# Simple Multidirection DC Motor Control

#### sgr9226

Joined Dec 22, 2020
2
Hi Everyone,

I am extremely green to the electronics world, and as such I am looking for direction on a new project.

I need to drive a DC motor clockwise 45 degrees, then counterclockwise 45 degrees repeatedly for a period of approximately 3 seconds, then dwell for 3 seconds, then repeat. I'd like to use a 6 or 9V power supply and the motor run sequence should simply be controlled by an on/off switch. Motor speed must run at approximately 200RPM.

What would be the simplest/cheapest method for controlling this motion sequence?

Are there any concerns regarding motor longevity?

#### shortbus

Joined Sep 30, 2009
9,949
The first part of your requirement is pretty easy, just use a RC servo motor. But the second part the RPM requirement makes no sense. What exactly does a 200 RPM have to do with moving 45 degrees?

Link to RC servo understanding; http://www-cdr.stanford.edu/dynamic/servo/

Joined Jul 18, 2013
27,666
You may be better off with a stepper motor, a typical application.
Max.

#### LowQCab

Joined Nov 6, 2012
3,458
What are you trying to do ????
Is this a Top-Secret Military Project ????
Sounds like you need a Windshield Wiper Motor.

#### Ian0

Joined Aug 7, 2020
8,425
What exactly does a 200 RPM have to do with moving 45 degrees?
It means that 45 degrees takes 37.5ms. So how can it take 3 seconds? Unless you mean a 200 rpm motor with a 80:1 gearbox?

You may be better off with a stepper motor
Or you'd need a pair of limit switches.

#### shortbus

Joined Sep 30, 2009
9,949
It means that 45 degrees takes 37.5ms. So how can it take 3 seconds? Unless you mean a 200 rpm motor with a 80:1 gearbox?
The requirement wasn't mine but was the thread starters, who seems to be missing in action.

#### Ian0

Joined Aug 7, 2020
8,425
The requirement wasn't mine but was the thread starters, who seems to be missing in action.
Apologies. Although I knew that I should have written “unless the TS means. . . “

#### sgr9226

Joined Dec 22, 2020
2
I'm looking to cycle the motor back and forth for a duration of 3 seconds. Assuming the motor starts at a position I'll call 0°, one cycle constitutes travel CW to +45°, then CCW to -45° (90° of travel), then CW back to 0° (45° of travel) for a cumulative angular motion of 180°. At a rotational speed of 200rpm, assuming no delays between CW/CCW motion, with 3 seconds of cycling, the motor will perform "one cycle" of cumulative 180° motion 20 times.

Sounds like a RC servo motor would be a reasonable fit for this application?

#### Ian0

Joined Aug 7, 2020
8,425
Sounds like a RC servo motor would be a reasonable fit for this application?
It depend on how long you want it to keep doing this. A RC servo motor has a run time before failure of 500 hours.

A 1.8 degree stepper motor doing 25 steps forward and 25 steps back could run (almost) for ever.

#### shortbus

Joined Sep 30, 2009
9,949
At a rotational speed of 200rpm, assuming no delays between CW/CCW motion,
Again why is the 200RPM so important? Maybe telling us what you are moving will get better answers.

Sounds like a RC servo motor would be a reasonable fit for this application?
What I said in my first post.

Joined Jul 18, 2013
27,666
For that small of a movement and speed, you most likely could get away without a sophisticated stepper drive, just a switching device transistor/Mosfet using a fixed plate voltage of the motor.
At the desired No. of step counts.
Max.

Joined Jul 18, 2013
27,666
Here is using the cheap L298 board, with Bipolar stepper motor.
Max.

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#### shortbus

Joined Sep 30, 2009
9,949