Question about circuit design -- 24v dc brushed motor to control force feedback...

Thread Starter

siris

Joined Nov 2, 2013
5
Hello all,
Long story short, I have a project in mind and not sure how to get there, hoping to get some insight or advice.

I have a sim racing setup with a steering wheel that's getting long in the tooth and I'm trying to get a little more mileage, pardon the pun, out of it.

The problem is the wheel uses a 24v dc brushed motor to control force feedback and it will not return the wheel to center fast enough to correct an oversteer situation. I would like to give it more voltage to get more rpm out of the wheel. Clear as mud? Everyone still here?

My thoughts are to provide a separate power supply, probably an adjustable 0-46VDC to dial in max wheel speed, intercept the existing power leads to the force feedback motor and use them to regulate the new power supply to the motor. I do not know at this point how the SIM wheel provides voltage to the force feedback motor, pulse width or variable voltage. I am familiar with Arduino's and c++ so I could build an Arduino to read the wheels intended voltage and apply voltage from my new power supply. But I was wondering if it's possible to just wire in a pair of transistors or MOSFETs and a couple flyback diodes to control the motor.

Any help is appreciated, and if any of my rambling has been incoherent I can try to explain better.
 

MrSalts

Joined Apr 2, 2020
2,387
Hello all,
Long story short, I have a project in mind and not sure how to get there, hoping to get some insight or advice.

I have a sim racing setup with a steering wheel that's getting long in the tooth and I'm trying to get a little more mileage, pardon the pun, out of it.

The problem is the wheel uses a 24v dc brushed motor to control force feedback and it will not return the wheel to center fast enough to correct an oversteer situation. I would like to give it more voltage to get more rpm out of the wheel. Clear as mud? Everyone still here?

My thoughts are to provide a separate power supply, probably an adjustable 0-46VDC to dial in max wheel speed, intercept the existing power leads to the force feedback motor and use them to regulate the new power supply to the motor. I do not know at this point how the SIM wheel provides voltage to the force feedback motor, pulse width or variable voltage. I am familiar with Arduino's and c++ so I could build an Arduino to read the wheels intended voltage and apply voltage from my new power supply. But I was wondering if it's possible to just wire in a pair of transistors or MOSFETs and a couple flyback diodes to control the motor for left and right turn feedback.
Any help is appreciated, and if any of my rambling has been incoherent I can try to explain better.
You have some possible issues ahead of yourself that may not be a problem.
First, you need to know that your brushed DC motor is run in both directions to get your left snd right turn. This reversible circuitry is often achieved with an H-bridge of four transistors plus (possibly) a fifth transistor for PWM control at the bottom of the H. The transistors used to make the H-bridge may be big enough and handle the voltage of your 46v supply. The control is all on the low voltage side so even the P-channel Mosfets on the high side are triggered by the cpu or microcontroller at logic level voltages. Open it up and let us know what the first two pair of transistors you see connecting to the power wires for the motor. Post the part numbers. And post a photo so we can see what that section of the board looks like.

Also, it may be completely possible that the code and software are the problem and the same response will be felt with any voltage.

Assuming the software isn't the problem, Another option is to use a motor with a smaller diameter but longer axis. This type of motor will have less rotational inertia and be able to flip directions quicker.
 
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Thread Starter

siris

Joined Nov 2, 2013
5
You have some possible issues ahead of yourself that may not be a problem.
First, you need to know that your brushless DC motor is run in both directions to get your left snd right turn. This reversible circuitry is often achieved with an H-bridge of four transistors plus (possibly) a fifth transistor for PWM control at the bottom of the H. The transistors used to make the H-bridge may be big enough and handle the voltage of your 46v supply. The control is all on the low voltage side so even the P-channel Mosfets on the high side are triggered by the cpu or microcontroller at logic level voltages. Open it up and let us know what the first two pair of transistors you see connecting to the power wires for the motor. Post the part numbers. And post a photo so we can see what that section of the board looks like.
From my understanding it is a brushed dc motor.
 

Thread Starter

siris

Joined Nov 2, 2013
5
Yup, those are controlled by the H-bridge circuit as described.
Ok, sorry your first reply said brushless, I just wanted to clarify. It's a bit of a chore to disassemble the SIM rig to pull the wheel apart but I'll work on that tomorrow. If I'm understanding right you think if I can isolate the existing MOSFETs I should be able to feed them from the stand alone power supply. I was wondering that myself but wasn't sure I would be able to divorce them from the PCB, which is why I was interested in a stand alone circuit. I'll update this post with pictures when I get some free time to tear down the wheel. Thank you for your time and replies.
 

MrSalts

Joined Apr 2, 2020
2,387
Ok, sorry your first reply said brushless, I just wanted to clarify. It's a bit of a chore to disassemble the SIM rig to pull the wheel apart but I'll work on that tomorrow. If I'm understanding right you think if I can isolate the existing MOSFETs I should be able to feed them from the stand alone power supply. I was wondering that myself but wasn't sure I would be able to divorce them from the PCB, which is why I was interested in a stand alone circuit. I'll update this post with pictures when I get some free time to tear down the wheel. Thank you for your time and replies.
My mistake ( some here would call it a "typo" but it was my brain slip). Yes, brushed DC used an H-Bridge circuit to control a reversible brushed Dc motor. Corrected above.
 

MrSalts

Joined Apr 2, 2020
2,387
Also, if it's a pain to pull apart, you need to balance the effort with the possible reward. Make your own decisions - I assumed it was pulled apart already.
 
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