Thread: HVAC Control on Car PC through Serial Port.

Originally Posted by Chris31

I think alot of poeple will have problems attaching a servo/actuator to the control knob/shaft.

The controller must know how much to turn the servo/actuator by as well as how many stop positions. Attaching and mounting the servo can be a problem to most, non of them would be standard the way they work.

Not to put off you guys, I can just see problems comming in making a universal AC controller...it can be done though.

Take the knob off and attach one of these to the shaft:

Servo Shaft Adapter

Servo's are meant to be fairly precise (digital ones even more so) so getting them to go to the appropriate position isn't a problem.

Originally Posted by antimatter

The fan speed is not controlled by vacuum in my ford. It controlles where the air flows...foot/face/defrost

There is a mechanical switch to controll the fan speed

That is what i am trying to say .... this device will not change the air folw direction...

If i am correct then the vacuum system controls the flow of air.. in some cars they use cables for that .....

This unit just controlls the fan speed and the compressor.

I hope this clears things ..


Mastero

Originally Posted by Mastero

That is what i am trying to say .... this device will not change the air folw direction...

If i am correct then the vacuum system controls the flow of air.. in some cars they use cables for that .....

This unit just controlls the fan speed and the compressor.

I hope this clears things ..


Mastero

Originally Posted by antimatter

but i think what the purpose of the project is a bit more basic then total HVAC controlls

As i mentioned earlier your device is not an HVAC solution but more of AC solution. I think others in the thread were getting confused about this. Any way you look at it good work!

Originally Posted by antimatter

As i mentioned earlier your device is not an HVAC solution but more of AC solution. I think others in the thread were getting confused about this. Any way you look at it good work!

I know ... taught so too ...

Mastero

Originally Posted by White Night

Take the knob off and attach one of these to the shaft:

Servo Shaft Adapter

Servo's are meant to be fairly precise (digital ones even more so) so getting them to go to the appropriate position isn't a problem.

That is cool and all, but doesn;t solve the problem. The Motot must be mounted to something so that it doesn't. Attaching the shaft adapter to the shaft of the control knob for the AC will just have the motor protruding into free space.

Michael

Originally Posted by Wiredwrx

That is cool and all, but doesn;t solve the problem. The Motot must be mounted to something so that it doesn't. Attaching the shaft adapter to the shaft of the control knob for the AC will just have the motor protruding into free space.

Michael

That's true. There are a variety of ways to mount the servos. The best depends on the layout of the knobs. On my Jeep, a small hardware store bought angle bracket, some wood, and these little 90 degree mounts did the job. Mounting the servo turned out the be the easy part. Figuring out how to best connect them to the shaft took the research.

The hard part for me would be controlling the servo with the PC. It would take software and hardware working together. I have no experience with this. It would be nice to have HVAC controled by the PC but thats not what this thread is about.

Originally Posted by antimatter

The hard part for me would be controlling the servo with the PC. It would take software and hardware working together. I have no experience with this. It would be nice to have HVAC controled by the PC but thats not what this thread is about.

RC servo operates on PWM. If the knobs have 3 position, all thats needed is to find out whats the PWM values are to get to those 3 position.

For simplicity sake,

A 555 timer is used to generate the PWM. (Circuit can be found easily by googling)

3 variable resistor each defining the position of the servo can be used. One of the variable resistor is switched into the 555 timer by means of the bits from a parallel port.

Again, to make thing simple small reed relay are used to switch the variable resistors into the PWM circuit...moving the servo to the required position.

Its a ghetto way for non so techie poeple. Should work as well.


Ill never do it this way though

Originally Posted by White Night

That's true. There are a variety of ways to mount the servos. The best depends on the layout of the knobs. On my Jeep, a small hardware store bought angle bracket, some wood, and these little 90 degree mounts did the job. Mounting the servo turned out the be the easy part. Figuring out how to best connect them to the shaft took the research.

The servo-knob shaft adaptor is cool. I think its the filing/drilling/bending/glueing metals that might put off poeple from buying a servo driven kits.

I guess theres no other way though for such a system.