Arduino controlled automatically actuated grill block
 

(NOTE - Nov, 2012 - the original grill block described in the first part of this thread didn't work well. Jump to post #94 to see the redesigned version.)

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I've been poking around with the Arduino for a little while trying to figure out how to get this project to work. I've compiled a bit of info on it, but Darin finally bugged me enough to get me to post the info as some help definitely wouldn't hurt. Also, this is by far not an area of expertise (electronics) for me. I know just enough to start getting me into trouble. I've only gotten this far through a lot of web surfing and reading up on things and some help from dcb (thanks again). So, I'm throwing out my initial designs for you to all look at, tear apart, and come up with something good we can all use.

Anyway, this is the general idea. Use the arduino to monitor a temperature sensor. This is an additional sensor (no splicing into existing car wiring) will be monitoring coolant temperature. It will be mounted in a radiator hose coupling that will need to be spliced in after the thermostat. Monitoring the temperature from this sensor, the arduino will output commands to a h-bridge which will control a simple two wire electric door lock actuator. This actuator will close and open the grill block door. Sounds pretty simple eh? Well, its not, at least not for me. :)

The current problem I'm having is finding an acceptable h-bridge. Almost everything I seem to find is surface mount, and I'm not even exactly sure what specs to look for in this thing. I think I found an acceptable one. Its the TLE 5205-2. Its in a P0-220-7 case so it can actually be worked with. The down side is its (I'm guessing) overkill as it can handle 5A continuous, and its also a bit pricy at $7.50. As I was browsing mouser and digikey there were a lot of cheaper chips, but as I said, mostly surface mount. I'd obviously like to keep the price down where ever possible.

Here is the list of necessary items:
Arduino of your choosing
LM61 temperature sensor in a TO-92 case
Electric door lock actuator
h-bridge
radiator hose coupling (local automotive store, mcmaster)
wire
grill block of your design


I have most of the arduino coding done, but I'm not going to bother posting it as it may change depending on the h-bridge.

All in all, I think this can be put together fairly cheap. I've looked into other ways of doing this and this is easiest, most customizable and cheapest way I've found.

Awesome idea!! I'll be watching the progress of this one...

Agreed - fun project.

Remind us again what the h-bridge does?

The h-bridge is a neato chip that will help me control the actuator. To understand why I need it I'll explain how the actuator works. The actuator is a really simple and dumb device. It only has two wires. You apply voltage to lead 1, and ground lead 2 and the actuator extends outward. If you apply voltage to lead 2, and ground lead 1 the actuator tries to go back inward. Its not even smart enough to cut power after its already fully extended, it just keeps trying to go out (or in) even once it has hit its internal stops. Anyway, the h-bridge lets me take two output pins from the arduino, hook them up to the h-bridge, and control the actuator. The h-bridge does the polarity reversing for you based on the inputs it gets from the arduino. It also handles the amperage needed to power the actuator kinda like a mosfet or relay would. If you tried to power the actuator with the arduino it would burn it out.

Gotcha. Thanks for clarifying.

Interesting idea. You need to plumb your sensor not only after the tstat, but after the radiator as well. You want to know how hot the coolant is before it goes in the motor, not after the fact. This will give you a little safety factor. You also need to allow for overlap in the temps. In other words, door opens at 220 degrees and closes when at 210. Otherwise, hysterisis will take place and door will get "confused".

Interesting... that's actually what I thought the "h" in "h-bridge" stood for... hysterisis... Tells you what I know... :p

How about just have it open when the electric fan comes on? If you have an electric fan of course.

My guess is that you would end up having the fan coming on and off constantly. It would cool as normally, due to the grille being open, but things would heat up rapidly upon the grille closing. Having the motorised grille block open at a temp below the cut in temp of the fan would help level out the temps before the fan cuts in. What would be really "cool" would be to have it on a servo motor so the grille could close by an amount that would hold the temps at a pre-determined level. As you'd drive through cold pockets of air, it would close slightly and vice versa. Awesome!:D

ollie

Good point and cool idea.

I don't think just any grille block design would work with a door lock actuator. At some point I imagined having just a cover that hinges forward to open, but I think a door lock actuator wouldn't have any holding force once the voltage is removed. Maybe a grille block with a sliding slotted door would be good.