# Controlling an electric motor using strain gauges

Hello,
This is my first foray into Arduino and am not sure I can accomplish my goals.

I know I can control a e-bike controller using an Arduino and a potentiometer. I would guess i could also use the voltage output from a wheatstone bridge with a strain gauge in place of the potentiometer.

I am looking to take this one step further though. I would like to have the motor driven so that the reading from the strain gauge does not exceed a pre determined value. Imagine a wagon with a strain gauge mounted to the pull handle. If I pull this wagon by the handle a strain will be measured. As i pull harder the strain will increase. Once the strain reaches a certain level the motor will engage to keep the strain from exceeding that value.

Is it possible to accomplish this using an arduino or will I need to connect a computer of some sort to handle it?

Hopefully I provided clear information as to my intent. I apologize if I sound like a noob, I very much am

What does the strain gauge measure?

it measures the strain on the pull handle. As the metal stretches the gauge stretches with it which changes the resistance. This is then converted to voltage through a Wheatstone bridge and amplified and scaled between 1-10 volts. I would want the measurement to stabilize around x volts.

crazy_pyro:
it measures the strain on the pull handle. As the metal stretches the gauge stretches with it which changes the resistance. This is then converted to voltage through a Wheatstone bridge and amplified and scaled between 1-10 volts. I would want the measurement to stabilize around x volts.

Your Arduino did not get a voltage from the potentiometer. It gave you a number between 0 and 1023. You did something with that number. A strain gauge and anplifier will also give you a number between 0 and 1023. Or perhaps a smaller range. It is up to you to determine what you want those numbers mean and what you want to do with them. Forget the VOLTS.
Paul

crazy_pyro:
Is it possible to accomplish this using an arduino or will I need to connect a computer of some sort to handle it?

Yup quite easily possible.
Although you are not that clear but what I have got is you want to design a PID controller. You want to control the strain guage value using motor or the vice versa. Anyways in both cases it won't be that difficult, first of all read the sensor's value and display it on Serial Terminal of Arduino.
After that manually control your output (electric motor or guage) and then simply join both codes i.e. getting data from sensors and then controlling output. and yeah you can do this go for it

I'm unsure whether what you want is to measure the pull force delivered by the motor or to control the motor with some sort of pull handle. Can you post a drawing of your idea?

Hi,
Welcome to the forum.

Please read the post at the start of any forum , entitled "How to use this Forum".
OR

I think the op wants to be able to pull a trolley, the trolley is motorised,
As he/she pulls the trolley, motor engages to keep up with the operator.

Using a strain gauge in the pull handle to measure the force/strain as the pullee pulls.
When the force/strain increases to a threshold the motor is engaged and then using the live force/strain measurements the controller keeps a near constant pull force while the pullee continues to walk infront of the trolley.

As suggested PID may be needed to compensate for the different loads/speeds on the trolley giving different values of inertia/momentum.

Tom...

TomGeorge:
Hi,
Welcome to the forum.

Please read the post at the start of any forum , entitled "How to use this Forum".
OR
https://forum.arduino.cc/index.php?topic=712198.0

I think the op wants to be able to pull a trolley, the trolley is motorised,
As he/she pulls the trolley, motor engages to keep up with the operator.

Using a strain gauge in the pull handle to measure the force/strain as the pullee pulls.
When the force/strain increases to a threshold the motor is engaged and then using the live force/strain measurements the controller keeps a near constant pull force while the pullee continues to walk infront of the trolley.

As suggested PID may be needed to compensate for the different loads/speeds on the trolley giving different values of inertia/momentum.

Tom...

Yes! I just received my first arduino board today and will begin learning the ropes. I appreciate the confirmation that I'm not barking up the wrong tree. Everybody here has already been very helpful. Thank you all!!!

I'll be back with more educated questions in the future as I do my best to break things

Kyle

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