Simple MOSFET load switch design

Thread Starter

FranciscoB

Joined Feb 8, 2014
38
I would like your help designing a circuit that would use a PIR sensor to turn ON an ESP32 CAM.

The PIR outputs 3.3V when it detects motion and remains HIGH for up to 5min ( 1sec min, user defined). This signal would pull the P-Channel Mosfet LOW, powering the ESP32 CAM, which would send me a notification to Telegram with the option to take a photo. I would then either turn the camera off by pulling the N-Mosfet gate LOW again (assuming no motion detected by the PIR), or I could just set the output of the PIR to remain high for only couple of minutes to give the camera time to send a notification and expect for my instruction to take a photo or not.

I read this document: https://www.onsemi.com/pub/Collateral/AND9093-D.PDF

Not sure if I got it right and which resistor values to use. The camera momentarily pulls up to 300mA when doing WIFI operations.

Please take a look at the circuit diagram in attachment.photo_2021-04-21_20-34-50.jpg
 

AnalogKid

Joined Aug 1, 2013
9,351
1. Add reference designators to *all* components.

2. Delete R2. It decreases the gate voltage (Vgs) of the FET. Which FET? That's why you need reference designators on everything.

3. Is the diode (which diode?) driven by the camera? If so, is it supposed to pull the FET (which FET?) gate low? If so, it is backwards.

Please post links to both MOSFET datasheets.

Since you are mixing 0's and O's in the same part number, put a slash through the 0's. My search for an A03401 came up empty.

Correct and re-post.

ak
 

wayneh

Joined Sep 9, 2010
17,153
The only problem I see offhand is that the A03401 will have a resistance of >50Ω with the gate-source delta of only 3V or so. I think that'll be a problem at full load and drop the voltage too far.
 

du00000001

Joined Nov 10, 2020
77
Oh yeah - datasheets from our lately found Chinese friends tend to have at least as many errors as their silicon :confused:
The "Ω" at the diagram axes have to be "mΩ" - consistent with the values given in the tables.
 
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