I am using an ssr to control a linear compressor for a berd-air part cooling system.
Standard pwm signal did not vary the compressor output (it only operated at full) so I added a full bridge rectifier after the ssr so now one dc pulse = one pulse of the compressor. I use the M950 Q command to vary the frequency of my compressor and then adjust pwm duty cycle to get the pump running smoothly anywhere from 1-60hz.
The problem is that it takes a lot of gcode post processing to make my part cooling fan work.
The reason I want to use this compressor is so i can use one "fan" on a tool changing matching with a standard V6 hot end and with a super volcano hot end, even laser air assist some day.
I think people laser cutting or even cnc routers could use these compressors if fan outputs could be switched to pulse frequency modulation with some sort of duty cycle