So this year, our team got some brand new EVO shifters and we want to use them, but we’re planning on going without pneumatics this year, as none of our other systems use them. One proposed idea is electromagnetic solenoids, which can apparently power the cylinder without all the stuff needed to implement pneumatics (compressor, tanks, PCM, etc). Aren’t solenoids already electromagnetic? Has this ever been done previously?
On the semantics of your question:
Pneumatics refer to the compressed air-driven portions of the system. Solenoids refer to a coil of wire that makes something metal move.
It just so happens that Solenoids are used to move valves which direct air in Pneumatic systems. Strictly speaking, your festo (or similar) devices are Solenoid-driven pneumatic valves, which often gets shortened to simply solenoid.
I’m not sure that there are any FRC-legal electric solenoids that would work for shifting. The power limit for solenoid actuators is very low (
only 20W IIRC 10W according to R27), so one might not have enough power to shift gears. Additionally, solenoids in that power range typically a very short throw, and I’m not sure you can find one long enough to fully shift. However, it should be easy to mount an electric solenoid with a 3D printed bracket or something if you were to find a suitable one.
EDIT: I found the exact rule regarding legal electric solenoids:
R27: Electrical solenoid actuators, no greater than 1 in. (nominal) stroke and rated electrical
input power no greater than 10 watts (W) continuous duty at 12 volts (VDC)
The 1" throw would be plenty, but 10W is still quite low for this application.
For an option other than pneumatics… Years ago the allowed servos were not powerful enough to reliably shift the transmission. Since then the rules have allowed much stronger servos. One have them will probably work, but I am unaware of anybody trying them.
Anyone have advice on these 1" stroke electric solenoid actuators? Like, where to buy them, which ones work, which controller to hook them up to? I’ve never used them in FRC and we need them this year, it turns out. I just wanted to piggyback on this topic, it seems many of us might need this info this year.
Don’t know about 1” stroke length, but we use the push-pull and lock style solenoids from Adafruit like this one: https://www.adafruit.com/product/413
Testing last season put the force applied well below what we’d want for shifting. They pull in when current is applied and push out via spring without current.
Lots of ways to control them outlined in the section on electric solenoids in the game manual. We controlled them via the PCM. They don’t work well with side loading, but they’re fun to use in the right application.
Sounds to me like we’re finally going to start useing the word “solenoid” correctly and stop calling (solenoid powered) pneumatic valves the wrong thing.