HVAC louver controller

Hello everyone. I have an issue with the air flow in my house where the upstairs gets much hotter than the main floor. I have a manual louver in the basement I can move throughout the day to make sure the upstairs doesn't get too hot while making sure the main floor isn't too cold. I thought it would be nice to have an automated solution that can handle moving the louver throughout the day based on the temperatures in the house. The temperature sensors I have are nest temperature sensors. Does anyone know where I can start with a project like this? Besides needing an arduino and a high-ish torque servo, I'm not what I need to complete this project.

If you need to keep track of time of day you will want a Real Time Clock like the popular DS3231 or a network connection. Most Arduino boards are not great timekeepers.

For temperature sensors the DS18B20 devices are good. You can hang many on 3 wires, they are identified by address.

The servo will need a power supply capable of handling the servo's stall current (consult the servo datasheet). Arduinos are not power supplies. Despite what you may see on the Internet, an Arduino will not power a servo that is doing anything useful.

Please tell us about moving the louvers. Are you doing this all open or all closed or progressively open and close them? How much force is required? Measure with a spring scale. Are you pushing/pulling or rotating something to make them move?
How far is the movement from open to close?
Do you have space and a sturdy way to firmly mount a motor/servo?
Do you have a convenient mains power source for the power supply?

Here is a picture of the manual handle for closing and opening the louver. It has about 50 degrees of freedom. I don't have a spring scale to determine how much force it needs but it is a decent amount for a servo. I'll most likely mount the board under the handle. There is an outlet nearby. I'll also put the servo over the square piece at the turning point of the handle as that will be the easiest place to spin the handle with a servo.

I'll have a couple angles that I'll have the logic choose from depending on the temperature detected.

So the board will most likely not be anywhere near the temperature sensors. I was hoping I'd be able to get the temperature from my nest temperature sensor but I'm not sure their API provides that data. Shoet of scraping the webui I'm not sure how to grab that sensor temperature.

From the picture, you not only need to move the louvers, you ALSO need to hold them in place. That means continuing power to your servo.

I haven't had the louver handle move on its own or anything like that. It should be fine to just move the servo to a given angle and then be done with it just as long as the servo doesn't revert its angle. The servos I've messed with in the past don't do that.

It looks like you could use a linear actuator or servo of appropriate power here, give it a google - it might simplify the mechanical part of the project.


Are you saying there is a servo or linear actuator I can use without an arduino to tell it what to do?

No, you would still need be able to use an Arduino as the controller. Heaven forbid we engineer that out of your solution!

I just meant that a linear action applied at the end of the existing handle might be easier.

I can't seem to google a picture of what I mean, but the plan to

put the servo over the square piece at the turning point of the handle

is gonna require huge torque compared to moving the handle from the end.

Think of how a piston engages a crankshaft. If you can't imagine it up, I'll try to sketch it.

But I really should stick to things I know anything about - I just always wanted an excuse to even think about the linear servos and actuators you see around, not all of them spendy.


Searh for damper actuators.
Very common.
Small motor high torque.

Slow moving
Stay in place without power

Clamps to damper shaft.
Simple pot feedback.

Made for your application.

Edit add

In addition that blade is balanced in the airflow
Both sides get pushed almost equally so light pressures will hold it in place

Like this one?

I'm not sure how this would be powered and how it would know when to open/close the damper. But it does look like I want in general.

It doesn’t. You still get to put a controller that does “know” into your project; a little microprocessor will be very happy to serve.


Temperature sensor in one zone.
Temp Sensor in other zone.
Whchever is hotter gets more air.

Arduino gets readings and makes the control decisions

Looks like the actuator does not mo e when no power is applied.
When you apply 24VAC power to one terminal it rotates CW
When you apply 24VAC to the other wire it rotates CCW

A simple pot can offer feedback