jimstim rpm pots

Building and using the Stimulator to test your Megasquirt

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jimstim rpm pots

Postby atthetrack17 » Sat Mar 05, 2016 11:18 am

Hi, my rpm pots(when testing with jumper wires) on the jimstim used to show correctly on the leds when turning the pots clockwise, by blinking faster. Today when I turn the pots its all or nothing. leds are off to the left and turn on when the pots are all the way clockwise. I have removed the cpu and tested the volts and also checked the pots. All checks came out normal. Do I need a new CPU? thanks, Brad
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Re: jimstim rpm pots

Postby racingmini_mtl » Sat Mar 05, 2016 11:56 am

Are you sure you have all the needed jumpers and that you have selected a valid wheel mode? Also, check the voltage at the pots when you turn them; that should go from 0V to 3.3V.

Jean
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Re: jimstim rpm pots

Postby atthetrack17 » Sat Mar 05, 2016 1:03 pm

Thanks Jean. Yes, all jumpers are off and wheel mode switches are all off.
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Re: jimstim rpm pots

Postby racingmini_mtl » Sat Mar 05, 2016 1:21 pm

All jumpers off will not work. You need to check again because you need some jumpers and you need to make sure you're using the right ones for your specific setup.

Jean
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Re: jimstim rpm pots

Postby atthetrack17 » Sun Mar 06, 2016 8:00 am

Here is what I have been following. This is from the instructions for the jimstim. Thanks, Brad

Testing the tach signal

If the Jimstim voltage regulator and/or CPU are getting hot when power is applied, refer to the next section (Troubleshooting tach signal, CPU and 3.3V)..

Testing of the tach signal can be done using the LEDs. This test will also verify that the Jimstim CPU is working correctly. To do this you need to do this:.
Power off the JimStim and disconnect it from the MegaSquirt
Remove the pull up jumpers
Remove the primary tach jumper
Set the wheel mode to distributor mode (all DIP switches off)
Connect a wire jumper from the primary tach header (where the jumper usually goes) to an IAC led. Use the primary tach header pin closest to the pots (away from the PRIMARY TACH text) and the last pin of the 10-pin header (pin closest to the pots)
Connect a wire jumper from the other side of the IAC led to 12V. Use the next to last pin on the 10-pin header (just besides the pin connected in the previous step) and one of the pins on the 3-pin header besides the voltage regulator.
Turn the RPM pots all the way counterclockwise.

Once the connections above are done, power up the JimStim (with the MegaSquirt still not connected) and start slowly turning the RPM FINE potentiometer clockwise. You should see the led start flashing and it will flash faster as you turn the pot more.
Warning: With the JimStim not connected to the MegaSquirt, the bottom of the board will rest on a surface with all the exposed leads and solder pads. Make absolutely sure that the surface is non-conducting and that there is nothing that could make a short also on the surface. A short may cause permanent damage to the CPU and possibly other components..
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