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Discussion Starter #1
I've been trying to figure out how the OD2 Electric Limited Slip Differentials work. With the end result of installing them in a non QD2 and using a switch and relay to turn the lockers on and off.
Sounds easy, or simple? I have a ELSD solenoid I'm playing with a simple 12vdc power applied to it doesn't do a thing to the solenoid.
Looking in the service manual, it appears these solenoids are controlled by the Final Drive Control Module and it sends power in the form of PWM (Pulse-width modulation) at a1khz frequency and then applying a 0 to 100% duty cycle.
My question is for all the electrical savey forum members. Can a simple PDM controller running at 1khz, for changing the speed of a DC motor or for changing the intensity of LED lights be used to turn on the solenoid?
I assume a potentiometer would provide adjustment form 0 to 100 load? If so it would be set at 100. A switch could then be used to turn the PWM on and off, and you would end up with a selectable locker.
 

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I have QDII and studied this issue deeply and I made a box with two switches to kill the ELSDs for sand driving, and I wanted to improve it to add manual control and stopped at knowing that it works on PWM signal, although I thought a constant 12V would work since the 100% duty cycle PWM signal is actually a contact signal ,,, see this diagram :




I'm happy and interested that you managed to get hold of the Solenoid for testing, Are you sure you applied the correct polarity?
 

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Discussion Starter #3
I have QDII and studied this issue deeply and I made a box with two switches to kill the ELSDs for sand driving, and I wanted to improve it to add manual control and stopped at knowing that it works on PWM signal, although I thought a constant 12V would work since the 100% duty cycle PWM signal is actually a contact signal ,,, see this diagram :




I'm happy and interested that you managed to get hold of the Solenoid for testing, Are you sure you applied the correct polarity?
Not sure on the polarity, but I tried it both ways. Attached is the wiring diagram from the service manual. Switched Battery Solenoid Supply (Dark Green/Yellow) I believe is (+) and Front Differential Solenoid Control (Dark Green/Dark Blue) I believe is (-) and is turned on and off at 1khz frequency. And like you show the duration of "on" dictates percent of duty from 0 to 100.
And I would have thought 100% duty would be a contact signal as well. but appears not to be. How do voltage and current affect all of this?
 

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What was your 12V source?
 

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Discussion Starter #5 (Edited)
I used an automotive 12vdc battery, a 12vdc power supply and 9vdc battery. Swapping leads on all. I tested the solenoid for the correct resistance before and after, it reads 13.5 ohms, which is in spec per the service manual. The only thing I can think of is a solenoid made for PWM power requires a square wave power source. Is 12vdc the correct voltage, maybe 5?
 

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The automotive 12vdc battery should definitely be valid source and no its not a 5V , its 12V

then it needs a PWM signal ,,,, Are you handy to built a small electronic circuit to do that?
 

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Discussion Starter #7 (Edited)
The automotive 12vdc battery should definitely be valid source and no its not a 5V , its 12V

then it needs a PWM signal ,,,, Are you handy to built a small electronic circuit to do that?
I have been looking for some PWM controllers. I see a lot of them for driving DC motors, computer fans and then some led lights. I would think one of these would work, if the frequency was right for the solenoid. The xk service manual states 1khz for this solenoid, does that sound right? Most of the controllers I can find are 100hz. Also I guess a potentiometer is used to control load duty 0% to 100%?

So far this is the only PWM controller I found that is adjustable to 1khz:
http://www.sparkfun.com/products/9668
 

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I have the same service manual and yes it says 1khz and that looks ok ,, 100Khz is too high for such function. and yes some circuits use potentiometer to play with the duty cycle.

I will also try to look for some simple circuits to do that, its been around 10 years since my last hands on electronic circuits back in collage though :)
 

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Discussion Starter #9
Cool, I'm sure there is a circuit out there to build, I'm a mechanical engineer, so I'm electrically challenged......

I also have an email into this company, maybe another source:
http://www.pololu.com/
 

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This looks super interesting. I am also keen to find a way to lock the centre diff manually on sand/gravel as it adds substantial stability. Please keep us informed.

cheers
 

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Discussion Starter #11 (Edited)
I ordered the following:

http://www.canakit.com/30a-motor-speed-controller-pwm.html

• Supply / Load Voltage: 6 to 24V DC (12V DC Recommended)
• 30 Amps @ 100 Hz Maximum Continuous Current
• Independent controls for Duty Cycle and Frequency
• Fully adjustable from 0 to 100% Duty Cycle
• Frequency: 100Hz or 244 Hz to 3.125 KHz
• PWM Duty Cycle Range: 0% to 100%
• High efficient design using two 110A High-Power MOSFETs
• Includes two Heatsinks

This should should give me enough adjustablity to figure out what the solenoid needs.
 

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I ordered the following:

http://www.canakit.com/30a-motor-speed-controller-pwm.html

• Supply / Load Voltage: 6 to 24V DC (12V DC Recommended)
• 30 Amps @ 100 Hz Maximum Continuous Current
• Independent controls for Duty Cycle and Frequency
• Fully adjustable from 0 to 100% Duty Cycle
• Frequency: 100Hz or 244 Hz to 3.125 KHz
• PWM Duty Cycle Range: 0% to 100%
• High efficient design using two 110A High-Power MOSFETs
• Includes two Heatsinks

This should should give me enough adjustablity to figure out what the solenoid needs.
That looks good,, then you have to run on the variable mode to get the 1khz, but how you will measure when the frequency reached 1khz?
 

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Discussion Starter #13
I have access to a digital multimeter that can read hz and duty cycles to set frequency and load.
I think after I set them and have it all working I could measure the potentiometer resistances. Remove the potentiometers and replace them with the correct resistors to hold frequency and load. I think that's possible?
I don't like the idea of the adjustment after everything is working.
 

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That is perfect ,, I was also worried about the variable mode stability, good you are going to replace with fixed resistor, but you should keep the variable duty cycle at least for testing phase and then fix it.

What about the output voltage level ? ,, is it 12V ? I didnt notice it in the instruction sheet !!

also you need to make sure that its 12V beak to beak
 

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Discussion Starter #15
That is perfect ,, I was also worried about the variable mode stability, good you are going to replace with fixed resistor, but you should keep the variable duty cycle at least for testing phase and then fix it.

What about the output voltage level ? ,, is it 12V ? I didnt notice it in the instruction sheet !!

also you need to make sure that its 12V beak to beak
beak to beak? Not sure what you mean.

The output voltage level will be a factor of the load percentage. 12vdc in, 50% load, 6vdc output, etc. The duration of the "on" part of the duty cycle dictates the output voltage. Basically the PWM is turning the dc power on and off at 1khz frequency, the longer the "on", the higher the output voltage.
 

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Discussion Starter #16 (Edited)
Update, I cancelled my order to Canakit for the Motor Controller PWM. It has a soft start feature. Which for a motor, it's good, but for a solenoid, it probable will not work. The soft start ramps up current and voltage.
A solenoid needs that current to get it to move.

I've ordered this PWM Solenoid controller instead:

http://www.criticalvelocity.com/item.php?itemid=vc5

It's made to control PWM solenoids. The frequency is selectable, 860hz or 1.9khz should work. This driver activates the solenoid with the full supply voltage, and after a configurable delay of 0 to 1 sec, reduces the output
voltage to a configurable level to save power, reduce coil heating, and prolong coil life while keeping the solenoid activated.
This is what I think Jeep is doing out of the Final Drive Control Module. I do not believe this is a proportional solenoid. But if it is, I can still set it at 100% load.

The amperage is also configurable as well. If I use ohms law: Voltage= Amperage * Resistance (V=I*R) and considering the resistance of the solenoid measured at 13.5 ohm with 12 vdc the current it uses is 0.88 amps.
This unit is good for 2 amps.
 

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Discussion Starter #17
Update, As I'm waiting for the PWM controller to come in the mail. I was mistaken about 12 vdc firing the solenoid. It did and it does actuate the valve closed with 12vdc.

Here is my confusion on this. The solenoid must have been closed when I got it. I used a small diameter pin to push on the plunger of the solenoid and it easily retracted into the solenoid. When the plunger is retracted, it opened a path for air (oil) to pass through. So I fired the solenoid with 12 vdc again and the plunger extended and close off the oil path. But releasing the 12vdc does not cause the plunger to retract. I can easily push the plunger to retract with the small pin. Hardly any force at all.

I have never dealt with hydraulic valves and this one is a simple on/off with one path. The pneumatic solenoid valves I am used to, have a spring return when they are a single solenoid. My question is this? It seems as if there is no spring return to this valve, is it possible they designed it to be retracted by the hydraulic pressure of the closed off path? If you think about it, the solenoid holds the path closed until de-energized and then the built up oil pressure pushes the plunger to open the path and release the pressure.

Any thoughts please?
 

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Discussion Starter #18
I can actuated the solenoid with a "triple A" battery (1.5 dc) but still no retract with removing power. I wonder what voltage is 100% lockup? I think the trick here is finding the lowest voltage required for maintaining full locking, which will keep the solenoid heat build up low.
 

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Discussion Starter #19
Testing the Solenoid at 12vdc and 14.4 vdc today to see what heat it produces.
 

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Discussion Starter #20
I'm comfortable enough from the testing of the front ELSD Solenoid to mount my switches. Not the best place to easily see them, but I was going for inconspicuous and accessible only to the driver.
 

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