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matlocc

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Reply with quote  #1 
So I have 2 students that have really jumped into this.  I was talking with them about the cool air moving in at night and the need for blocking the vent.
One kid suggested a damper controlled by a car lock actuator (because we are using a 12 volt fan system)  He said to have it turn on when the fans went on opening the damper and then when the power went off have a spring assist return to close the damper.  Has anyone done anything like this?

stmbtwle

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Reply with quote  #2 
I think a car lock actuator would work well, BUT...

I have a few and I've done some experimenting with them. They have plenty of power but are only designed to operate for a fraction of a second. If used to hold a vent door open they will likely burn out.

The door could be designed to stay open once opened, but then a reverse circuit would be needed to close it.

An alternative would be a resistor in series with the actuator to reduce the current to a "safe" level, but this will also reduce the power.

Another method would be a limit switch with a "hold" resistor. You'd have full power to open the vent, but once limit was reached, the resistor would reduce current to a safe "hold open" value.

Still, lock actuators are cheap and readily available, and IMO well worth investigating.

The easiest system might be a cloth flapper "valve" that will operate by fan pressure, or a collector design that does not siphon.

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Rick H Parker

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Reply with quote  #3 
I would be looking at the electrically controlled fresh air vent on a car. The fresh air vent is a damper ....
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Rick H Parker
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stmbtwle

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Reply with quote  #4 
It's a great idea, BUT it's easier said than done. The ones I took apart had several wires and a circuit board. I burned up both of them and never did could get one to work. Might have to contact the auto manufacturer for a wiring diagram.
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gbwillson

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Reply with quote  #5 
A dealership MIGHT have the wiring diagram. But then again, it's more probable that they would simply replace the unit without trying to track down a fault. Doesn't hurt to ask...
Rick H Parker

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Reply with quote  #6 
The ones I took apart had several wires and a circuit board.

Stepper motor and control board. You got to figure out how to command the control board not power the motor.

A dealership MIGHT have the wiring diagram.

Or find them online.

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Rick H Parker
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stmbtwle

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Reply with quote  #7 
All well and good, but as I said, easier said than done. They're on Ebay if one can figure them out.

Simpler would probably be an ordinary hobby servo. Either one would probably require an Arduino or similar processor. The "nano" can be had for <$10, and coding is online.

If anyone knows how to control one DIRECTLY with a pot or thermistor (no processor), it would be handy to know.


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Rick H Parker

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Reply with quote  #8 

You cannot control one with pot or thermistor. One needs to step the motor by jumping from coil to coil. That why a controller is used. One could control a stepper with a rotary switch. You don't run a stepper motor, it is step and hold forward or backwards.

[200px-StepperMotor]

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Rick H Parker
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stmbtwle

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Reply with quote  #9 
I know how stepper motors work, I used to work with them.  Never had to try to control one though.  I know servos have some sort of feedback circuit to determine where the motor is, and move it if necessary (this can be done without a stepper motor) and I was hoping that they might respond to an analog signal.   I'm beginning to think that flapper actuator is just another servo.

OK what's the difference between an "analog" servo, and a "digital" servo?  Or is it just marketing BS?

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Rick H Parker

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Reply with quote  #10 
I'm beginning to think that flapper actuator is just another servo.

A servo cost more and a flapper does not need the precision of a servo. You can figure out the rest.

Steppers have a zero reference sensor, from there it is accounting.

OK what's the difference between an "analog" servo, and a "digital" servo?  Or is it just marketing BS?

The signal is processed digitally, by a microprocessor, on the "digital" servo. The "digital" servo has a higher resolution which makes the output closer to analog then the "analog" servo. It like call a square wave inverter an analog inverter and a modified sine wave inverter a digital inverter.  





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Rick H Parker
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