Compressor, Pressure Switch, and Analog Pressure Sensor

The Compressor#

The compressor is the only legal source of compressed air on the robot — you may not bring pre-pressurized bottles. A common, legal choice is the VIAIR 90C 12V compressor, sold through AndyMark; its manufacturer spec lists about 1.03 cfm (AndyMark bench data shows ~0.88 cfm at 0 psi, dropping to ~0.22 cfm at 110 psi). Rule R806 caps compressor flow at a 1.1 cfm nominal rate at 12VDC, so make sure your compressor's spec sheet stays under that.

The compressor produces heat and vibration. The Pneumatics Manual recommends mounting it on its preinstalled vibration-isolation feet attached to a stiff surface, keeping it from touching anything it could melt, and even fanning it during back-to-back matches so hot output air does not soften nearby tubing.

How the System Knows When to Stop#

The controller runs the compressor until a pressure feedback device says 'full,' then shuts it off automatically. There are two feedback options:

Digital Pressure Switch#

The classic choice is the Nason SM-2B-115R/443 pressure switch. It is a simple on/off switch wired to the controller's pressure-switch input. It opens at roughly 115-120 psi (stopping the compressor) and does not reclose until pressure falls to about 95 psi (restarting it). That built-in hysteresis keeps the compressor from short-cycling. The PCM uses a digital switch; the PH accepts one too. Polarity does not matter — it is just a switch.

Analog Pressure Sensor (PH only)#

The REV Analog Pressure Sensor (REV-11-1107) is a transducer wired to one of the PH's analog ports. Instead of a single on/off point, it reports the actual pressure (default 0-200 psi mapped over 0.5-4.5V), so your code can read live pressure with getPressure() and set custom compressor on/off thresholds (for example, run between 70 and 120 psi). This is the PH's standout feature.

Safety: The Pressure Relief Valve#

Independent of any electronics, a mechanical pressure relief valve must be connected directly to the compressor with hard fittings and set to release at 125 psi (R811). It is your backstop if the switch or sensor ever fails to stop the compressor — pure mechanical safety that needs no power.

Required Gauges and Vent Plug#

Your system must show two pressures on gauges — stored and working (R810) — and include at least one vent plug hand valve (R813) so you can safely dump all stored air before working on the robot. These are inspection requirements, not optional niceties.