PWM converter and PWM fuel pump control

[Bevan]

Hi,
I'm trying to implement a PWM fuel pump control with my MS3. I have a pwm converter board to step up the frequency and hopefully keep my pump happier.

I can get my MS3 to put out a PWM signal on the fuel pump wire. I was planning on feeding this signal to a box with the pwm multiplier, some driver Mosfets, and a 5v regulator in it.

Rather than using the on board TIP122 transistor to directly control the pump grounding, I was going to use it's output to drive some IFR4905 P-type Mosfets in parallel. My pump is rather thirsty and can pull up to 30A. Will this work ok?

Also, since I need 5v to the PWM mutiplier board, will it work to simply put a 5v regulator chip in the box and having it feed off the 12v pump input wire?

Bevan

[jbelanger]

Bevan,

You don't want to connect the P-type MOSFET directly to the CPU. You should instead use the TIP122 to drive the MOSFET. Use a 10 to 100 Ohm resistor to connect the MOSFET to the output of the board.

And you can't simply use a 5V regulator. You need to add a few things for protection since the automotive environment is quite harsh. Look at the MS board schematics to get an idea of what should be done.

Jean

[dontz125]

A fellow named Madhu makes a PWM pump controller with a microprocessor that uses a pressure sensor signal as the control input. He and I have been talking about a partnership; to that end I have modified his design with an eye towards making it more robust for an automotive environment. This could easily be uprated to have a pump current design rating of 30A (50 or 60A hardware limit).

[superdavemotorsports]

Bevan,

You don't want to connect the P-type MOSFET directly to the CPU. You should instead use the TIP122 to drive the MOSFET. Use a 10 to 100 Ohm resistor to connect the MOSFET to the output of the board.

And you can't simply use a 5V regulator. You need to add a few things for protection since the automotive environment is quite harsh. Look at the MS board schematics to get an idea of what should be done.

Jean

I am looking to do something similar with a Meziere water pump, max 15A under load. Could you expand a little on this reply, maybe a simple diagram with the TIP122, mosfet and protection components?
Would the current 250hz capabilities of the generic pwm outputs from the ms3x work as a water pump speed control?

[superdavemotorsports]

In ths thread http://www.msextra.com/forums/viewtopic ... 47#p447647 we have come along way towards getting this to work using a simple circuit

[jbelanger]

I've split this thread since the discussion was related to the IOx and that were the posts are now.

Jean