Biker Bear
Enlightened
Before my question, a bit of background:
Every Labor Day weekend, I go on a camping trip in the Sierras hosted by a local club. The campsite is a primitive one, fairly heavily wooded and a few years ago the "LED throwie" concept gave me the idea to create trail marker lights - so if someone had their flashlight fail, they'd still have something to go by. The design I eventually settled on was a white 5mm LED, a CR2032 coin cell, two "bingo chips" as insulators and the whole thing held together with a small binder clip.
These are put in small plastic bags and pushpinned to the trees, which makes retrieving them ("pack it in - pack it out") reasonably quick and easy. They run much longer than the necessary "design life" of 96 hours, though of course the brightness gradually drops off over time. The LEDs are aimed at the base of the tree, in part to help illuminate the ground, but also to avoid ruining people's dark adaptation. That last - not wanting them excessively bright - works well with wanting a design that can last 4 days without needing battery changes, etc.
What I'm wondering is if there's a reasonably feasible low-current regulation circuit that would work for something like this. I envision a small circuit board with a vertical coin-cell holder on it, a white LED (possibly a SMD) on the other side and the regulator circuit components wherever they need to go. The idea would be to have this drain the cell to failure in 100 hours, and provide (reasonably) even lighting through that period. My understanding is that a CR2032 has ~220mAh, so the average current draw would be about 2mA. Even allowing for some "waste" in the circuit, providing 1.5mA to the LED for 100 hours seems feasible.
I realize the price of having something like this made in a relatively small batch could be unacceptable, but right now I'm just wondering if it's technically possible.
Every Labor Day weekend, I go on a camping trip in the Sierras hosted by a local club. The campsite is a primitive one, fairly heavily wooded and a few years ago the "LED throwie" concept gave me the idea to create trail marker lights - so if someone had their flashlight fail, they'd still have something to go by. The design I eventually settled on was a white 5mm LED, a CR2032 coin cell, two "bingo chips" as insulators and the whole thing held together with a small binder clip.
These are put in small plastic bags and pushpinned to the trees, which makes retrieving them ("pack it in - pack it out") reasonably quick and easy. They run much longer than the necessary "design life" of 96 hours, though of course the brightness gradually drops off over time. The LEDs are aimed at the base of the tree, in part to help illuminate the ground, but also to avoid ruining people's dark adaptation. That last - not wanting them excessively bright - works well with wanting a design that can last 4 days without needing battery changes, etc.
What I'm wondering is if there's a reasonably feasible low-current regulation circuit that would work for something like this. I envision a small circuit board with a vertical coin-cell holder on it, a white LED (possibly a SMD) on the other side and the regulator circuit components wherever they need to go. The idea would be to have this drain the cell to failure in 100 hours, and provide (reasonably) even lighting through that period. My understanding is that a CR2032 has ~220mAh, so the average current draw would be about 2mA. Even allowing for some "waste" in the circuit, providing 1.5mA to the LED for 100 hours seems feasible.
I realize the price of having something like this made in a relatively small batch could be unacceptable, but right now I'm just wondering if it's technically possible.