What motor and motor shield do I need?

Hello everyone! This is my first post on here and I'm a fairly new user and experimenter with Arduino. I am attempting to control a little heating unit in my room with a motor and an Arduino.

The heating unit has a dial in which you can turn both ways (open and closed). The dial is fairly easy to turn, but fully closing it takes a little torque. My idea is that I would like to connect a temperature sensor to my Arduino, and have it tell the motor to turn the dial to open when the temp. goes below 70 degrees, and vise versa for when it's above 70 degrees.

As far as I can tell, I need a motor shield and a motor. However, I'm not sure what motor type I need and how powerful it should be. I'm thinking something around 2-5amps? I also don't know what motor shield I would need to get.

Thanks for any and all help! - Isaac

What exactly is this "heating unit" - is it something portable, or is it mounted on a wall or something? Is it electric?

If it is portable and electric - and if you are comfortable and understand mains AC - then likely that knob just controls a simple bimetal thermostatic switch. It probably has only two terminals - one terminal connected to the heating coil (with the other end of the heating coil connected to the neutral side of the AC mains), and the other terminal connected to the "hot" side of the AC mains (there may also be a switch and/or a motor for a fan involved, but likely all of those are in series with each other - though a motor/fan might be in parallel, and/or have a switch to control it).

So - if you wired a simple SPST relay (or a solid state relay) in parallel with the thermostat - then controlled the relay with the Arduino - you could dispense with trying to control the thing with a mechanical solution.

Maybe you could use a servo to turn the knob. They come in a wide range of sizes and are very easy to control with an Arduino.

Servos have all their electronics inside so you don't need a shield. But the servo does need its own power supply - don't try to power it from the Arduino 5v pin.

...R

rolledcoal: The dial is fairly easy to turn, but fully closing it takes a little torque.

The question is how much torque?

Why not measure it?

I like the servo idea. How much does the dial rotate (in degrees) from one extreme to the other?

cr0sh: What exactly is this "heating unit" - is it something portable, or is it mounted on a wall or something? Is it electric?

If it is portable and electric - and if you are comfortable and understand mains AC - then likely that knob just controls a simple bimetal thermostatic switch. It probably has only two terminals - one terminal connected to the heating coil (with the other end of the heating coil connected to the neutral side of the AC mains), and the other terminal connected to the "hot" side of the AC mains (there may also be a switch and/or a motor for a fan involved, but likely all of those are in series with each other - though a motor/fan might be in parallel, and/or have a switch to control it).

So - if you wired a simple SPST relay (or a solid state relay) in parallel with the thermostat - then controlled the relay with the Arduino - you could dispense with trying to control the thing with a mechanical solution.

This heating unit is something mounted to the wall which goes directly to the vents, so unfortunately this solution will not work.

Robin2: Maybe you could use a servo to turn the knob. They come in a wide range of sizes and are very easy to control with an Arduino.

Servos have all their electronics inside so you don't need a shield. But the servo does need its own power supply - don't try to power it from the Arduino 5v pin.

...R

This sounds like a great idea! The servo does not need to turn more than 180 degrees to fully open or close the dial. Do you think you could link me to a servo that provides enough power? Every time I've looked up a servo I only find ones that power themselves off of the Arduino itself. Or at least give me a keyword to search for a motor with an external power supply :)! Also, do I need external power regulators and switching regulators?

Thanks again, Isaac

rolledcoal: This sounds like a great idea! The servo does not need to turn more than 180 degrees to fully open or close the dial. Do you think you could link me to a servo that provides enough power? Every time I've looked up a servo I only find ones that power themselves off of the Arduino itself.

Without knowing the torque required to turn the knob it's hard to know what servo to recommend.

HobbyKing sells all sorts of servos. I like this one. (I used 18 in this hexapod.) Unfortunately this servo doesn't have a full 180 degree range of motion. I think it's safe to say most hobby servos don't have a full 180 degree range. This 9g servo from HobbyKing does have a full 180 degree range but it probably is not strong enough for this application.

There are probably a few micro servos which can be safely powered from an Arduino's 5V rail but in general servos should get there power from a different source than the Arduino's 5V line.

DuaneDegn: Without knowing the torque required to turn the knob it's hard to know what servo to recommend.

HobbyKing sells all sorts of servos. I like this one. (I used 18 in this hexapod.) Unfortunately this servo doesn't have a full 180 degree range of motion. I think it's safe to say most hobby servos don't have a full 180 degree range. This 9g servo from HobbyKing does have a full 180 degree range but it probably is not strong enough for this application.

There are probably a few micro servos which can be safely powered from an Arduino's 5V rail but in general servos should get there power from a different source than the Arduino's 5V line.

Is there an easy way to find the peak amp draw for a servo motor? Say I bought the first motor you linked, it uses 5-7volts but does not list the how many amps it draws. I have found power supplys that can give a constant 5 volts, but the power supply's amps range from 1 to around 8. I'm sure I can find a power supply with more amperage if necessary. Should I just go with the 8 amp, 5 volt and call it good?

Having too many amps is never a problem (except for your wallet), whereas too few will be a problem.

Without knowing which servo you plan to use it is not possible to advise about the number of amps. My blind guess is that 8 amps would give you a comfortable margin unless you have a very large servo.

...R

Robin2: Having too many amps is never a problem (except for your wallet), whereas too few will be a problem.

Without knowing which servo you plan to use it is not possible to advise about the number of amps. My blind guess is that 8 amps would give you a comfortable margin unless you have a very large servo.

...R

Awesome! I think I know what I'm going to get now. Thank you everyone for all the help, much appreciated!

  • Isaac