Hi to all.
I need a positive PWM wave to control battery charger of an electric vehicle.
I've bought this.
the problem is that the positive is permanent and the negative follows the frequency and duty cycles that i choose.
i would like that the PWM will be on the positive.

 

So, you are saying it switches on the low side. common for most commercial PWM modules.

You need to add a P-channel MOSFET to the output, along with a pull up resistor.

 

yes, please do you have any idea about the connection scheme?

 

Gate to PWM output (possibly thru 10 ohm resistor)
Source to positive
Drain is new output.
Pullup resistor is from positive to gate.

Use a good logic level PMOS.
Resistor values I usually determine with testing.
I would start with 10k pullup, and 10 ohm gate resistor.

 

you mena something like te blue circle? right?

 

Correct

 

I only mentioned a logic level MOSFET because that module can work down to 3.3 you may not actually need one depending on the voltage you are going to use.

 

I only mentioned a logic level MOSFET because that module can work down to 3.3 you may not actually need one depending on the voltage you are going to use.

excuse me @ElectricSpidey, my English isn't good but even translating it with google I didn't understand what you are meaning. Please can you express the same concept with other words? In this case I need to supply the module with 12vdc. That because I need an PWM 12v, 300hz.
I dont know how many mA I can inject and how can I limit the amperage.

 

Can you tell Mr. ElectricSpidey how many volts is used to power your Arduino?

 

oh no, I take the pic only like an example... I must use the board I mentioned on the first post.
Because i need to change the duty-cycle often.

 

Hi to all.
I need a positive PWM wave to control battery charger of an electric vehicle.
I've bought this.
the problem is that the positive is permanent and the negative follows the frequency and duty cycles that i choose.
i would like that the PWM will be on the positive.

Okay on the back of the pcb, there is a transistor with a 100R pull up resistor R2 to positive to provide the pwm output which is Negative side, but the small resistor R1 is the Positive pwm feed to the transistor, you could use this feed to your Mosfet..

 

may I use this mosfet this way like the pic?

 

Use a N-fet and put it in a Source follower mode, that way you will be getting the positive pwm output, .

What voltage is the motor using?

 

you mean this way?

 

Use a N-fet and put it in a Source follower mode, that way you will be getting the positive pwm output, .

I don’t think so. A source follower does not invert.

 

Like this..

 

I don’t think so. A source follower does not invert.

If he takes the output directly from the R1 it's already positive, so he can just buffer it, the pcb gives an open collector output to positive via R2 resistor.

 

now is correct?

 

now is correct?

Yes but without the 10K resistor, you may need to use two MOSFETs as the pwm signal will probably be only 3V ..

 

The MOSFET in post # 12 should work just fine.

It is your choice to try and solder a wire to a board where no wire is supposed to be soldered, risking damage to the board.

What does it accomplish...saving a resistor...I don't get it.

There are other issues as well, but I'm not into debating "experts".

But the choice is yours.