- Tue Aug 25, 2015 4:44 pm
Hi, working away at the moment so I can't do any testing. I will do & update the first post as soon as I can.
DaniloFix wrote:Thanks for the suggestion - you think using a MOSFET as a switch will add a "delay", keeping the CH_PD high long enough? I plan driving the setup from 3.3v regulated battery source, so both gate and source will be 3.3v - you know any MOSFET's that will be useful ?
Hi, it depends on the MOSFET & the circuit (it could even be a problem turning it off, but easier to fix), but we only need 500ms (to be on the safe side). Only testing will tell & you may still need a capacitor on the gate.
As for the MOSFETs, using the second circuit where a switch replaces the PIR, I see two simple options:
1. Use an N channel MOSFET in place of the switch. You wil need a cell of some sort to drive the gate, a CR2032 should be fine & last for ages. Connect
gate -> cell +ve
cell -ve -> sensor
sensor -> source
2. The option I favour. Use an P channel MOSFET in place of the switch. Connect the sensor between gate & ground.
With both the above options I would start buy using a 10K resistor in series with the gate to limit possable currents & slowly reducing the value if it doesn't work.