Pneumatics Rookie Problem

Okay, I’ve searched on the forums for the answer to my question but either it’s not there or I’m using the wrong search terms.

Regardless, what I need to know is how to get this setup to work if possible:

4 accumulators at 120 PSI
4 2" Bore 12" Stroke cylinders at 60 PSI
Compressor (maybe)

How do I hook up the solenoids so that the cylinders are not pressurized until I want them to extend? ie, there should be roughly the same amount of air in the tanks as is needed to fill the cylinders (2" x 6" at 120 PSI vs 2" x 12" at 60 PSI), so what kind of solenoids and linkups would I need to transfer the air? The cylinders only need to be extended once but then they need to stay there at the end of the match.

Thanks muchly for any assistance

EDIT: I just realized, that with the fact that air wants to equalize pressure, that opening up the accumulators to the cylinders will only result in them being pressurized to 30 PSI. What I need to know now then is how much force the cylinders put out at half pressure, and how fast the compressor could put in enough air to bring the cylinders to 60 PSI.

Pneumatic hook-up: you need to put the supply pressure (from the accumulators and compressor) to the common port of the Solonoid valve. You will want to block the normally open port so you dont dump your air out to atmosphere. Connect your cylindar to the normally closed port (if you want to keep the cylindar extended at the end of the match then block the dump port to the normally closed side, however doing this will not allow the cylindar to retract during the match).

Electronic setup: hook the solonoid (the electrical part of the valve) to a spike and control the spike from a digital out on the RC. Control the digital out via software. If you want to fire all cylindars at the same time then the solonoid valves may all be hooked to the same spike.

A 2" cylindar has roughly a push factor of 3 (given friction … et al.) Thus 30 PSI will give you 90 pounds pushing force (for each cylindar).

*note that if the 4 cylindars are not near each other then they will extend at different speeds (as the air equilizes) with an offset load. In addition if this is at the end of the match (when the compressor shuts off) they may not fully extend (as pressure equalizes) to the same length if the load is not evenly divided.

The 2007 Pneumatics Manual has all of your questions answered.

One small correction: Spikes should be plugged into the RELAY outputs, not digital inputs / outputs. The relay outputs can be reversed to reverse the spike, which actually allows it to control two solenoid valves. See the best practices document and the pneumatics manual.

relay1_fwd = 1; // turn on + side of spike
relay1_rev = 1; // turn on - side of spike

By wiring one solenoid to each side of the spike and the common of the solenoid to ground at the breaker panel, you can control both independently.

Brian

Thank you for your responses, this makes it much clearer to me what I have to do.