strange servo behaviour

I've nearly finished my heatermeter and currently testing on the bench.

I'm using the microdamper and have wired it up as;

Fan Neg - Brown
Fan Pos - Blue/White
Servo Neg - Brown
Servo Red - Green/White
Servo Orange - Green

the fan seems to operate correctly, at setpoint 0 fan is full on. At setpoint 200 fan is stopped.

The servo doesn't seem to move when setpoint = 200, but when I change it to 0, it spins constantly?

Just realised the servo is an mg90s (digital), I guess I need an analog servo?

Bryan Mayland

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The servo continuously rotates, as in more than 180 degrees of travel? Digital servos are fine, the "digital" part is on the output, not the input. If it just rotates and rotates then that is a continuous rotation servo, not a .... errr what are regular servos even called?

Setpoint of 0 should actually be manual output mode 0%, so I don't know what's happening if your fan is on at 0% and doesn't run at setpoint 200 (unless the pit temperature is over 200 obviously).