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Rev-limiter operation
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Post Rev-limiter operation 
Ok, let me get this straight;

normally the trigger is low (off) and the SMBT... does not conduct, making the gate -ve via the ground link.
then when trigger'd the SMBT conducts and the makes the gate +ve which stops the flow through the MOSFET.

is that correct?

i am trying to modify this arrangement so that the MOSFET is off when the trigger is off, then when there is a +5v signal the mosfet is turned on. but am encountering problems (probably in my choice of Mosfet (STD30PF03L) and transistor (FMMT491TA)

any help would be great,

Cheers,
David

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David,

The MJLJ rev-limiter output is as follows:

Below rev limit: high impedance (open circuit)
At or above rev limit: connected to ground

The SMBT2907A is there to invert the output so the P-Channel mosfet is on when the rev limit output is de-activated.

To have the mosfet on when the rev-limit output is enabled would involve eliminating the SMTB2907A and having the rev limit output drive the mosfet gate directly. Of course, you would need a pull-up resistor on the gate when the rev limit output is inactive.


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Brent Picasso
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