DC Motor Control from ECU ???
Turbo Mini Forums

the gate resistors can be pretty anything, Fet's dont flow any appreciable current in or out of the gate (normaly nA's) as they work on voltage field. with the values Ive given above, there will be about 1mA flow through the resistors, so about .01W.


as fets dont flow any gate current any static has nowhere to go so can build up until it punches through the silicon and shags the device, so you should electrstatically bond yourself and your iron to gnd when fitting them.

Thanks Joe, I'll use some standard 1/4W resistors.

I'll google bondage to see what I need to do :)

Am I also going to pop the FETs if I test for lack of bridging on the veroboard with my Multimeter?

I've tested the MS3X output on the JimStim using the IAC1 LED. Works fine, dim glow at low duty cycle to full on at 100%. But 100% duty cycle is fully grounded.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Also,

on a circuit that is used in a harsh electromagnetic enviroment like this, I would stick something on the inputs and voltage rails to prevent voltage spikes,

on logic stuff you often see a 5.1v zenner in inputs to sink anything over 5v, the main input to the MS has the MOV and some zeners or about 28v IIRC, something like an 18v zenner on the +ve and input might be a good idea once youve got it working.

We've used somthing called a tranzorb at work, similar to a zenner, but in massive ratings, like 1500W pulse, they also repond very fast so are good for transients.

Joe,

I'm going to have to disagree on the gate current.

A low power FET may be field driven but everything I've read about high power MOSFETs say the gate capacitance is large so the initial gate charge current is measured in Amps, not uA.

Which is (I think) why Jean recommended a very low resistance for the gate drive (and hence it needs to be high power rated).

Just looking at the MS2/3 standard MOSFET drives, which are current limited to 14A, their gate drive resistor is 22ohm.

I may be totally wrong - I'm far more used to bipolar rather than FET - but thinking of gate current in uA for driving 40 - 80A across the device just doesn't seem right.

Schrödinger's cat - so which one am I ???

Bah,

Rods right, ( hate fets BTW lol)

the datasheet calls for 4.7 Ohm, but makes no mention of gate current, only charge... and its been far to long since I dabbled with that!

still needs a pull up IMO so with say 4.7 ohm gate resistiance your looking at 2.7 amps, so about 30 watts... fook me thats a lot, can the MS port support that??

Edited by Paul S on 24th Nov, 2013.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

On 24th Nov, 2013 Paul S said:

On 12th Nov, 2013 jbelanger said:
Paul,

The MS3X PWM outputs are ground switching outputs that can handle more current that a ZTX450 (up to 3A). So you can go back to the previous diagram (actually you'd need a pull up resistor if you wanted to use the NPN transistor with the MS3X outputs).

Jean

EDIT : Not sure that's right. The MS3X uses a IPS022G dual mosfet with a 1A continuous load

Schrödinger's cat - so which one am I ???

What the MS3 schematics says for U1-3 is "IPS022G (or VNS3NV04D)"

A quick look at mine reveals that it is fitted with the VNS3NV04D which are rated for 3.5A :)

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I've sort of got this working, but I think that there is a problem with the motor.

I've bypassed a lot of the issues with the circuitry by using a 80A solid state relay. I appreciate all the help with making my own circuit, but I had to cut my losses. Homebuilt circuits are not my thing.

Anyway, wired it all up with the solid state relay driven by the PWM signal. Nice flashing light on the relay confirmed that it was operating. The motor was just inching round at low duty cycle. But as soon as I turned up the coolant temp on the stim just a tad, it blew the 30A main fuse.

The motor is very stiff to turn. It's just the brushes holding it so I'm going to strip it down and investigate to see if I can free it up.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The motor is furbared, I think.

Ran it on jump leads for a bout a minute. Both motor and leads got hot and smoky :(

Source another motor or give up ?????

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Tried the circuit on a brand new high torque starter with the same motor and blew the fuse before it really got turning.

So, it's a function of the motor design that is the problem

I'll keep an eye out for a tail lift or winch motor, but will they be any different ??????

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."