Get Pneumatic Pressure

Is there a way that the robot can read that pneumatic pressure from the pressure switch and then send that feedback to the smart dashboard?

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The pressure switch is a digital switch and doesn’t directly send the air pressure directly to the cRIO. I don’t believe it is possible to read the air pressure without a separate sensor.

You don’t have to add an additional sensor just calibrate the sensor for many different pressures, fit a function to these data points, and use that function to determine what the pressure is in the system. Most of this can be done in any spreadsheet program.

The pressure switch is just that, a switch, and not a sensor. It is commonly called a binary switch since it has a built in hysteresis. The circuit opens at ~115 psi and will not close again until the pressure drops to ~95 psi. So if you want to know the pressure you will need to instal a pressure sensor.

The Pressure Switch is connected to the Digital Sidecar therefore i thought you would be able to read the pressure that it is sensing. We wanted to know how much air we have in our tanks during the match.

The Q&A responded to pressure transducers last season…

Q428 https://frc-qa.usfirst.org/images/icons/bullet_blue.png Are pressure transducers (analog pressure sensors) legal for use on the high pressure side of the pneumatic system, in addition to the standard pressure switch used to control the compressor? Assuming that all specification (maximum pressure, etc) are met.

A: No Please see R82.

Please check the rules for this season for any changes.

Sorry to be brutal, but you thought wrong. It is a switch. It is either on or off. Nothing more.

Two suggestions:

  1. Mount some type of pressure sensing device for practices, practice a ton while carefully studying the pressure results you are interested in then remove the device for competition, but use the data.

or

  1. Mount your high-side pressure gauge in an area that it can be seen by your axis camera and read the pressure on your driver station laptop.

The Pressure Switch (http://www.andymark.com/product-p/am-2006.htm) reads the air pressure in the system and tells the shuts off the compressor when 120 psi is hit by communicating with the Digital Sidecar. That is why you specify the relay and digital input output port when coding. The relay is for the compressor and the DIO is for the switch that gives a reading and shuts off the compressor when that reading hits 120 psi. I have seen other teams read the psi using that but i wanted to know how we can do it the same way.

Here’s the data sheet for the pressure switch: http://files.andymark.com/NasonSMspecs.pdf. Each sensor is factory preset to a certain PSI that can’t be changed. It only outputs a digital/binary signal; it does not report the actual pressure to the cRIO.

Have you looked at the methods for the compressor class?

Thank you Joe! I don’t know why I didn’t start there but I found a way to do it. Thanks.

Everyone, please understand that the 120 psi specification is not a hard spec. In my experience (watching during inspections) it is more likely 120 +3/-5 psi from unit to unit.

I wonder if it’s the right time of year for the GDC to consider a 2014 rule allowing any pressure sensor rated for the pressure in the system at that point of installation. (If it would replace the switch, it would have to be rated against all failures; if it would supplement the switch, non-operation is not important, so it would need only be rated not to be pneumatically compromised in normal service.)