I'm building a 1968 Roadrunner and I want to use an Arduino to control the HVAC. The original use a push button vacuum switch, a cable and a 3 speed switch. None of these parts are available so I'm thinking using my control button and spring load them and when pressed they push a micro switch. I can write logic so that when any button is pushed the last command is stopped and a new command is entered. Most of this seems pretty straight forward. Where I've not been able to get info is on the blower motor control. I want to replace the 3 position switch with a pot and use the varying resistance to set a pulse width and use that to control the blower speed. This would make it like new car that have a near infinite speed control. What I'm not able to find out is what/how to drive the blower motor. I figure I would need to use a MOSFET that would be controlled by the Arduino but I don't know what would be for this or the circuit needed. Most cars have about a 20 amp fuse on these blowers so I would need to cover that amount of power continuous. I've looked at projects, Makes, Instructibles, forums and while I seem things that get close nothing uses this amount of power. Can anyone give me some direction on this?
I'm just getting started with Arduinos and I see a lot of uses as to a car or hot rod. Remote door locks using a cell phone via bluetooth, keyless enter and run with RFID, wiper delay, auto headlight dimmer, just to name a few.
Instead of a pot for reading input, I would consider a rotary encoder, but a pot will still work. As for speed controlling the motor, would a high amp hobby speed controller not do the job?
I had not thought about a hobby speed controller. I've seen those before for the 3 phase motors, I guess they make one for a DC motor. I will have to look up a H-Bridge DC motor driver, that is why I asked the question is because I know it can be done but I didn't know how to do it. Thanks for the suggestions.
You just need a transistor to switch the fan. If you drive the fan from a pwm output it will give you pwm speed control .
So just scale the reading from your pot to the pwm ( analog) output .
Google transistor as a switch
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You can get hobby speed controllers for brushed DC motors, although I do not know if they would withstand the long-term usage needed for a blower motor in a car. I'm sure there are similar industrial rated controls. Traditionally blower speed in a car was done using resistors in series with the motor (actually short coiled resistance wire, usually placed in the path of the blower output to help cool the wire).
jedirick mentioned a H-Brdge DC motor driver and in looking at how to make one of these I came across a Half-Bridge DC motor driver which is half the H-Bridge in that it is not reversible which is fine for what I want. It uses 2 MOSFETs and the circuit is really simple and can be driven off the PWM circuit from the Arduino. I could use resistors like the factor does but that locks me in on 2 or 3 set speeds and I wanted it more a variable speed like new cars have. I still have research to do but I think I have a good path now. Once I get started on this and a few other things I was thinking about for this car I will post them here. Easy to see it is a great place to get help and that is something I will need.
Seems like a fun project. Will the car have A/C or are you just looking for fan and blend door control?
You could use a pot input to control a PWM fan controller. You will have to raise the PWM fequency to keep the motor from whining. The arm that was contolled by the cable can be manipulated with a servo. imagine you want everything to look stock.
You could use an Arduino to run most every system on car I would think.
The car has A/C but I'm planning to use one of the new modern Sanden compressors and use an expansion valve to control freon flow so the compressor just stays on. I've set some up like GM did with the orfice tube and pressure switch but it cycles the clutch too much. The factory GM compressors are built for that but most others are not and will wear out quickly.
I was thinking PWM on the fan control and also let the Arduino do blend door control. I've looked at the servos and there are also vacuum solenoids that can be used to control diaphragms on the doors, old style. Only thing about that is the door is either open or closed, no half open.
Other things i had though about is the way in a newer car you turn and release the key and the engine continues to spin till the car starts, automatic lights, auto dimming head lights. Funny how many things you can think of to use the Arduino on in an old car.
I also have a 1984 Mustang SVO and I think I'm going to try the Speeduino Engine Management on it. It currently has what Ford first came up with and the Mass Air Flow Sensor is a vane in the air flow that moves a contactor across a coil to decide air flow. Pretty primitive.