Digital air conditioner control for daily car, possible with arduino ?

Hi; I have a daily drive which is fiat punto and it has manual controlled heater-aircon. I want to convert it to digital with using arduino.

There will be two control ; one of them is temperature control , second one is air vent positon control

First one;

Regarding to temperature fan motor speed will be controlled . For ex;

In side temperature is x, adjusted temperature is y. if |y-x| > 6 degree run at speed 3 if |y-x| > 4 degree run at speed 2 if |y-x| > 2 degree run at speed 1 if |y-x| > 0 stop the fan

Second one;

There is 6 position on heater vent system for 30-40 degree movement of servo motor is enough for position change. every 30 degree position will be cgange i need forward and backward buttons to control it.

LCD pnale will be added system in order to see system data.

As a result is it possible with arduino :=)

Regards Ercan

In my experience, things like car heater controls and switches tend to need quite high forces to operate. I think the most difficult part of this project would be making an actuator for each control that can generate enough force to move the control and position it accurately. I guess you would dismantle the existing dashboard controls and reconnect whatever cables etc they operate to some control box that you would construct, which would contain heavy duty rotary and/or linear actuators.

From your description it seems unclear what the two controls are. Is your 'temperature control' just something that varies the speed of a fan? I thought this might be something that either moves a flap to mix heated/unheated air, or engages an aircon pump. From the point of view of the Arduino I don't suppose it matters much - as long as it is clear in your own mind what the controls do and what algorithm you want to use to control them, and you have suitable actuators installed to operate the controls, all that's left is to make/buy the driver circuits for the Arduino to drive your actuators, and program the Arduino to implement your control algorithm. The last two things are definitely possible. The rest of it - only you can judge.

I agree with PeterH, when you say

I want to convert it to digital with using arduino.

that suggests you want to change rather than replace the existing system, and the manual systems are clunky and need a lot of force. It would probably help people if you said what your mechanical and electrical skill levels are and what sort of tools you have available.

Could an arduino control air conditioning - yes. However there could be a lot of work involved, much more than just moving the lever up and down by hand, so is this for fun?

Hi all,

New here and new to this world of Arduino.

I was searching for this topic, and thought I would revive this thread vs start a new one...

I have fairly decent electrical skills, better mechanical skills, can follow plans and diagrams.

I, too, would like to control my car's airconditionng with a digital controller. Unlike the original poster, my car's air conditioning system is vintage and very rudimentary. The car is a 1971 Mercedes Benz 280SE, and the A/C is basically an under-dash add-on. The heater is totally separate from the A/C.

The current A/C is composed of a blower (12V, squirrel cage fan with 7A motor) and obviously the compressor and its pulley/clutch.

In the cabin are two knobs, one is attached to a rheostat/potentiometer which gives variable fan speed (not 0-1-2-3 as in normal cars, but rather "Off-100%-~10%") and a second knob which controls the pulley/clutch to engage the compressor, via a thermocouple and mechanical switch.

My basic thought is that I can use a PWM or maybe a rotary pot (both + and - directions) to control the blower, and maybe two buttons or a rocker to control the cut-in/cut-out temp for the compressor, and of course a power on/off switch for the controller and system. Am I correct in this train of thought, or should I be heading in a different direction?

I envision it working like this (car already running and supplying 12V power)

Turn on the system switch. This provides 12v to the PWM for the blower if I don't use a rotary pot, and powers up the digital temp controller (arduino-based?). Depending on the delta between set temp and the actual temp, a relay would be activated which engages (then disengages, when appropriate) the compressor. The blower speed would be constant based on PWM or Pot setting.

I greatly appreciate thoughts and alternate suggestions.

Thanks much!

Sounds good. How about a second pot to specify the set temp?

Palolo: In the cabin are two knobs, one is attached to a rheostat/potentiometer which gives variable fan speed (not 0-1-2-3 as in normal cars, but rather "Off-100%-~10%") and a second knob which controls the pulley/clutch to engage the compressor, via a thermocouple and mechanical switch.

I suppose the rheostat is a big clunky thing that is simply in series with the fan motor - I don't see any problem replacing that with PWM as long as you use a beefy enough driver circuit with the proper EMF protection. I don't quite get how the clutch control works but I guess you have a mechanical otter switch or similar with significant hysteresis that operates some sort of solenoid to engage the clutch. You should be able to control that electronically, too. I'd be wary of using too high a PWM frequency on the clutch control since this cause accelerated clutch wear, and you probably want to switch a few times a minute rather than a few times a second. A technique used on modern central heating controllers is to work out the duty cycle needed to maintain the required average temperature, and then apply that duty cycle at a relatively low frequency - for houses, the period would be tens of minutes because the heating system has a huge thermal mass; a car might respond quicker and need a higher PWM frequency, but I suspect still a few times a minute rather than a few times a second.

Given the control sophistication possible on the cooling side, I hope you're considering doing similar on the heating side to give full climate control. :)

Hello from Portugal!

I'm posting here because I have a similar issue.

I own a brittish car (MG), steering wheel on the left side but designed for normal brittish right hand side wheel. Climate controls are quite ruddimentar and when I turn the knobs on the dashboard there's a steel cable that get's pulled/pushed. Because of the right hand side design but left hand side assembly, these steel cable have a stupid curved path and I need to use force to rotate the plastic knobs. Sometimes they brake, which is quite annoiyng.

So, I'd like to get rid of the steel cables and use servos (or steppers) instead. Can you give some guidance, please?

  • The 1st knob is a rotary switch for the fan speed. Ok, no steel cables here but I'd rather have arduino control it. The fan has off+3speeds. I know I can replace this rotary switch using 3 relays connected to arduino. Is there a better way?

  • This 2nd knob controls the temperature by opening a valve and letting the hot coolant flow from the engine. I think I can mecanically adapt a stepper to push/pull this valve.

  • The next knob controls the direction of the air: legs, head, front window. the steel cable again pushes/pulls a flap. I think I can use a servo (or stepper) to push/pull the flap. But this movement should be horizontal instead of rotational. How can I use the rotation to make an horizontal movement? Is there some kind of standard gear+screw that one hooks to the motor and gets the desired movement?

So these are my questions: how many arduinos do I need to control 4 motors? Do I really need a motor shield? should I use servos or steppers? How to replace a rotary switch (using 3 ou 4 relays)? How to have horizontal displacement?

Thank you very much!

DonGiovanni: The 1st knob is a rotary switch for the fan speed. Ok, no steel cables here but I'd rather have arduino control it. The fan has off+3speeds. I know I can replace this rotary switch using 3 relays connected to arduino. Is there a better way?

Yes, PWM.

How can I use the rotation to make an horizontal movement? Is there some kind of standard gear+screw that one hooks to the motor and gets the desired movement?

Remote control airplanes translate rotational servos to linear control surface motions all the time. You just need a crank: http://en.wikipedia.org/wiki/Crank_(mechanism)

So these are my questions: how many arduinos do I need to control 4 motors?

One.

Do I really need a motor shield?

No, you could use transistors instead. Motor shield is more convenient though.

should I use servos or steppers?

Servos.

Wow! thank you very much Tylernt, your answer enlighted me. But I'm such a rookie that I'll need some more advice, please.

1) Using PWM instead of relays is quite clever. But I'll need some kind of driver:

Input: automotive DC 13V ____ Input: PWM from arduino ____ | DRIVER |____Output: AC 13V with matching frequency to fan

Does it exist? and will the fan motor accept it? I searched and I only found industrial type VFD(variable frequency drivers). This is also very clever http://forum.arduino.cc/index.php/topic,75727.0.html but I can't use it.

2) The crank idea is great. Thanks! I'm also considering a screw pole instead. I think I'll try both and see which works better.

Kind regards!

Surprised if the blower motor were AC. All of the automotive motors I'm familiar with are brushed DC, which can easily be PWM'd with a common transistor.

Thanks again! I'll try a Darlington transistor. I suppose a TIP120 will work. I'll update the progress. Kind regards