You can use HC-SR04+ or HC-SR04P for 3.3v operation, and the only wiring change is the VCC pin connects to 3.3v

My own modding of the PIR sensors are generally not for WiFi (such as ESP modules). Turning lighting on in response to motion doesn’t require WiFi (nor even a µC), which would consume a lot of current compared to the PIR. You could have a µC with the PIR output driving to an input pin on the µC, configured to wake on pin change. Wake, log the event or do whatever else and go back to sleep. PIR modules running my 1-3W LED driver with fairly frequent foot traffic (but not like downtown in-city) will run for 6-8 months if not longer in my environment, but then the LFP cells I have are 50Ah each.

Thanks, I had not pondered battery. How long does it run on battery? Does your code turn off wifi until it detects motion?

I do love my hot air stand, but that is still small stuff for me.

Thanks,
Grey

If you have 5V to start with, yes, you can power the PIR Vin without needing to mod the PIR. The current consumption of the PIR is very low, so the losses aren’t that significant.

The point of modifying the PIR module to bypass the onboard voltage regulator (either by feeding it from another point on the PCB beyond the regulator, or bypassing the diode and regulator) is for people using say, a single Lithium Ion cell, to power their project (for which their µC is likely 3v3), and when passed through a diode and an LDO, suddenly, that’s insufficient to run the PIR module.

I have and use a lot of LiFePO4, which when FULLY CHARGED are 3.6V (and don’t stay there for long – 3v35 or so is where the bulk of their charge is) – there’s NO room for a diode drop with that, much less the demands of an LDO after the diode.

Note that those using say a Lithium chemistry don’t want to have to have a boost circuit, or say a 2S battery configuration just to run the PIR, when in fact, the PIR wants 3v3 itself.

SMD isn’t for everyone, and no judgement here, but as SMD goes, the miniMELF (diode package used here) and the SOT89 (LDO) are both very manageable parts, but then rework isn’t everyone’s cup of tea – removing an SMD device is a bit more of a task than installing one on a bare board.

Can I not just use the 5v pin on a wemos D1 mini?

Michael, the PIR modules I have (a commodity part on AliExpress, often sub-US$1 each), do not have the pads where this article shows the red wire connected. What I do (since I can manage to connect power with correct polarity), is remove the polarity protection diode just to the left of the Vcc header pin, as well as the vreg, and bridge the pins where the diode had been and the centre pin of the vreg to the one on it’s right (towards the middle of the PCB). This loses the 0.6V drop of the diode as well as the overhead for the LDO. Once so modded, I provide 3v3 on the Vcc pin (whose regulation comes from elsewhere), using the standard header pins. In my typical use, I have an LED driver board that piggybacks on the back of the PIR, so routing a wire somewhere else isn’t the level of tidy I’m looking for. If you run 3v3 to the location shown in the article, you would NOT run anything to the Vcc pin.

Note that the elcap in the lower left (if the Vcc/Out/Gnd is at bottom centre) is a buffer cap, not that the board itself should use much juice. If you’re not bridging the Vcc path or not supplying power at the Vcc pin, there’s a very good chance that cap will not be charged (it is on the INPUT side of the vreg, so shouldn’t be charged if the board is being supplied by 3v3 on the output side of the vreg, but I might be wrong – I haven’t worked up a complete board schematic).

Removal of the parts is trivial with hot air – the LDO is a bit more of a bother with a stick iron.

Once doing this modification, you supply the module with 3v3 on VCC correct?

If that’s the case, you could jump that H pad to VCC right?

Sara;
As usual, thanks you for your excellent help. The Adafruit article is exactly what I needed.
Ray

Hi Ray.
I think this article might help: learn.adafruit.com/pir-passive-infrared-proximity-motion-sensor/testing-a-pir
Regards,
Sara