pwm signal override

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KeithWalker

Joined Jul 10, 2017
3,063
If that is a 12 volt servo and not a 12V DC motor, then the power MOSFET is not needed and the wiring will be different!
Ets23, can you please give us information on what exactly the "motor" is?
 

LesJones

Joined Jan 8, 2017
4,174
This thread is getting more confusing. In post #17 the TS implies that the motor is driving the exhaust valves. I have heard that some modern engines control the valve timing but I assumed they would still driven from the camshaft. I imagined that they may a slack on the cam belt (Or chain.) and tension rollers could be moved so that length of belt on the tension side could be changed.
I have never heard of the valves being driven by motors.

Les.
 

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ets23

Joined Jan 26, 2021
29
Thanks everyone for replying. LesJones it's not the engine valves but the exhaust valves, they are valves to control the noise of the exhaust. They close it to make less noise, in some cars you can manually open them from inside the car in others like mine you cannot control them but the engine opens them when needed. I want to control them to be always open when I want.
This is the actuator
It has 3 wires: a pwm signal to open and close it and then +12v and gnd
 

LesJones

Joined Jan 8, 2017
4,174
A bit off topic but that valve looks very similar to one I made to control the airflow to the oil burner on my furnace for melting metal.
IMG_1101.JPGIMG_1105.JPG
I did use a model servo to drive it.

Les.
 

Thread Starter

ets23

Joined Jan 26, 2021
29
It would be nice but I need to control the already existing actuator in order to keep also the default behavior of the car :)
 

LesJones

Joined Jan 8, 2017
4,174
I suggest starting by driving it using the Arduino and the mosfet board. You will have to try different value pull up resistors as we have no information to base calculations on. It looks like the actuator part is easy to remove so that you can work on it away from the car.

Les.
 

LesJones

Joined Jan 8, 2017
4,174
Another thought. It might be easier to use an NE555 to generate the PWM as it could work directly on 12 volts and MAY be capable of driving the actuator directly.

Les.
 

Thread Starter

ets23

Joined Jan 26, 2021
29
i'm sure it's a 12v signal because other similar project are using a 12v signal. For example you can check this one this one he's doing the same but he doesn't care about the signal coming from the car only opening and closing it with a button
 

LesJones

Joined Jan 8, 2017
4,174
Keith, From what I can see about the mosfet driver the motor out + is connected directly to the + 12 volt supply to the mosfet driver. The motor out - is connected to the mosfet drain. This would work if it was driving a simple motor but the way it is connected in post #35 the PWM input to the motor is held at +12 volts. The PWM output from the mosfet module is applied to the motor negative. This is not the way this motor is expected to be driven. I think the motor out - from the mosfet module should go to the PWM input on the motor. It may also need a pull up resistor as the mosfet can only pull the output towards negative.

Les.
 

KeithWalker

Joined Jul 10, 2017
3,063
You could be right. I don't have a MOSFET module and there is very limited information available. What there is is a very bad translation of the Chinese application note. I guess Ets23 is going to have to take a close look at his unit and decide which way it should be connected.

I have had a closer look at the picture of the MOSFET module and the spec sheet of the IRS540. The way I have it drawn is correct. The MOSFET module input is connected through the relay to the PWM signal from either the Arduino or the computer. The output of the MOSFET module will be a 12V PWM to drive the input of the motor unit. You are correct, a pull-up resistor may be needed across the MOSFET module motor terminals, if there is not one in the PWM input circuit on the motor unit.
 
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LesJones

Joined Jan 8, 2017
4,174
I looked at information on exhaust actuators in general and it seems to be almost identical to the model servo's with a pulse width of about 0.5 mS for one end of the travel and 2.5 mS at the other end of the travel. The pulse amplitude is different from model servo's. There was one website that shows what seems to be the the same mosfet board driving a similar exhaust servo with no pull up resistor so it might work without one. It would help if the TS traced out the schematic of the relay module and mosfet module or at least a picture of the etch side of the modules.

Les.
 

Thread Starter

ets23

Joined Jan 26, 2021
29
Thank you both for the support. Unfortunately I had to buy a new mosfet board because the other one got burned by wiring it the same way in post #35 (I hope I made some mistakes in wiring it because it looks correct to me). Now i've purchased this one because I couldn't find the one I had before. Also attached a picture of the relay
 

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LesJones

Joined Jan 8, 2017
4,174
This is the schematic of the new mosfet board.
310121.jpgIt does not have a back EMF protection diode or optical isolation between input and output which the original one did.
I don't think the middle pin marked VCC is connected to anything.
I think there is a good chance that the only thing wrong with the old mosfet module is the diode. This is not required if you are just using it to drive the PWM pin on the actuator. Just remove the diode by cutting it's wires.

Les
 
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