This is a very simple night light that I made while trying to find new things to do with some solar garden post lights that came with a single solar cell feeding several posts. I really just bought the set for the post lights since they were quite neat.
I used the original circuit board that holds a single LED and resistor, but added a two cell AA battery holder. The original LED was swapped for a warm white strawhat LED (wide angle domed lens) which effectively operates at around 1mA on a pair of NiMh rechargeable cells.
Due to the low current it runs 24/7 for literally months on a single charge, and even when the battery is starting to run low it still emits light but at a slowly reducing level. A quick one minute boost in a battery charger is enough to last a whole night, but a full charge sets it up for a few more months of light.
I used the original circuit board that holds a single LED and resistor, but added a two cell AA battery holder. The original LED was swapped for a warm white strawhat LED (wide angle domed lens) which effectively operates at around 1mA on a pair of NiMh rechargeable cells.
Due to the low current it runs 24/7 for literally months on a single charge, and even when the battery is starting to run low it still emits light but at a slowly reducing level. A quick one minute boost in a battery charger is enough to last a whole night, but a full charge sets it up for a few more months of light.
Would alkaline batteries last nearly as long or does it have to do with the batteries’ internal resistance?
That's an amazing video! Another cheap yet extremely useful update would be a photoresistor, it could save at least another month of battery life
Some ukrainian guy done experiment with these kida lamps.
He took batteries from like 7 different brands, solder them in pairs with leds and add different resistors in 4 of them.
Lamp made of Duracell batteries without any resistor was still glowing even after 400 days and that's amazing.
fantastic explanation and example- thank you
I've been trying to find something out of the box I can buy like this… since I'm not so savvy at electronics. I just want a very low light glow in my planter to illuminate under the leaves of my ivy… But don't want to be constantly changing batteries or running a wire to the hanging pot. I might try building this if I can get everything off Amazon.
I dont think 2mA is enough to light that led. More like 20 mA.
STAINLESS STEEL CHOOB
We all need a bit of comfort, 😁👍
I made a small night-light of 1 white LED automatically turning on when dark (no off switch), running on a single AAA battery, since the 18th of September 2018(!). Its still giving out light and today its the 17th of June 2020. Its self regulating in the way that if you put it down on a table the light will adjust itself down from its own light feedback, but when you hold it up it will shine up and there is more than sufficient light to see the whole room. I think its pretty amazing 🙂
Thank you for you videos.
I don´t understand electronics. Could you specify what and how exactly to look for parts in ebay. Resistor, battery circuit, led. Thanks.
Where did you get it? eBay? Why not add a photo-resistor (and some circuitry) to make it not be lit during daytime? New video project?
At that low of a current, I'd bet the natural self-discharge rate of the batteries would be a quite significant factor in the overall run-time of the LED, especially if you're not using low-self-discharge NiMh cells.
I say this because I've read several sources that state a "normal" NiMh cell will self-discharge to "dead" within about a month or two, and this circuit has a calculated run-time of a little over 3 months.
The lamp looks large enough to hold a couple of D-size cells (IEC name LR20).
Using those I bet you could get a year or more out of this same circuit, as that size of cell is rated by Energizer to be 20,000 mah at 25ma, but lower current should make it last even longer than that capacity would indicate (due to Peukert's Law).
Those look like the same cells I got from Lidl. Seems like Lidl sells two different types and those are the bad ones 🙁
They are supposed to be 2500mAh but when IO analyze those I get 1700mAh max (most barely reach 1400).
After putting them on a weight-scale it was pretty clear that those cannot be 2500mAh.
This video inspired be to make a night light for the bathroom. That way I don't need to turn the lights on in there and adapt the eyes to the bright light and then readapt to the dark hallway. Enough light to see what's one is doing in there.
I used a 2xAA "end to end" holder with two 2000mAh cells. I used a "blob" pcb from a LED tealight instead of a resistor.(Ran just fine on 3v button cell so I assumed ~2.4v from AA's would be safe.) The original yellow 3mm LED was swapped for two 5mm warm white in parallel. Everything fits inside a spice jar together with two silica gel packs. Mosty to stabilise everything inside, but they should also keep it dry.
Running two leds in parallel should make the light more efficient and I think the flickering helps too. I measured the current and it vary between 1.5 and 2.3 mA, with an average at something like 2mA with fully charged cell. Should give around 1000 hours or 41.66 days of use.
It's pretty impressive how little power recent LEDs needs to run, which probably explains why some garden solar lights come with such tiny batteries now. One set I bought uses a battery in each lamp about 1/3rd the size of an AAA. Quite annoying as these batteries are difficult to get hold once they fail to hold a charge.
I have a few basic (non blinking) 15 LED fairly lights set that run on 2 AAs that I hang from wall-mounted speakers in December. I ran them continuously using 2000mAh Ni-MH AAs and they ran for at least 48 hours before the green and blue LEDs starting fading out. After another 24 hours, the red and yellow LEDs were quite dim. Based on the time it ran all the LEDs, this would give a runtime of 30 days for a single LED, pretty impressive for these two year old sets.