Air compression modulation

[bmarick]

hey does anyone know if you can adjust the spike relay so it allows air in at a changing rate like the value of an X squared on the values of 0 to 5?

[RyanN]

First of all, the Spike Relay module does not control the air flow. It would be a pneumatic solenoid that controls air flow. Second, we don't get any type of solenoids that would allow you to change the rate of air flow.

Probably the best way I can think of doing this is to put a servo on one of the hand operated release valves. Even then, I'm not sure if the servo will be powerful enough to turn the valve. You may want to use a globe motor plus a potentiometer to turn the valve.

I'm not sure of the FIRST rules on this as you are using KOP parts to do this, and as long as you don't alter the valve, I think it would be legal, but don't quote me on this.

Remember, you are still required to have a manual release valve.

As for how to control direction, put the "custom" valve on the inlet of the solenoid, then control direction using the solenoid.

Hopefully this all makes sense, and if needed, I can try to draw a picture of what I have in mind.

[EricVanWyk]

You can attempt to duty cycle modulate the solenoid. Unfortunately, you might break it, and your resolution would be horrible.

Turn the solenoid on and off very quickly, and you might be able to get a quasi-open state. In an ideal world, if you blink the solenoid once per cycle, you would get half the air through-put.

For a slew of reasons, this won't happen perfectly. For one, you need to toggle it very quickly. Neither the spike nor the solenoid are rated for this.

That being said, I have seen it done and I have done similar things on different hardware. If all you need to do is slow it down, go for it. Just keep spare parts on hand.

[DonRotolo]

What, exactly, are you trying to accomplish? Maybe there's another way?

[bmarick]

the idea came up in a intro to robotics class I'm teaching with my robotics team, we noticed a lot of the energy was being lost due to the fact that the compressed air flowing into the cilindar was at a constant rate, causing rotary movement of the cilindar and other forces. if you could start out gradually but then increase the air flow into the piston then you should be able to increase the pressure over time so that the vibration and rotary movement is minimized right?

[vivek16]

Put a motor with a multi turn pot onto one of these. You already got 6 in the kit this year.

That should work with some tweaking right?

-Vivek

EDIT: you would have to put a brass connector and a straight connector on there as well but it should work.

[DonRotolo]

Originally Posted by bmarick

you could start out gradually but then increase the air flow into the piston then you should be able to increase the pressure over time so that the vibration and rotary movement is minimized right?

Maybe, maybe not.

The rotation of the piston is not a result of fast air entry, at least that's not a major factor. The kind of load on the piston rod is the bigger factor. Vibration or jerkiness is a result of fast air flow, but maybe just reducing the inflow rate to a smaller, but fixed, value may do it. The flow control valve Vivek cites is the way to do that.

An alternative - perhaps for an experiment to see if what you're thinking really works or not - would be to get a number of solenoid valves (say six), each has one side connected to the air source, the other side through a flow control valve to the cylinder. Set the first flow control valve for a small airflow, the next more, and so on, until the sixth one which has no flow control valve atall (fastest).
Then, turn them on one at a time, but as fast as you want, like valve 1 then wait 0.1 second then valve 2, and so on. Longer delays (like 0.25 second) should be tried to see their effect.

When you figure out what happens, be sure to tell the rest of us, thanks.

Don