create lamp for my child's room based joule thief

hi, sorry for my bad english, i’am french but i think is possible for you help me

I am looking to create a lamp for my child’s room, I am not looking for a lot of light but a lot of autonomy.

I have looked at a lot of circuit type joule thief, but I can’t find the ideal component to have light on the duration (more than 300 hours with a battery type D LR20 1.5v)

I have several links on my pc but I can’t find the best components.

Could you help me?
I am looking to create a lamp for my child’s room, I am not looking for a lot of light but a lot of autonomy.

my actualy desktop _

is difficulte for me because i’m not expert on electronic project and few time free because my son have 10 month and difficulte follow topic for chose the best.


I saw this led, I don’t know if it can make a light for the room at night, but it doesn’t consume much energy it seems.

from your experience as a light expert, what do you think?

I saw the module of Gchart\_x_tr_sl=en&\_x_tr_tl=fr&\_x_tr_hl=fr&\_x_tr_pto=wapp#comment-1657535

do you think this module can be adapted?

thank you for help

i would not do it

many of the parts have to be hand made and you can just get a light with firefly mode and also use it for something else too

they can be .1 lumens, 500 hours on a rechargeable 18650

also the actual joule thief lamps blink, which is not really a good night light

firefly lights

thank you for your answer,

I understand about taking ready to use, but I would really like to try it.

my final goal will be to create a 3d box for the system, and i got the diffuser from a bulb.

but nothing prevents me to recover an existing pcb and to adapt it :wink:
I have trouble with lumens / lux / cd etc…

0.5 lumens is enough to make a night light ? for room ~ 12m²

what do you think of the led I put on the 1st post?

I don’t want 18650 battery or others,

I want a normal lr20 (that we throw away when it’s finished, so it’s 1.5v and not 3)

very thank you

½ lm is VERY dim. Think of an on/off indicator light on a pushbutton. That dim.

If diffused, you’d be able to see the light, but it would be largely unable to light up a room as a nightlight.

If you have a flashlight which is reviewed here by someone who spells out, say, that low is 10lm, medium is 150lm, etc., you could then guesstimate what that 10lm would be like, and whether that’s enough, too bright, or too dim.

If you’re going to be using D cells, great, as they tend to leak much less than hateful little AAs and AAAs, but it’s still possible.

That driver from gchart looks like a good starting point. You could solder wires from that to the LED (s) and battery-holder.

Are you wanting to use a specific LED emitter,

or are you just interested to get something that works and interested in learning and playing with some electronics?

i don’t know your knowledge, skill and ability level with respect to electronics and LEDs, so excuse me if this might be too basic:
To get started and learn some electronics i would recommend to get a 3 to 5mm LED and some components to build up a basic JT circuit, then you can test, experiment and measure how changes affect the brightness and runtime.

An alkaleak D cell has nominally 20,000 mAhr capacity. A red 3mm LED will light up with a current of 20 mA, so it would theoretically run for 1,000 hours. But the voltage of the D cell will drop as it is consumed until it is too low to provide the forward voltage required for the LED; the JT provides a way to boost the voltage to allow the LED to burn even with a low voltage cell.

Hello, thank you for your answer,

I am not a pro in electronics, I understand some basic things because I am a maintenance technician, but I really work with more powerful voltage (380v).

I have a small multimeter, but that’s all, I think that on the forum, there are people who have done a lot of testing on the joule thief, that’s why I would like to take the best possible assembly for my case, maybe a chip type ZXLD381FHTA or other, will be more efficient, I do not know, because it seems to me that the cut is done at 0.9v.

I would really like to find a solution for a led or 2 leds for the night (just to have the light in the room very low, for the fear of monsters)


I can also take several leds to find the best one,

I don’t mind taking several types of material (5 or 6 leds + 3 or 4 chips + various resistors and other components)

but the goal for me is to find what to take to start making test setups.

if you have a list of known and efficient material ( all on the same site ), i want to.

so I just have to order and try it, and I’ll give you a feedback on it so we can look at the possibility of improvement.

The man himself who coined the term: Make a Joule thief.

I have a few projects using QX5252F (Djozz clock mod). It’s is similar to YX8018, which are typically used is outdoor solar lamps. I have couple running alkaline battery at sub lumen for a few months, and another running fairy lights at ultra low for almost a year.

I use rngwn 5mm these look better and have lower vf than cheap ‘cold white’ ones.

Yeh, there are a handful of those type chips out there. Got a small stockpile from AX ages ago, just for s&g.

For quick’n’dirty, anyone can scavenge the board from a solar-light, but the kind that takes NiMH and not LFP cells.

hi all,

what is rngwn ? manufacturer or technologie ? i like the warm white, and very dislick cold

I don’t really want to recuperate a solar lamp, I would rather make it myself (happier to do so) and I think that you on the forum know really well the leds to help me =)

I think that the solar lamp uses an old technology and that there are better now.

ps I love the led clock, I love the light, maybe I’ll do the same one later (when I’ll have finished my child’s lamp in 3 years ahah)

hi have filter led on the site, but i don’t think what is the best, do you have idea ?

not smd

and site 2


or other if you know better

i have contacted mail and for help to found better
i have difficulte for found on the forum, and i’am ready for buy 10 ou 15 different leds for choses after


DatiLED makes battery drainers that seem like they may be close to what you are looking for?

They work with any 1.5 Volt cell (some will also work with 3V cells).

What holds the LED board to the Positive terminal—is there a socket or clip to secure it?

It seems that these were sold as a one-time build on the candle power forum, are they still available somewhere?

Any pictures or schematic of the circuit board?

They attach to the cells with magnets.

DatiLED puts them up for sale in batches, but they sell out quick. You might want to contact him for more information.

from Diodes .com aka Zetec

Hello to all,

I answer a little late, but I continued the research.

The magnet system presented by xxo does not suit me.

I think I’m going a lot wrong in the research, probably because I’m not experienced.

for example, this morning i looked at the iron ring to put the wire around, but even on that, they say there are several differences.

Some people also talk about germanium transistors, which would be better.

Basically, there are a lot of choices, but it’s hard to choose