• aditya mehrotra.

dyno: initial testing, initial problems [udpates]

Finally got around to putting together the Dyno! Here's the setup on the EE-bench in the solar car shop mostly because I'm running out of usable space in my room...



We're powering the SparkMAX motor controllers w/ 24V and the RIO through the DC/DC converter w/ 12V. Initially we turned this system on and put one motor into position-hold mode (just to see if communication was working) and nothing happened.


So it really just wouldn't be proper for everything to work on the first try right?


The error we were getting was the SparkMAXs blinking saying "no control signal found" or "no connection to RIO" while the RIO was on and the lights showed it was enabled. So the problem was not on the RIO code side. It was pointed out to me by a certain Fischer Moseley that the power supply may be an isolated power supply. Rule number one of Electrical Engineering, check your grounds... oops.



So of course we soldered a cable between the grounds of the supply, ran a conductivity check, made sure the outputs were still at the correct voltages and then turned the system on and...


NOTHING!!!!!! YAYY!!!!!!!


So I've emailed support about this issue but in the meantime we're going to grab a second power supply and power the system with two separate power supplies with grounds connected to see if the issue is the voltage, the voltage converters, the ground, etc etc.


BUT GOOD NEWS


Everything works at 12V, and everything works at 14.8V, so we may think of running the whole thing at 16.8V (a 4S LiPo) and put a linear regulator on for the RIO (since it really draws no current at all). But that'll be something to figure out after the whole power supply thing.



OK UPDATE: Now I'm really really confused. So we adjusted the power supply to the lowest voltage level at which the DC/DC converter can still output 12V (in this case this is 18.1V on the supply). Which means the motors are being powered by an 18.1V supply and the RIO is on a 12V supply. Remember if we're still using the DC/DC converter and the converter is the problem, this should not work!



So we turned this on expecting it all to not work and voila... it all works... who knows. So the question now is how far up can we increase the voltage before this does NOT work now that the DC/DC converter is not the issue.



One of the motor controllers works up to 19.4V before it loses signal, the other one works up to like 20V but after 20V both controllers stop responding to the CAN bus... weird. Ok time to email support.


#update #omgrobots #dyno

4 views0 comments
© copyright 2019 | aditya mehrotra