Arduino climate control

[Scottfunk]

I'm asking this because I know there are a lot of tech savvy people on this forum. I'm building an arduino based climate control system for my Yukon because I no longer have vacuum. I have built an app to control the system that consists of three slider bars (fan speed, temperature control, and zone control.) Controlling the fan and the flapper door haven't proven to be too difficult, however the coolant diverter valve has turned out to be a different story. Does anybody have any useful suggestions about how to control this with an arduino? The tech guy from the company I talked to said the direction of the diverter valve is changed by changing polarity to the motor. Can this even be done with an arduino? And how do I boost the signal from the 3.3V coming out of the arduino to the 12-24V needed by the valve? The pot is just feedback to the arduino letting it know what position it's in, like a tps. It's mostly just the polarity swap I'm not sure how to do.

Edited November 24, 2017 by Scottfunk

[kzimmer]

Can you use two digital outputs from the Arduino, both triggering relays? One output for open, triggering a relay that switches +12v, the other for close, triggering -12v. If you do, get a relay with auxiliary contacts so you have a little bit of protection. Like a forward/reverse motor starter circuit.

Edited November 24, 2017 by kzimmer

[Mopar1973Man]

I'll have to go look at the winch relay system on my ATV. I'm using two 30 Amp relays for that with a single switch. 12V power from the battery. The two relay is capable of forward and reverse actions on the winch so basically, you just need to duplicate that. 

 

 

Edited November 24, 2017 by Mopar1973Man

[Scottfunk]

I promise I'm bout trying to be dense here. I see how this circuit provides power too the wench, but on the negative side what is providing the ground? Is the 87a providing connecting to ground when the relay is not energized?

[Mopar1973Man]

Basically. the two relay in neutral look like this one.

 

So when neither relay is powered it will have ground on both sides of the winch motor. So now if the switch is grounded on the green leg now that will trigger the first relay and the green lead to the winch now is POSITIVE while the blue lead is NEGATIVE. So if it reversed only the blue wire of the switch is grounded now the blue wire to the winch is POSITIVE and the green wire is negative.

 

There can only be 3 states on the switch.

1. Neutral - Both the green and blue wire of the winch are NEGATIVE or ground.
2. GREEN GROUNDED - now the green wire to the winch is POSITIVE.
3. BLUE GROUNDED - now the blue wire to the winch is POSITIVE. 

[Scottfunk]

Do you think there's a way to accomplish the same thing but with some transistors and a couple diodes? I don't think an arduino will even power a relay. The power I'm dealing with here if so small, plus I believe the motor is pwm which can be problematic through a relay. 

[kzimmer]

Here is a really fast and crude diagram on how this could be accomplished. I apologize for the chicken scratch. There is definitely more than one method to accomplish this. This is one.

[Scottfunk]

Actually that just might do it. It's probably a stepper motor which shouldn't need speed control only off and on. I'll try it out

[kzimmer]

If it's PWM you might be in trouble.

[Scottfunk]

I'm still waiting on it to arrive but I don't see why it would need to be. Just has to go from point a to point b then stop. I think I can build the circuit @kzimmer drew and replace the coils with transistors. Basically create one path from positive to ground when one pin goes high and a different path (opposite) when another pin goes high. Thanks so much for the help I'll update when I get it worked out. I'm hoping to offer this as an upgrade to the old style lever system when it's done with the added bonus that it doesn't require vacuum

[Me78569]

There are various arduino relays that trigger off of 3.3v for a 12v pin  I use it to control my lockup switch and eb logic

[Scottfunk]

@kzimmer your drawing led me to this. It's pretty rough cuz I'm at work but I think it might do the trick. Four transistors. This way if it's pwm I'm still in business. Since this motor only turns 90 degrees there's a good chance being able to control the rate of travel will come in handy. What does everyone think?

Edited November 24, 2017 by Scottfunk