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Sub-page for questions for MembersPage/SteenAndersen === Questions === ==== How do i change the IAC PWM Frequency ? ==== I have been testing my Idle Valve with the PWM output from GenBoard. The valve is a BOSCH 2 terminal spring loaded type 0 280 140 531 from a 91' car, 8.7ohm DC resistance thats a 1.4A LoadI use '''iac_sol_channel=60 ''' for IAC output.I experimented with mdi00..mdiff command to se the valve open and close, and it seems to work, but i hear the PWM frequency as a high pitch (i read 2 KHz somewhere). But the inductance/hysteresis/losses in the Valve is so high that it gets VERY HOT ! I get so hot that i'm afraid it will fry if used in the car in a hot engine bay. The PWM Frequency is way to high for this old Motronic Idle Valve, it should maybe oprate at 100Hz not 2KHz. I have been lookin in softpwm.c and iac.c but i do not understand what's going on in the code (I'm not used to C programming). OK i see that the PWM duty cycle is set in iac.c with this. <code> softpwm_set(&idle_pwm_soft, pos); </code> but i dont see any frequency settings in the init_iac procedure theres just one statement. <code> softpwm_init(&idle_pwm_soft, 0); </code> * So ''' how do i Change the PWM Frequency ? ''' AFAIK there is no way to change the PWM frequency in config but it should be an easy hack. But instead of doing that it may be good to look at the the mechanics. The valves i have on my Audis consume between 2 and 4A depending on model and the plungers are very heavy to act as a proportional valve instead of a PWM valve. I think this is how most idle solenoids work. When thinking about the power over the valve you find 1.4AX14V=19,6W over yours and I find 4X14=56W over my nastiest idle valve. This is a lot of power and if used in the lab without airflow it will get hot, I suspect that it's cooled by the air flow through the valve when used in the car. I can't see how the high frequency would make the valve run hotter then PWMing the current at a lower frequency. The FET and the flyback diodes may on the other hand get hotter at this frequency then at 100Hz. An easy test would be to check if the solenoid runs hotter at 80% then it does at 100%. I suspect that it doesn't. ---- My subpage for questions that i need an answer to. Questions witch i have solved or feel is answered is moved to MembersPage/SteenAndersen/History page ----
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