We have a couple of rookie questions related to our pneumatics system. We are trying to use spikes to control a couple of solenoid valves and we are using LabView.
We have a cylinder that needs to be retracted at the start of the match in order to be within the frame perimeter. At the start of the match we want to push a button to extend the cylinder and it remain there for the remainder of the match. We currently have a single 12 V Festo solenoid for this application.
We have got it working with the spike but it will not stay in place. We can trigger the spike but when we let go of the button it retracts. We think we need to have the button on the joystick programmed as a toggle switch. Does this sound right?
Our concerns are that for this to work correctly the spike will constantly be pulling power which will drain our batteries quicker.
So my questions are:
1.) Is it a good idea to use the spike to be constantly “on” to hold a cylinder in place?
2.) If not what should we do instead?
3.) What is the best way to program a toggle switch in LabView to keep the spike “on”?
Yes, it does. Alternately, if you never need to move the piston during a match, you could begin your autonomous routine by setting the position to the desired state. I imagine you have something like this:
while (buttonPressed)
piston = true
which extends the piston only if the button is depressed. if you want a permanently extended piston, try just starting with piston = true.
Our concerns are that for this to work correctly the spike will constantly be pulling power which will drain our batteries quicker.
This is not much of a problem at all. The Spike isn’t seeing any load, so the current draw will not be significant. You could use the solenoid breakout if you are really concerned, but it’s seriously a non-issue.
Consider using a gas spring instead of a piston for this application - these don’t require power, just a mechanism to hold them shut before the match starts. Then again, it’s Week 6, so you might just want to keep what you have.
Also, if you are using the double action solenoid for this application it will stay in place (its last state) when the power from the spike is turned off.
The single solenoid requires a constant signal for the piston to stay extended, where as the double would have IN/OUT logic - trigger the solenoid, it goes out and stays out, trigger again and it goes in and stays in. It would require another Spike relay (one for the in and one for the out), but may alleviate the issue of constant (albeit small) current to the solenoid.
Using the double action solenoid as a single solenoid with a spike is possible with only one spike. One positive end would be on the M+ and the other would be on M-. Ground can be connected to the PD board. Driving M+ would flip the solenoid valve one direction, driving M- would flip it over the other direction.
Thanks for the help. We only have the single solenoids so that is what we have to deal with. It sounds like it would be better to have the double acting solenoids for future use.
We will probably continue to try to use the spike and program a toggle button on the joystick.
The reason that we are using spikes is because we felt more comfortable wiring them up that way, but we are also looking at using the solenoid breakout as well. At this point in time we will probably stay with what we have now though.