Hey, I am trying to use arudino nano and FQP30N06L MOSFETs with 4x 5v 200-400 mA DC motor. I power them with 7.2V battery, so i calculated, that the max analogWrite value to get 5V is 178. When I set 178 on pwm pins, the voltage on motors is 7.2V. It also happens with lower pwm signal, but for example 40 works fine.
PWM is a rectangular waveform where you vary the duty cycle.
The waveform goes from 0 to 5v, not anything in between.
Of course if you are keying a driver transistor, the load supply will be the voltage range.
Please read up on PWM.
What is the question?
The question is, why is it happening and how to fix it.
Read up on PWM and if that does not clear up your confusion, get back to us with a better explanation of the problem.
Always show us a good schematic of your proposed circuit.
Show us a good image of your ‘actual’ wiring.
Give links to components.
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So I have a circuit like this.
The PWM signal size is output of potentitometer from the radio transmitter. As soon as the received value from the radio transmitter is PWM > 30 (potentiometer output is 30) the voltage on the motor is higher than 5V. My goal is to have as large a scale as possible to control the drain voltage(that means, that if I mapped the potentiometer on 0, 100 I want to use all 100 to control, not just 30), but the drain must be 0-5v. I hope I explained it better now.
the drain must be 0-5v
Then use a 5V motor power supply. You do not understand PWM.
Motor speed is not a simple, linear function of PWM value, no matter how you implement the control. The motor will not start turning at very low values of PWM.
Please spend some time studying this article: Characterizing a DC motor
The Drain to Source voltage in your circuit will be 0V to 7.2V
If you are using a DMM to measure the voltage, you have equipment limitation.
Only an oscilloscope will show you what is actually there.
okay, I will take a look.
okay, thanks
So I decided to add a L7805CV to have 5V on motors. After that every motor (used separately) stopped around PWM value 30(duty cycle is +- 10%), MOSFETs closed and arduino started blinking and motor started doing "click" sounds. The PWM frequency has not changed. There is a picture of oscilloscope clossest before the situation I describe.
I checked voltages on stabilizator and also on battery, when that happens and they are fine.
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