HVAC system conversion to servos!

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SirFoxx
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Posts: 81
Joined: Sun Feb 05, 2017 5:42 pm
My tercel:: 1981 Toyota Tercel w/ 7age

HVAC system conversion to servos!

Post by SirFoxx » Sun Nov 10, 2019 2:22 am

Converted the hvac system in my tercel to use servos! As a heads up, the lovely radio wiring was done by the previous owner haha.

https://www.youtube.com/watch?v=IBqqyH_ ... e=youtu.be
1988 DLX Tercel Wagon w/ weber (RIP)
1985 4wd Tercel SR5 (RIP)
1981 Toyota Tercel

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SirFoxx
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Posts: 81
Joined: Sun Feb 05, 2017 5:42 pm
My tercel:: 1981 Toyota Tercel w/ 7age

Re: HVAC system conversion to servos!

Post by SirFoxx » Thu Nov 14, 2019 2:50 am

I know there isn't much interest, but I figured I'll upload some pictures of the controller. I'm super unhappy with the paint I picked. I thought it was matte black, but it was actually glossy.

For the people who haven't watched the video..

I converted my HVAC controls to use rc servos. When I got the car, all of the HVAC cables were seized, but the levers moved. However, when you move the lever, it actually is bending it. So, that left me with a temp range of warm to warm, and barely any vent control.

Voltage regulator is mounted to the bottom. It's set to 7.5v due to servo limits.

Arduino Uno is a programmable microcontroller. It reads the button inputs, and tells the servos to move within the user set limits.

Red and blue buttons are for the temp servo, green and orange are for vent direction servo.

Toggle switch is for coolant valve.

I'm reusing the AC button and blower motor switch.

The only HVAC control that is still cable operated is the recirc door. I always have mine on recirc, so it doesn't really need a servo.

For those saying "well, this is a first gen tercel, it won't work on a second gen tercel!" I'm like, 99% sure the HVAC system is identical between the two generations. Just like the drivetrain is.
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1988 DLX Tercel Wagon w/ weber (RIP)
1985 4wd Tercel SR5 (RIP)
1981 Toyota Tercel

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NWMO
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Re: HVAC system conversion to servos!

Post by NWMO » Thu Nov 14, 2019 7:33 am

Keegan,

Thank you for the video and pics. My older son was in a robotics club (FIRST tech challenge) for two years in HS, so I have a limited knowledge of the components, etc. I assume you wrote a basic program for limit control. Did you use Android studio and JAVA programming? The home position is basically your first line of code, setting the servos to a start position?

We never got into the coding as much as my son wanted, the fellow leading the group found it easier to program himself, and we usually concentrated on the robot engineering to accomplish whatever that years challenge tasks were. Nice work, let us know how it holds up after you're back on the road please. I drove one year without much heat before deciding to clean/service/repair my system, it works much better now. I was going to link that discussion but I had a lot of photos that have been blurred by the "Photobucket Plague". If I can find the time, I will see if I can get away from the links and clean that thread up.

Chris
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SirFoxx
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My tercel:: 1981 Toyota Tercel w/ 7age

Re: HVAC system conversion to servos!

Post by SirFoxx » Thu Nov 14, 2019 10:21 pm

NWMO wrote:
Thu Nov 14, 2019 7:33 am
Keegan,

Thank you for the video and pics. My older son was in a robotics club (FIRST tech challenge) for two years in HS, so I have a limited knowledge of the components, etc. I assume you wrote a basic program for limit control. Did you use Android studio and JAVA programming? The home position is basically your first line of code, setting the servos to a start position?
So, the arduino uses C++. I have very little knowledge when it comes to programming. I found 80% of the code needed in a youtube video demonstrating servo functionality with buttons. From there, I had to add a few lines saying "if servo_x is past 120*, then stop".

I do not fully understand how RC servos work. However, their position can be read from the arduino, and when they receive power and are connected to the arduino / control signal source, they auto home to 90*. I have no code written for setting the home position.
We never got into the coding as much as my son wanted, the fellow leading the group found it easier to program himself, and we usually concentrated on the robot engineering to accomplish whatever that years challenge tasks were. Nice work, let us know how it holds up after you're back on the road please. I drove one year without much heat before deciding to clean/service/repair my system, it works much better now. I was going to link that discussion but I had a lot of photos that have been blurred by the "Photobucket Plague". If I can find the time, I will see if I can get away from the links and clean that thread up.

Chris
I'm hoping the servos stay in place. I'm not happy with how I have them mounted, but seem to be doing okay. However, only time will tell....

As for the photo bucket images, download the pictures, upload them to imgur, and replace the links in your article. It'll be time consuming, but itll be worth the effort. Orrrr, you could upload the pictures directly to the site, but I belive there is an 8mb per image limit, and non-users won't be able to view the pictures.
1988 DLX Tercel Wagon w/ weber (RIP)
1985 4wd Tercel SR5 (RIP)
1981 Toyota Tercel

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