GM, DR44 2 pin pwm alternator control *Success

[nathaninwa]

Started new thread for my install

Just installed the pwm alternator and freed up pwm3 output and digital freq 3 input

Tested not hooked up and it charges at 13.6 till the fan turns on and then charges at 13.4

I hooked up the pwm to the L and freq 3 input to F I can see in the alternator duty guage it ramp up but nothing changes. I was able to use my DVM and get around 2Volts measure from the pwm output (I undersand that its pulsed 5V and 2 volts will be normal)

Does this pwm wire need a 5V pullup?

Ive tried normal and inverted on the output and inputs

attached is tune and log

[nathaninwa]

More I think about this it seams like I need a pull up resistor to make this a 5 volt setup and run inverted. Would it be the 390ohm resistor as talked about briefly in the manual?

[nathaninwa]

I found a 390, 470 and 1000 ohm resistors. Would one be better to try over the others?

[slow_hemi6]

Is the pullup to Vcc? if so the higher the resistance the less current the circuit will steal from the Vcc supply. But depending on what the impedance is of the circuit inside the alternator too much resistance in the pullup might cause the High you are sourcing through the pullup to be too low for the alternators internal detction circuit. If it forms a resistor divider situation.
So it is a reliable switching Vs Vcc loading situation. If it were me I would probably start with the 1k and see if it worked well.

[nathaninwa]

The dr44 requires a 0-5v pwm signal at 128hz, with 5% being like 10v output and 90% being 15.5v iirc. I tried just the pwm from the ms3pro, but it reads it's looking for positive voltage, so I'd tie into the 5v ref supply and invert the pwm signal

[slow_hemi6]

Ok so 1k limits the load the circuit can draw on the Vcc supply to 5mA, 470r limits to 10.6mA and 390 limits to 12.8mA. I can't remember if the 5v reg is the 500mA part or the 1A part but you do have to be conservative when adding stuff to the Vcc.

[nathaninwa]

The nice thing is, I have a micro running my transmission and since its all canbus'd I have a free 5v supply that's currently only powering two pull-ups on logging temp sensors with a 2490 bias resistor

[nathaninwa]

And PWM success. Adding a 1k resistor as a 5v pull-up got it charging. I may step down to the 470 and test as the commanded DC does not match the voltage, it's low by about a half volt

This has me thinking now, can I use Closed-loop field control with this setup? I'm just wondering as the alternator heats up if voltage may drop and leaving it open loop won't correct for that

[nathaninwa]

I got to thinking this morning, and I could use the generic PID tables for closed loop alternator control. I'm modifying my fuel cell at the moment, so first I'll see how this setup does with open loop, but would be neat to have closed loop