Previously, PadreSJ mentioned considering an addon for his battery-powered deodorizer fan that wo...

[G+_Stede Bonnett]

Previously, PadreSJ mentioned considering an addon for his battery-powered deodorizer fan that would cutoff in a low-voltage situation to prevent damage to the LiPoly battery packs. That sounded like a good idea to me for battery operation, but as I will generally be using an AC adapter I decided since the fans are audible at full speed it would be nice to quiet them when the area is occupied.

 

So, this controller has two optional features:

First, it has a battery voltage monitor which will kill power if it drops below a threshold (and stay off until reset) to protect the cells.

Second, a PIR motion sensor that triggers the software to change the fan speed (for a defined time period).

It's also possible to adjust a couple variables so it only runs when motion is detected, and of course you can control the time is stays in that state.

 

The specs are for 5V micros, but it's really easy to adapt to 3.3V - I might do an IoT version with BT or WiFi that is 3.3V (and that's when you know that this whole project has gotten out-of-hand :-) )

 

All the interconnects can be made with a mix of header jumper wires which you can buy/make and assemble without soldering.

 

No case made yet as I'm waiting for some more Pro Mini's to come in. I'm probably going to attach it to one of the screws that holds the top of the filter.

 

See the link for parts and assembly notes:

https://github.com/iocon/Deodorizer-fan-controller

[G+_Eddie Foy]

Looking at the schema, the resistor voltage divider is the low voltage drop out?   Does the arduino go into a stop state once the battery level trips it?  Batteries tend to gain back some voltage when load is released.  So this can cause it to turn on and off.  Once the battery hits the low level , the system to should 'latch off'

[G+_Stede Bonnett]

Eddie Foy yes, it waits for 32 samples below the threshold (total since last start) and then goes into deep power off (and shuts off the PIR) "forever". After that there is just leakage from the micro's voltage regulator, the power LED if present, and ~40uA from the divider.

[G+_Stede Bonnett]

I just cleaned up the software and tested some more configurations and low-power features.

The schematic is updated on Github (and I removed the one here to prevent confusion).

The lowest power options require some parts that would be hard to assemble point-to-point so I'm going to layout an arduino-shield-style board for the Pro Mini or Nano that can be configured with all of the options.