PWM - Single Wire

Projects General Guidance
1

Hi. I'm working on a project that requires me to power a motor at variable speeds (one direction only). I'm using an H-Bridge, but am having an issue with the PWM.

The motor is already installed in a vehicle and only seems to have 1 wire coming out of it. (I'm guessing it might have an internal ground to the frame?) So I tried hooking up a single-wire from the H-Bridge to the motor - and it works fine. But as soon as I connect my PWM wire, it stops.

I've copied and pasted code from another motor that I have working, so I know my code works.

My question is: Does something about the PMW require a 2 wire setup? Is there a reason that my single wire setup works fine without the PWM, but then fails with the PWM?

Thanks in advance.

2

With a bridge driver the motor shouldn't have a ground connection.

Look for a "high side MOSFET driver" schematic. (It's easier to control the "low" ground side but that's not an option for you.)

3

No.

Well you are using an unnecessary H-Bridge.
What in the motor driver are you using to apply your PWM signal to?

4

The motor can be driven by a MOSFET.

If the motor is internally connected to 0V and let’s say +12v on the single wire is needed, you will need a HIGH side switch.

Circuit F1 or H1 should work:

5

I'm using the H-Bridge/Motor Driver below.

https://www.amazon.ca/Controller-Dual-Channel-Bridge-Driver-Module/dp/B07D2948RZ?ref_=ast_sto_dp

The reason that I'm using it is because it can control 2 motors - and I'm already driving another motor off one side. So it's there and I thought it would be easy for me to use the other side to drive this 2nd motor.

To your question: "What in the motor driver are you using to apply your PWM signal to?", I have the following connections:

  • Driver Board (Signal Wire Side) Ground to Arduino Ground
  • Driver Board (Signal Wire Side) In1 to Arduino Digital Port.
  • Driver Board (Signal Wire Side) En to Arduino Analog Port.
  • Motor Side, I just hooked one side up to my one motor wire.

My code sends a digitalWrite HIGH to the In1 and an analogWrite (250 for testing) to the En port.

So I realize that I didn't need the H-Bridge, I just thought that it would work - and I can't understand why it doesn't.

Thanks

6

That link says:-

  1. Input PWM duty cycle cannot be more than 98%, or the board won't work stably or even be damaged.
  2. Select PWM frequency according to load type, please use recommended frequency.

So what are you doing in your code to meet these two requirements?
It looks like 250 is just on the limit of the maximum PWM percentage. I would take it down a few notches at least.

The big problem is that the type of chip in that board is unknown so you don't know how it behaves inside.
Are you using a PWM capable digital pin for generating PWM.

Best if you post your code and a schematic, that will answer all the questions.

7

Hi,
Can you please post a schematic of your project, including the motor and power supply connections?

Thanks.. Tom.. :smiley: :+1: :coffee: :australia:

8

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