Automotive Air Conditioning Control

Projects General Guidance
1

Hey all,

I am relatively new to Arduino and have loved every second of it so far! I have a fair understanding of electronics so that defiantly helps me along the way.

I have a bit of an unusual project for my arduino, I am restoring a Morris Minor panel van and it was modified (badly) when I got it so I am redoing a lot of it but keeping it modified (that's a whole other story). Basically I want the outside to remain as close to original as possible but design a custom, more modern interior. My arduino projects for the car are to control the fade in and out of the interior LED lighting, an LCD display screen to display the time, inside and outside temp and also if a door is open. Its been a lot of fun so far (most of the time :slight_smile: ).

My main question here is to please request advice, I am installing an air conditioning system from another donor car, This system still maintains it original equipment, however I would like to convert the existing cable pull system that directs air flow to a more friendly electronic system controlled by the arduino. I am not really sure on the best way to do it, I have a basic "Google education" on how servos and linear actuators work and thought this may be an option. What I need the system to do is control the air direction vents which require the actuator (or whatever is suggested) to move in a linear manner and stop in four or five predetermined positions depending on the position of the switch in the cab. I am pretty sure that I will need it to have feed back of some variety as I will want the switch to determine the position every time reguardless of the state of the arduno, if the switch is moved while the battery is not connected then when power is returned the actuator returns to the position shown on the switch in the cab.

If somebody could please suggest a few options and if possible where I could find some good material to learn more about this. Even some examples of the equipment i could use and code to control.

Thanks a lot in advance.

Lee

2

I guess it will depend fundamentally on the forces and distances involved, but if your cable system is light enough to be operated by an ordinary radio control servo then this is trivially easy to control from the arduino. Your sketch just tells it what position to go to, and it goes to it. Most RC servos are lightweight and might not be able to provide enough force to operate a heavy mechanical system, but there are some heavy duty servos available for bigger models that can handle quite high loads.

Failing that I think you'd be looking at the sort of linear actuator / position feedback system used for CNC controllers and that type of thing - conceptually very similar, but needing a bit more work on the mechanical side and also on the software side. Still not especially difficult though.

3

Hi PeterH,

Thanks a lot for your reply, I am not really sure how I can measure the linear force but I guess I can always give an RC servo a go.

If I need to use a linear actuator, do you think the firgelli L12 actuators would do the trick and be ok to control with the Arduino?

Also mate, do you know if I can use the Servo Library for these actuators?

Thanks again

Lee

4

I assume you're going to dismantle the control system to get access to the cables that you want to operate. Once you've done that, just operate the cable by hand and measure how far it needs to travel and what force it needs. In my experience these mechanical control systems typically get much stiffer in some positions and suffer from a lot of stiction; it's the peak force required that you are trying to measure.

Once you know the travel and force you can compare that against the spec of the available servos to see if any of them are up to the job.