Trigger Circuit

[heida11]

I have a PIC driven digital RF link working at reduced power.
(Currently limited to max PIC voltage.)

I would like to find a way to provide 9 volts to the transmitter's
trigger input while providing the 5 volts or so required by the PIC.

Currently the trigger is wired directly to the PICs output pin.

The attachment is as far as my knowledge takes me.

Would appreciate any ideas.

 

[Nigel Goodwin]

I have a PIC driven digital RF link working at reduced power.
(Currently limited to max PIC voltage.)

I would like to find a way to provide 9 volts to the transmitter's
trigger input while providing the 5 volts or so required by the PIC.

Currently the trigger is wired directly to the PICs output pin.

The attachment is as far as my knowledge takes me.

Would appreciate any ideas.

You simply need an open-collector driver, with the collector having a pull-up resistor to the 9V supply - please note though, this inverts the logic - but is easily cured in the software.

Many PIC's have a single open-collector output pin (usually RA4), but I don't think the 12F675 does?.

Are you sure the transmitter requires a 9V input signal?, it might work quite happily with a 5V signal - you could try it and see.

 

[heida11]

Thanks Nigel.

I used an NPN transistor with a 1K pullup to draw sufficient current.

The output is more than double compared to 5V.

Thanks again.

 

[hyedenny]

Hi,
The 12f675 does not have an open DRAIN output. Make your own to control the 9v trigger.