I found plenty of "DIY
> UPS" projects, but none were "smart".
>
> I am able to put together firmware for some micro which will take care of
> measuring voltages, currents, possibly also turn on/off loads, serial or
> USB or IP are options. Not sure yet what hardware features I'll put
> together, but this depends somewhat on the approach for getting this thing
> integrated with NUT. PSUs and batteries are already on the way, and my junk
> drawers have most other parts I may need.
>
> So, options found so far:
>
> * Use genericups. Least favorite option, very limited features
>
> * Use the same approach as [2]. If I were to go that route -- which is the
> best protocol to pick for emulation? I'm looking for something simple,
> extensible/flexible and well-documented.
>
> But what I really wish was possible was the ability to describe my device
> in some format, feed it to a generic driver in NUT and profit. I see some
> efforts have been made in this direction, most notably:
>
> [4] https://github.com/networkupstools/nut/wiki/Data-Mapping-File-(DMF)
>
> What is the state there? Is it usable for USB HID? Or, how hard would it
> be to make it usable? Even a modbus description will do -- implementing the
> modbus server (yes, server, I'm being politically-correct) over serial or
> even TCP is easy, if only there was a way to dump a CSV with register
> descriptions in some magical driver...
>
> And yet another approach which comes to mind is to implement my driver as
> an external executable. This may be completely unfeasible and stupid, and
> please let me know if it is. But, from what I gather, drivers run in their
> own process and talk to the daemon via a UNIX socket. Why not make it
> possible for the driver to be just any executable, built/deployed outside
> of the NUT codebase? The socket protocol seems simple enough, and this will
> allow for ... creativity. It could be implemented in any language
> (including scripting languages) and need not depend on anything
> NUT-specific, other than maybe some common CLI interface and/or
> configuration.
>
> I'm hoping the NUT masters will have some insight. Thanks for working on
> this!
>
> Cheers,
> Kiril
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