Problem burning up D8

[fairmont50]

All,
I have been very successful in turning D8 into a resistor with values ranging from 180 - 450 ohms. This causes the converter to lock up very shortly after the shift to second and remain locked until the shift back to first (very harsh shifts to say the least). I believe that it is probably being caused by an inductive kick from the tcc circuit (4l80e pwm tcc). I have added a 270 ohm resistor in series with d8 that will hopefully protect it but still allow it to protect the transistor. Does this sound reasonable?

Also, everything that I have read shows the gm tcc being pulsed with a frequency of 30 or 32 hz but tuner studio will only allow a maximum of a 10.888 ms pulse period. Is this something that I can change in the .INI file without causing any problems in the code?

Thanks,

Chris

[Bernard Fife]

Chris,

D8 is part of the TCC output, and you are obviously using PWM with the TCC. Because you are doing PWM, you must add a recirculation diode to the TCC circuit. This is a 1N4001 or similar that has the non-banded end on the TCC output, and the banded end on the 12V supply to the TCC solenoid. It should be physically located as close to the solenoid as is convenient. This diode isn't on the board, because it's functions better close to the diode, and prevents bringing flyback noise into the GPIO board.

Changing the INI won't change the range of actual frequencies available in the code. (It will cause an under-run ion the submitted value from TS, which will then give you very, very high frequencies instead). So use a multiple of 31 Hz.

BTW, the frequency you drive any solenoid at is a function of the driving circuit, as well as the solenoid itself. Since our circuit is very unlikely to be exactly like what the OEM uses, the optimal frequency likely isn't the same either. At this point, we don't have a good method for the average user to determine the best frequency, but we are working on developing a method that anyone can use.

Lance.