PWM damper actuators

[kuhnhunter]

Would somebody please explain how these acuators work? They are Belimo af24-pwm, 24v a/c d/c spring return.
They are on a Novar IOM/2 input output module.

[tripper]

PWM=Pulse width Modulation

Basically there will be an output to open & output to close the actuator, both being digital points.

the outputs are pulsed on a pulse/time ratio knowing the actuators drive time (unless it has feedback)

The af series i think are fire damper actuators, ie if you drop the supply off they will spring return to your fail position.

[universaloutput]

The actuator uses a set of contacts that close for a specified amount of time to position the damper. I think the standard range for the Belimo dampers is .59 to 2.93 seconds (you can order it with different ranges). Here's a sample of how it would work for a normally closed damper.

Seconds / Position
0.59 / 0% Open
1.76 / 50% Open
2.34 / 75% Open
2.93 / 100% Open

If you have a different PWM range you need to do some math to calculate the position.

These are also "spring return". The damper will maintain the position of the last signal, as long as it has power. When the power is removed, the internal spring will return it to its starting position.

[kuhnhunter]

Thanks that helps alot.