Pneumatic pressure switch

[M. Hicken]

Im not sure if this should be in the programming or pneu thread.

Forgive me if im wrong, i havent slept in about 23 hours.

When i was paging through the manual, did I see that the code for the pressure switch is not in the default code? I can not say i know a great deal about coding, im crossing over from the mechanical threads. But is it in there? and if not, how is one supposed to keep pressure? i dont think trying to keep taps on how many times you fire the cylinders to how much time you charged the compressor will work well, untill someone blows the relief valve.

sorry for rambeling, i cant see straight

[Chris Fultz]

The pressure switch has two settings.

At the high point (115 - 120 usually), the sensor will send a signal to the control. At this point, the compressor should be shut off.

As you use pneumatics, the pressure will drop. When you reach the low set point (100 - 105 usually), the compressor will come back on. Unless something malfunctions, you should never trip the relief valve.

[M. Hicken]

nono, i know how they work, they will cut back on at 95 psi. my question is, is that coding in the master default code. i couldent seem to find it, or am i thinking about it too much, and it is an on off switch, and no coding needed?

[ldeffenb]

Code for compressor control has never been in the default code (believe it or not). What *is* in the default code is software that turns on and off defined relays in response to defined digital inputs. There is also code that outputs values to defined PWM channels based on input values from defined joysticks. Various other digital inputs are coded to provide limits on some of the joystick to PWM "connections".

It is up to the hardware designer to figure out which digital input the pressure switch should be connected to and which relay output the compressor should be driven from. Then you can run the default code.

Otherwise, your hardware designers can tell the software folks which digital input will be the pressure switch and which relay will be the compressor and custom software will need to be written to monitor the state of the digital input and drive the state of the relay to accomplish a control loop.

The default code is sufficient to implement a robotic control system, but you need to wire the controls to fit within the "connections" made between inputs and outputs as defined in the default code reference manual. Nothing fancy is included and no autonomous mode is present.

To get autonomous mode stuff, you go to kevin.org for the PID control loop and command sequencing stuff. That code has its own assumptions about what inputs and outputs are connected to what. It must all be read and understood before anything is actually wired in and/or software loaded.

That's where the rubber meets the road (or the tires meet the carpet) and the real fun begins!

[Biff]

[quote=ldeffenb]Code for compressor control has never been in the default code (believe it or not). What *is* in the default code is software that turns on and off defined relays in response to defined digital inputs. There is also code that outputs values to defined PWM channels based on input values from defined joysticks. Various other digital inputs are coded to provide limits on some of the joystick to PWM "connections".[quote=ldeffenb]

Last years default code did have relay control defined, for the last relay and the last digital input, as I recall. I also remember that the positive and negative were reversed in an early version. The spike driving the compressor was Red so the fan on the compressor ran backward. I do remember reading the comments in the code telling you where to connect the spike and the switch. Can't say the same for this years code as I haven't looked yet. If you want all the details search the old forums Or look in 2004's default code.

[Joe Ross]

The pressure switch code is in the 2005 default code. It's so simple that it's easy to miss.

relay8_fwd = !rc_dig_in18;  /* Power pump only if pressure switch is off. */

Hook the pump to relay 8 and the pressure switch to digital input 18 and you're good to go.

[sirbleedsalot]

How are we supposed to connect the pressure switch to digital input 18?

[Robby]

Originally Posted by sirbleedsalot

How are we supposed to connect the pressure switch to digital input 18?

all you have to do is cut the end of a pwm cable off and connect the two wires to the switch and the other end of the pwm cable to the controller on a digital input.

[sirbleedsalot]

Which wires do you hook up to the switch though? Red, white, or black?

[Mark McLeod]

Originally Posted by sirbleedsalot

Which wires do you hook up to the switch though? Red, white, or black?

The pressure sensor/switch has two contacts. One of these (either one) connects to the ground pin (black PWM wire) on the RC, the other connects to the Signal pin (white PWM wire).
The center +5v or red wire is not used for this purpose.