Completed Project Automatic Pantry Light

Thread Starter


Joined Mar 24, 2008
So one of my favorite stores harbor freight shows these little work flashlights. They are incredibly bright and use 3 AAA batteries to power them up, they are a bit under designed as far as reliability, but they pull over an amp from these little batteries. So they are real battery hogs. I have tried rechargeable lithium which can provide the current and maintain the voltage but they burn out the light strip.I use a 1Ω resistor to drop the voltage down .

Work light.png

I regularly buy them to harvest the light strips and even the batteries( hey they are selling these things for 99¢ at the moment.a friend of mine is using one as a pantry light. She would like to add a option similar to a refrigerator light where it turns on when the door is open. It so happens I have window sensors for an alarm system. The switch is closed when the magnet is next to the sensor . So somehow I had to reverse the action to closing a switch when the door was open so I came up with this circuit . My soldering job is ugly enough I didn't worry about pictures of the interior in this case.

Light interface.png

I auditioned an IRF520 which is a conventional MOSFET, obviously since it would not work at such a low voltage, interestingly it did switch but did not turn fully on. So I used a logic level MOSFET (16N05L) which worked very well.

I soldered the 10MΩ to the gate of the MOSFET and attached the sensor wire from there. Since I only have one working hand I used this tool to assist:

Tool.jpg Tool2.jpg

I stuffed the transistor in an empty space in the flashlight, the sonalert was an an afterthought to be sure the light went out when the door was closed.

Thread Starter


Joined Mar 24, 2008
Light Breakdown:
Here is the schematic of this light.

Original Schematic.png

And this is the interior:
230310_213210.jpg 230310_213654.jpg

Ive disassembled a few over the years, that is a jig I built to help me quite a few years ago. Like I said the device is lacking basic reliability practices.
Among the parts I have harvested:
3 High intensity LEDs
1 Light bar (it really is neat IMO)
Battery contacts
3 AAA alkaline batteries.
Someone might have an application for the push on/off/on switch but I haven't.
The design depends on the battery pack dropping under 4VDC when on to not burn out the light bar ( measured 3.8V on this project).
Last edited: