Forward & Reverse of Linear actuator in Greenhouse roof

Forward & Reverse of Linear actuator in Greenhouse roof
The goals are
A. To use a temperature sensor hung in the eve of Greenhouse to open and close the linear actuator on 12V DC.
B. To operate a 14” 12V DC fan from a thermostat hung in the eve.
C. To operate a 12V DC water pump for a humidifier on the South wall.
D. Operate a solar charge system to operate all of the above
A little history-
2014 Reinforced a Harbor Freight 10’ X 12’ greenhouse to grow Orchids here in the High Desert of NV.
Bought a 12V DC -8” stroke linear actuator for opening the ceiling vent, works great with a SPDT switch. Bought these parts and have no idea how to make my goal a reality.

  1. Arduino Uno Rev3 out of the box and still scratching my head with the instructions + R&G colorblind.
  2. Motor Driver Board for Arduino
  3. 12V DC Digital Temperature Controller DC sensor Thermostat Control
  4. DAYTON 5X838M RELAY On suggestion from a different board.
  5. PCB Mounting 12V DC Coil Voltage 4 Pin Power Relay JQX-30F (T93) On suggestion from a different board.
    Not very good with Electrical diagnosis nor power theory, can read a little on schematics, can solder and use a simple digital multimeter and R&G colorblind
    Searched through the blogs and so many I just get confused!

It is quite simple to use an Arduino/motor controller combination with the linear actuator, but we need to know more about both the actuator and the motor controller. Can you post links to the product pages or data sheets of either?

Thank You,
Found a e-bay site that gives the specs for the motor controller -
And one for the linear actuator -

The specs for the actuator don't list the no load running current or the stall current at 12 volts, which you absolutely need to know. The actuator motor will briefly draw the stall current every time it starts, and the motor driver must be able to provide at least close to that.

An actuator capable of 225 pounds force will draw several amperes under load, which the L298 motor driver is not capable of providing. You will probably need a motor driver like this one:

I use that driver to open heavy sliding vents in a green house, with these actuators and am very happy with the performance and reliability. Pololu gives excellent product information, clear instructions and the engineers provide outstanding support for their products.

The page you guided me to is pretty thorough. Before I order this #1451 VNH5019 Motor Driver Carrier what else is needed?

The higher power motor driver should be enough to get started!

You should solder the motor connectors to the board and make sure not to change any wiring when the board is powered up. That can instantly destroy a motor driver.

Got it coming

Hello jremington,
Got the information on the Linear actuator, 0 load draw = .5a, max load draw is 2.5a.
Got the Motor Driver Carrier and really don't see how this fits into what my goal is. The actuator has a built in limiter, all I wish to do is reverse polarity when the temperature changes.

The motor driver carrier drives the motor on the linear actuator. Follow the wiring and other instructions on the Pololu product page very carefully.

At the minimum, the Arduino will read the temperature sensor and then based on that reading, may choose to turn on the motor in the appropriate direction to open or close the vent.

The minimal program could look similar to the following pseudocode, where the setpoints are chosen such that the vent doesn’t open and close with each tiny temperature swing.

void loop() {
int x = read_temperature();
if (x > UPPER_SETPOINT) open_vent();
if (x < LOWER_SETPOINT) close_vent();

The functions read_temperature() etc. will depend on the temperature sensor and how you have chosen to wire everything together.

You probably use two relays like below in a setup like in the attached picture to operate the linear actuator.


Just to close this post. Found a set of 12VDC relays that hook up to a 12V thermostat that opens and closes my Linear Actuator. Way cheaper and easier to operate than all this high tech guru stuff. So thank all that helped and all that kept out iof this.

I would offer that if you get a couple of 5 volt relays, you can run them from the Arduino easily and have more control of the temperature.

if yoiu know it will be night soon, and getting colder, you might want to close the roof to hold in the heat.

ditto for a daytime when it is actually hotter outside and opening them will not make it cooler.

kudos on figuring out that relays are all you need.