Heater flap control - Linear actuator / servo / stepper motor?

[catlotion]

I'd like to control an air duct flap on my heater remotely somehow (as part of a Bobil hot water heat exchanger project). The manual bowden cable isn't long enough to reach anywhere accessible and I'd like to automatically shut the flap when the water is up to temp.

I first tested some car central locking rams but they didn't like being energised too long and the motors burnt out. I might revisit those with a timer relay but thought there might be better options. Maybe stepper motor (could be over-complicated control for the 90 degree rotation I need), linear actuators (quite expensive), servos...?

Has anyone done something similar please?

thanks

 

[B27]

A servo intended for RC models maybe?
High torque versions are available.

 

[catlotion]

Yeah was thinking that but you need a PWM signal to trigger them so gets a bit complicated again...

this is what I'd really like but pricey!

Amazon.co.uk

 

[oilybilge]

That one is pricey, but you can get similar ones on Amazon for £30.

 

[B27]

You probably don't need 100Newtons of force?

An RC servo can probably be easiliy modified to respond to a simple DC voltage?
It's a motor drving some reduction gears an a pot for feedback.

Or you could just use the motor and gears and add some limit switches?
I had a car where the heater hot/cold flap was controlled like that, I can't remember which car it was, I can remeber trying to fix said heater.

 

[rogerthebodger]

I have used wind screen motors as the basis of valve and linear actuators

 

[catlotion]

ah yes - that's another good avenue to explore. Heater flaps and wipers...

might have a go at hacking the RC servo too. Too many options!

 

[chriscallender]

Yeah was thinking that but you need a PWM signal to trigger them so gets a bit complicated again...

this is what I'd really like but pricey!

Amazon.co.uk

PWM generators on Amazon are about 5-10 pounds (5 for a board, 10 in a case as well), and have an LCD display showing the duty cycle (=heater flap position). Hobby model RC servos usually operate on about 6 volts, so you might need to be careful about getting servos that can work at 12v, but otherwise it would be pretty straightforward.

Something like this could even control 3 flaps.

Amazon.co.uk

 

[catlotion]

that's perfect! I could only find servo tester type boards with a control knob for position...

Thanks