This graph is showing voltage and current for a recently built Version 7 microscope with a Raspberry Pi 4 with 4Gb RAM, a Raspberry Pi 4 power supply and a new Sangaboard V 0.5.4. You can see two cycles of power on, booting, stable after boot finishes, individually move X,Y, and Z, home X,Y,Z all at once, and power off.
In this test, voltage at the Sangaboard input never drops below 5.1 Volts and the current never exceeds 1.25 Amps.
Thanks for posting this, it’s really nice to see! Power issues have been intermittent and annoying for most of the development of the microscope, mostly resolving with the switch to Sangaboard 5, Pi 4, and USB-C power. I’ve never properly measured the voltage/current, so it’s really nice to have your plot. Out of curiosity, do you have a neat test jig of some sort to make those measurements?
Hi! I am using a Fnirsi FNB-58 USB test device with an app on either a PC or an Android device. https://www.fnirsi.com/products/fnb58 Also available from Amazon. This is a super useful device for making USB voltage and power measurements. It’s so sensitive you can see current drawn by WiFi radios turning on and off in microcontrollers. You can go deep in understanding USB protocols too, especially the newer PD (Power Delivery) protocol which I think the Raspberry Pi 5 power supply uses.
Thanks! I think Pi 5 does use PD, but it’s non-standard (they use a high current 5V mode) which is a bit annoying. I think the Pi 4 is probably still the best option for the microscope for now - I guess we’ll need to pay attention to that in the future, though!
It is great that you’ve confirmed we don’t overload things with the motors - while we were pretty sure it was OK, it’s nice to confirm it. It would be interesting to see what it looks like running off a power bank - though of course they are all slightly different…
