We are trying to control the speed of our pistons as they deploy by reducing the max pressure. We have this code but it won’t work/gives errors.
//Pneumatics
frc::Compressor pcmCompressor{0, frc::PneumaticsModuleType::CTREPCM};
frc::Solenoid IntakeBar{frc::PneumaticsModuleType::CTREPCM, 5};
frc::PneumaticsControlModule PneumaticsControlModule();
PneumaticsControlModule.EnableCompressorAnalog(1, 10);
pcmCompressor.EnableAnalog(1, 10);
double current = pcmCompressor.GetCurrent();
What you’re controlling there is the high-pressure side (before the regulator), while all your solenoids/pneumatic actuators are (or at least should be) on the low-pressure side. What this means is that as long as the high side is above whatever the regulator is set to, you won’t see a change in pressure at the solenoid.
A better option would be to physically change the pressure at the regulator. This can’t be done by software. If you need 2 different working pressures for different systems, you can have multiple regulator, so long as none of them are set above 60psi.
Another option would be to install flow control valves on your actuators. These function by limiting the flow of air into the cylinder, thus slowing the actuation. (Here is an example of what I’m talking about direct from a google search. Disclaimer: I haven’t checked the specs for compliance with the rules, so be sure to do that before purchasing/using anything)
Lowering the total pressure may not help here, depending on your configuration. What you really want are flow control valves. We use them on our intake system and climber pivot arm. You can control both the air flowing out of one side of the cylinder as well as the air flowing in, which can allow you to change the speeds at which your mechanism deploys and stows (to account for gravity, etc).
You can buy flow control valves on McMaster: https://www.mcmaster.com/catalog/128/1162
To reduce the force of a pneumatic cylinder, use a regulator.
to reduce the speed, use a flow control valve (AKA speed control, AKA throttle valve).
A flow control valve reduces speed in one direction. It allows full speed in the other direction. That’s why you typically see 2 of them mounted on a cylinder, or inline from the valve to the cylinder. This gives you controllable speed on extension and retraction.
Scroll down the McMaster page to the “Elbow Control Valves”. These can be used instead of a standard hose fitting and can be adjusted for the reaction you desire.
Also, CTRE PCM doesn’t work with the analog pressure sensor. Do you have such a sensor? How is it wired in? You could read such a sensor hooked to analog input on the RIO and use that to disable the compressor at a lower pressure, but the above answers are probably what you are looking for…
Emphasis mine:
R808 *Working air pressure limit. Working air pressure (air pressure used to actuate devices) on the ROBOT must be no greater than 60 psi (~413 kPa) and must be provided through a single primary adjustable, relieving, pressure regulator.
That is, if you use two or more regulators, all but the primary (highest pressure) must be on the regulated side of that primary regulator.
A prudent clarification, thank you.
Yes, secondary regulator(s) must be in series with the primary, not parallel with it.
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