Not posting everyday. Sorry...

I've been working on a personal project that I've always wanted. A low cost battery operated night light. A smart night light.

I've completed the first proto and developed the code to make the first proto functional. The major objectives are:
1) Low power consumption.
2) Regulated LED with multi-brightness levels
3) Low battery detection
4) ambient light detection
5) microprocessor based
6) Multi-cell operation

The UI that I created was a simple 5 menu wrap around system. It powers up in high (10mA) and toggles to Medium (2mA), Low (0.5mA), Special Function 1, Special Function 2.

Using a standard photo sensor I was able to set the sensitivity to a very low light level. Where I have it in the bedroom and with the one window shade mostly closed the daytime ambient is pretty weak. Most of my other attempts have not been successful at detecting the daytime light. This one performs very nicely.

The Night Light has a unique multi-cell configuration. For 123s it can support 3 cells and operate off two or three automatically. For AA cells it can operate off three or four cells automatically.

The boards footprint is the size of the four AA batteries and the battery holders mount to the backside making it a solid unit with the batteries being the bottom base of the unit. The board can be loaded with three 123 single battery holders or four AA battery holders.

There is a little button on the board that allows the user to change levels or in the future change settings and parameters.

During the daytime the unit goes to sleep drawing less than 1mA in the off state. More likely it will be around 200uA or less. If I can re-arrange a few things I can get the sleep state to around 2uA or less.

I just made the PCB for revision 2 which incorporates the changes I found on rev1 and changes the primary LED to a Luxeon emitter since these are now abundant and should make the light brighter for the same LED drive current.

Right now the menu selection is only available when it's not asleep. This is problematic and I'm thinking of how to address this without the code getting all mangled.

This weekend my work on this stops and I go back to jobs that pay the bills. My goal is to make 2-20 of these for personal use and to give to family and friends. The boards is a reasonably large size and won't be dirt cheap.

Assuming I brought this to market the finished product will not be too expensive. I know that for family and friends they will all be AA versions as none of them have 123 batteries.



This is a tentative UI proposal for the night light. Under normal circumstances you will only have access to low, med, high. To get into the Special functions requires some additional effort.

Entering and leaving the special functions in the above proposal is to hold the button down for greater than two seconds.

One of the cool things in the special function will be the capability to set the sensitivity of the photo sensor for different ambient light conditions or just turn it off.