For those of us that are having at the heart of our astronomical setup a RaspberryPi it has been for long now an idea to be able to centralize some critical monitoring and control functionality rather than having extra boards and equipment around. Power boxes are great, and they come in various flavors from many companies on the market. Unfortunately they are either lacking functionality, are expensive for what they are or simply are not open source enough for my taste. That's why I decided to spend some time and design a RaspeberryPi 4 compatible hat that includes the following functionality:
4x 12V switchable outputs @3A each
2x 12V PWM switchable outputs @3A each
1 adjustable 6-12 V output @3A
Current and fault monitoring for each channel individually
Temperature, Humidity and Pressure sensor port (for an external readily available module)
Automotive grade electronics and design (to ensure reliability on all environments
Everything seems to fit nicely on a RPi hat form factor. Attached are some renderings of the design so far.
I designed everything on KiCad and the board designs are released as open source hardware (CERN-OHL) at this repository: gitlab.com/pierros/astrohat
I am posting this here with the intention to solicit feedback and potential contributions to my effort.
The design can be considered complete for v1.0 and I plan to order some boards soon for testing and software development. I envision a daemon running locally on the RPi and an indi driver to communicate with it.
How does the feature set seem to people? Anything obvious missing?
Would people be interested in a small production run?
Once the first boards arrive and I can verify functionality and placement of ports, I plan to also design a case (probably an aluminum enclosure for the Hat together with the RPi).
Any ideas, feedback, comments are highly welcome!
ps. as a side note, I would really like to see more open hardware projects in the domain of astronomy (amateur or not) and see a flourishing community around them.
Excellent project, and I am sure there will be many takers of these, I would be very interested in one...unfortunately I am not a skilled electrician or coder so can’t help much with the design...but you seem to have that all sorted anyway..
The channels in pairs can draw 6A combined. Which means that in theory you could get e.g 5A in Channel A and then 1A in Channel B and still be OK. I guess we will have to make this somehow visible on the interface too (and on the case?)
I was wondering if something was available the other night as I came inside with my arms full of wires, cables, and power adapters for the various bits and pieces attached to my scope. Good luck on this!
Actually I think you have covered pretty much all of what is sneezed on a typical imaging set up, and what you would get on a commercial power hub, apart from maybe an output for a motor focuser..but with the units around now that have the controller built in to the motor housing, it’s probably not needed....
So all good, I would certainly buy one if you produced a few, along with a case for the lot...
Oh this is promising. A dedicated astronomy HAT. Love it.
I ended up cramming GPS, RTC, Motor controller and a power supply board (Docker Pi) within my case. So if there is anything worth adding, I would say GPS, RTC and 5V@4A power to the Pi is what's most useful.
For motor control I installed the Adafruit motor HAT. But the Pololu A4988 controller is arguably better with higher supported PWM frequencies.
I just pushed a new version on the repository and added the following:
- An external TTL connector for connecting a GPS module
- A RTC complete with battery
(here is a pic with the connector and the RTC)
As for the rpi supply the board has a 5V@3A power supply integrated.
Motor control is a bit of an overkill at this point imho, mainly because most of the newer focusers have the control integrated, but please let me know if you feel this is a showstopper.
@AstroNerd: regarding cooling, indeed it will be an issue. we will have to see once the first dev board arrives how we can accommodate a fan or a heatsink.
Motor control is by no means a show stopper and certainly exceedingly difficult to include, that's why I didn't list it among the most useful features. However spare 5V and 12V headers with reasonable amperage supply and some filtering to power a stepper motor board one might add would be appreciated. I had to use a mini-buck converter stuck beneath the power board to power mine, (Follow the white power wires in my previous image).
As for anything else. Maybe an on/off switch. For cooling the Pi4, a 30mm fan is quite adequate in my experience, but I also have heat sinks installed. Regrettably it would monopolize a lot of space. As for GPS I am not very familiar with the TTL drone modules, are there options available that allow for an external antenna? I highly recommend supporting modules with a uFL socket for external antennas.