Rev-limiter operation

Discussion on the Hard Rev Limiter module, currently under beta testing. <a href="http://www.autosportlabs.net/Hard_rev_limiter_1.1.0">Project Information</a>

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hcp474
Posts: 9
Joined: Sun May 25, 2008 1:42 pm

Rev-limiter operation

Post by hcp474 »

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

brentp
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Posts: 6160
Joined: Wed Jan 24, 2007 6:36 am

Post by brentp »

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.
Brent Picasso
CEO and Founder, Autosport Labs
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