Controlling Hi/Low SSRs for air pumps

[Reista]

I'm using 3 separate pumps for part cooling, each with 2 speeds. They run on 120v and have a high/low switch which kills 1 leg to the motor. I'm planning on wiring them all in parallel with the low to SSR1 and high to SSR2. My question is, how can I get SSR2 to kick on when extra cooling is necessary?

I have in mind right now a PWM to analog voltage converter wired in series so when cooling is enabled low runs 100% and only at high PWM does the voltage become enough to kick on SSR2 but is there a way to do this in software?

thanks in advance.

[dc42]

Set up a thermostatic fan to turn on when extra cooling is needed (see M106), and connect the SSR2 control input to that fan output.

Note, the common zero-crossing SSRs may not work with motors, so best use the random fire type of SSR instead.