The circuitry in this light is very simple.
It does a decent job of dimming without flicker, but can drive the LEDs very hard at its brightest setting with good batteries.
The dimming function is achieved by varying the base current of a standard NPN transistor resistively. The potentiometer passes very little current.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
It does a decent job of dimming without flicker, but can drive the LEDs very hard at its brightest setting with good batteries.
The dimming function is achieved by varying the base current of a standard NPN transistor resistively. The potentiometer passes very little current.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
http://www.bigclive.com/coffee.htm
This also keeps the channel independent of YouTube's advertising algorithms allowing it to be a bit more dangerous and naughty.
My batteries went flat in a few days … the switch was not working correctly … it seems the tiny conical spring applies too much force on the " clip on " switch plunger ( grey in your example ) forcing it up the control tab ( so it never switches off ! ) .. if you remove the conical spring the flat switch blade works just fine without it ! .. however , a tiny slide switch fitted to the side of the case ( precision drilling / Dremel™cutting ! ) wired into ( any ) battery lead will ensure a 100% reliable switch off , but requires several minutes of modification ( ? )
Zinc Chloride cells have a higher internal resistance and ( should .. ? ) limit the maximum current, helping to save the LEDs at full brightness .. however the " Kodak " types ( see comment a long way below ) might not last that long … ( other makes are available ! ) … FYI , alkaline types LEAK HORRIBLY, ( as you guys probably know ! ! ) …. but a very nice lamp from Poundland !
I have one of these. Also had the problem of batteries discharging even when the light is not in use. It's due to a design fault. There is a lug under the slider which lifts a metal strip off the contacts on the PCB when the slider is moved to the 'off' position. However the slider is a loose fit in its housing, and when you take your finger off the slider there is enough spring in the metal strip to move the slider within its housing so the metal strip goes back on to the contacts. Evidently some current passes, even though the LEDs don't light, so the batteries get discharged.
The solution is easy. A pin through the soft plastic to hold the slider snugly within its housing – 5mm of an ordinary dressmaker's pin with the point snapped off. Works a treat.
Also I am running it with 2 alkaline batteries i.e. 3v rather than 4.5v, which I hoped would take some strain off the LEDs at full power, and perhaps lower the temperature of the transistor at medium setting. It is still plenty bright enough on 3v. The third battery slot is occupied by a bit of steel rod sheathed in plastic from an old ballpoint pen, roughly the same diameter as an AAA battery. Or one could solder some wire across the terminals. I don't know much about electronics, or how the calculations pan out at 3v. Can anyone help? I assume the steel rod has less internal resistance than an AAA battery. Would it still be sensible to put a 22ohm resistor in series with the LEDs, or perhaps a different resistance?
After watching this video I bought a couple for my students to experiment with. They made a simple amplifier and used the slider to set the bias. The COB led worked great when connected to a 555. Lots of fun education. Thanks.
Big Clive; turns it on THEN tears it apart.
Next video: Add a 555 timer dimming circuit to this so called “very dodgy” dimming circuit.
don’t forget to shout out
I have that very stick light, and highly recommend it, especially for £10 on eBay 👍🇮🇲
I saw one of these at a Hardware Sales store near my place just down the highway.
They are actually kinda cool.
Clive I think you did a battery video some time ago and I just don't recall when. What I am looking for is the best NIMH D batteries that I can get. Do you have any that you recommend or a video you can point me to. Thanks Sean
I have got one but the battery's wear out over time 🙁
There is a Dealz in Torremolinos too! It is odd to see what is very much a Poundland but in Spain!
Uhm…. I don't think "poundland" means what you think it means. But at least it brings in the views.
£2 to buy… £30/Month for the Batteries…
Now I will have to come to the UK just to visit PoundLand.