Help designing a "simple" PWM controller

[Piratetip]

Calling electronic gurus on the board that can help me design a circuit or modify an existing controller for PWM solenoid control.

Long and Short:
Manually control a 12v Solenoid in the transmission used to regulate pressure.
PWM from 0-100%

Problem:
Vehicle is too sluggish to fully apply/never fully applies

I have measured all aspects of the circuit that I would like to mimic.
2 wire solenoid, + comes from TCU, - grounded internally inside transmission
Driven by 12V PWM signal at a constant 50Hz
Solenoid 12.6 ohms

Typical operation:
V, A & PWM on time %
P - 0V 0A 0%
R - 3.6V 0.25A 42%
N - 0V 0A 0%
D - 3.6V 0.25A 42%
3 - 3.6V 0.25A 42%
2 - 3.6V 0.25A 42%
1 - 5.3V 0.38A 55%

Full lock up would draw 0.95A @ 100%

I do not have an oscilloscope so I would expect the voltages to actually be 12V, since my multimeter is just averaging the pulses.

The plan is to wire a switch to toggle between normal operation and manual control. Manual control will only be used under certain circumstances for short periods to achieve full or close to full lock up. A dummy load would be used during manual switch over to convince the TCU it is still in control of the Solenoid.

Another problem is that it would have to use a high side driver since there is no access to the ground wire on the solenoid.

On another board I found someone that was tackling the same issue but never finished.
Here is a circuit that was proposed.

As he explained it the fan should be the solenoid and transistor should be MOSFET (IRF630B). I believe he was designing it for a 17 ohm solenoid, so that could be an issue as mine is 12.6.
I am not an electrical engineer so I am a little lost in the construction of this circuit.

Anyone know of any off the shelf units that could work or be modified to work?
http://store.qkits.com/moreinfo.cfm/MX033
I saw this one but the Hz is off and requires both the solenoid + and -, which I don't have access too.

Any help would be appreciated.
:1zhelp:

 

[Piratetip]

Ended up building my own from scratch.
Works perfectly, exactly mimics the TCM control of the solenoid.

Used an Arduino and high side control circuit I built.
Everything is controlled using 1 knob, very simple.
The back end is not so simple but that's the beauty of it.

 

[Kai]

Ooooh. I don't suppose you want to join the transmission controller project?

http://www.supramania.com/forums/showthread.php?122950-Toyota-A-Series-Transmission-controller

We've figured out most of the control hardware, but the PWM control for the solenoid would save us a lot of work. We're using a Xilinx Spartan FPGA as the basis, with full software control of shift points.

 

[Piratetip]

:icon_bigg Possibly
It looks like you have most of it sorted out.

What are you trying to figure out for the PWM control?
I used a Timer function for the ATmega328P controller in the Ruggeduino I used.
This allowed me to set a fixed 50Hz (20,000μs) frequency and I used a potentiometer to set my desired duty cycle %.
But I could set the timer for anything from 1 microsecond to 1,000,000 microseconds.
I built a high side driver circuit to handle power delivery to the solenoid.
Although that Siemens chip you found might be a better solution for how many you are controlling.

 

[Piratetip]

Wow has it been that long since my last post here.
Time really has flown by.

Going to have to start a new thread soon.
Moving back home to the midwest soon, new prospects.
Hoping to pull the Supra out of its 3+ yr storage and start down the list of needed repairs/upgrades.
Starting to miss that car....

 

[Piratetip]

Logged into MKIII tech today since....make a guess.
Even remembered my password on the first time, amazing!

Hall of shame

Starting to get impatient, wanting to work on the old 87' MKIII now!