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# Stinger 4 Instruction Manual - page 53 / 59

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Base PWM Frequency The base frequency is used to calculate the operating frequency of all PWM outputs.

Aux PWM Frequency This setting should be set to 255 wherever possible. It determines the pulse frequency of each PWM output according to the following formula.

Output frequency = 255 / Aux PWM Frequency * Base PWM Frequency. ie: By setting the Base PWM Frequency to 20 Hz and the Aux PWM Frequency to 200 will result in an output frequency of 25.5 Hz. ( 255 / 200 * 20 = 25.5 )

NOTE: Reducing the Aux PWM Frequency number will increase the frequency for the output but there is a trade off. The duty cycle adjustment resolution of the output will be reduced. ie: If this frequency number is reduced to 100 for example, the output frequency would increase, but the adjustment resolution will be reduced from 255 to 100 increments.

Adjusting the Duty Cycle PWM outputs are used to control devices that can vary their state like idle control valves, these devices can be fully closed, fully open or anywhere in between. This is achieved by varying the ratio of on-time and off-time of the output signal. This is referred to as duty cycle. Longer on-time will increase the supply of current therefore opening the valve further.

You can vary the duty cycle of a PWM output according to engine RPM, manifold pressure or throttle position by entering the amount of duty in the duty table. The maximum allowed number in this table is determined by the value of the Aux PWM Frequency. ie: if the Aux PWM Frequency is set to 120 then entering 120 in the duty table will result in maximum duty thereby supplying maximum current. A value of 60 will result in 50 percent duty and therefore 50 percent current.

Reverse Acting The Reverse Acting function will reverse the duty cycle of the output.

This function is needed when a valve works backwards, eg. Bosch BMW idle valve. With these types of valves, increasing the duty cycle will actually slow down the engine and reducing the duty cycle will increase the idle speed.

Stinger 4 instruction manual version 2.0

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