I had constructed my MMDVM DMR hot-spot using a Raspberry Pi 3 because the received wisdon was that putting the MMDVM hat on a Raspberry Pi 4 would cause it to overheat. My problem was that I found the web interface to be a little slow for my liking. It was usable, I just would rather it were more responsive.
So I set out on a search to find a way to use the MMVDM hat on a Raspberry Pi 4 and provide proper cooling. The solution was found in the Argon Fan Hat. The key feature that allowed this fan hat to work was that it passed the GPIO connector through to allow for the MMDVM hat to sit on top of it.
That, coupled with a Raspberry Pi stand-off salad allowed me to make a triple-decker sandwich. Left to right in the picture below we have:
- Raspberry Pi 4B
- Argon fan hat (plugs into GPIO header and passes it through to the next layer above)
- MMDVM dual hat (plugs into the GPIO header passed through the Argon fan hat)
By using a Raspberry Pi hardware salad and selecting the right combinations nuts and stand-offs between the sandwich layers it all went together nicely. One thing to watch out for if you do this: I had to remove one of the bolts and nuts that attach the fan to the fan hat PCB. this was because it interfered with the CPU heat sink on the Raspberry Pi and wanted to unseat it.
The Argon fan hat is here:
The fan installs some software packages to do it’s thing. They don’t seem to conflict with any of the WPSD software packages that run the hot-spot. There is a configuration utility that allows you to configure the fan behaviour from on all the time to various speeds at various CPU temperatures.
Testing is in progress but initial impressions are good. The WPSD web interface is much more responsive using the Raspberry Pi 4B than it was on the 3B. I have the Argon fan set to run at 30% speed all of the time and it is maintaining a CPU temperature of 35C which is excellent.
While the fan is not overly noisy at 30% speed, my intolerance of fan noise in the ham shack means that my DMR hot-spot has been relocated to my Harry Potter data centre under the stairs along with the rest of the IT infrastructure.
I am very pleased with the overall results of this configuration.