Overview

Six LEDs in two parallel strings each of three LEDs, running off a 12V battery.

Battery

Drop-in conversion. 1.5V N cell replaced with 12V battery (MN21, G23A, A23 etc – the sort that powers car alarm remote control units), which is about 1mm shorter and narrower than the N cell.

Bulb

Drop-in conversion. 1.5V, 200mA incandescent bulb and reflector replaced with custom-made 6 LED circuit board.

Notes

The positive contact of the circuit board is right in the middle on the opposite side to the LEDs, so it contacts the positive tip of the battery without any need for extra spacers or springs. The negative contact works off the switch action in exactly the same way as the original bulb holder.

The LEDs are a new item in the Jaycar Electronics range, which require a significantly lower operating voltage than any white LEDs I've seen before. In other words, more light from a tired battery – just be careful when it's new.

Because both changes are simply drop-in replacements I can change it back to show off the difference very easily. In the photo the ring of six LEDs can be seen at the front, but that and the slightly skinnier than standard battery are the only signs that it isn't stock.

One reason for having so many LEDs is to provide a reasonable light even when the battery is quite flat. This is possible because the colour of the light that white LEDs make does not change (very much) when they are run at low currents, and because LEDs run with low currents are slightly more efficient than when run at moderate currents. So twice as many LEDs running at half the current gives better light. It's more expensive, though...

FWIW the number 4000 in the torch's name comes from the number my digital camera was up to when I took photos of the finished LED torch.

Aside: "Torch" vs "Flashlight"

Philips (as in Royal Philips Electronics) has this to say on the history of the strange-seeming American term:

In the early days, people were only allowed to use their flashlights for only a few seconds because of the inefficient carbon filament bulbs and weak batteries. Consequently, these brief flashes of light resulted in portable lighting products being named as "Flashlights".

Results

Before Conversion (new battery)

I saw it behind the counter – a cute little transparent purple torch, looking like it was in the same series as my three LED torch*. It came with a 1.5V, 200mA incandescent bulb, powered by a single N cell. It clearly would never give satisfactory performance – I don't know why people bother sellng torches like this.

*Red transparent coloured body to fit a single AAA cell, similar black business end.

It was also clear that I could give the poor thing its only chance at greatness it would ever have. So I bought it, and started making plans.

Before conversion: Output with new battery.

Comparison with 3 LED Torch (flat battery)

As I said, it's a cute little torch, and it's full of promise. The diameter of the front window is greater than my old favourite three LED torch, so it has the potential to be even brighter than that torch.

This was how my three LED torch performed with a semi-flat 12V battery. (Non-loaded 9.6V, loaded ~8.5V @ ~5mA.) So I've now got a benchmark.

Comparison: Three LED torch output with semi-flat battery.

6 LED Torch (flat battery)

My new torch performed rather well. This is how the thing worked with the rather flat battery taken from my three LED torch. (Non-loaded 9.6V, loaded ~8.3V @ ~6mA.) Brighter and whiter, for hardly any more current. I think I might have a new favourite.

After conversion: Output with semi-flat battery.

6 LED Torch (new battery)

And definitely a new favourite with a new battery installed. At least 1.1W when it was first turned on, although that dropped pretty quickly – poor battery. So, a 1.1W torch which measures just 48mm long (56mm long including the keyring loop). But try getting an output that even and smooth with a mini Maglite.

In case you're wondering, that beam centre (almost a third the width of the photo) is completely over exposed.

After conversion: Output with new battery.

November 2006. Sadly, the ianman4000 was lost at the end of August 2006, along with the purple carabiner it was attached to. Possible locations include a friend of a friend's place somewhere near Pukekohe after a possum shooting trip and Middlemore Hospital while visiting a sick friend. After two years of good service, I'm sad to see it go. (Actually I didn't see it go, which is even sadder, since I don't know it's in a good home.)

Onward and upward, though. I'm planning a new torch that will use a 1 watt star LED instead of 6 individual 5mm LEDs, and will be powered by a 6 volt 4LR44 battery (aka 476A, A544), which is just four LR44 cells (aka A76, aka AG13) in series. Testing of the star LED has produced satisfying results, and the star heatsink can get quite hot over 200mA.

While trying to find a replacement torch body to modify I've managed to find out that the ianman4000 body was probably a Dorcy torch (Dorky torch? Dorch? Or is it pronounced "Dorsey" to rhyme with "horsey"?). I've seen a different N cell powered Dorcy model in a local hardware shop, so it seems it may be available somewhere. Sounds promising. The hunt is on.

In the meantime I've bought a 3 LED torch from a $2 shop. It's powered by just three AG13 cells. I've already checked that a 12V A23 battery fits, although the back cap doesn't screw on completely. I guess the spring takes up a lot of the slack. It looks like there isn't enough room for a 6 volt 4LR44 because of the extra width of the battery jacket holding its LR44 cells together. The torch's switch can operate momentarily or push-on/push-off but is quite easy to operate – I can imagine it would easily get pressed in my pocket. The torch is reasonably bright with fresh batteries so it'll tide me over quite well until I can find another Dorcy of the right sort to modify.

Update Jan 2007. OK, I didn't count on the 8.5 year old nephew who quite liked it. It turned out the switch was too easy to turn on in my pocket, so I'm not too upset to see it go.

Update Oct 2007. Yay, I've found a new source for these things, in orange, blue and green. [Later in the month:] And purple!

Update 27 August 2008. It's back! And it's purple! The ianman4000 mark 2 is now in operation, using a single Cree XR-E P4 running directly from four AG13 (LR44) cells. I gave up on using an 4LR44 because it's just a little too wide to fit. It's also a fair bit longer than four individual AG13 cells. At the moment the cells are taped together, but I don't think they need to be – they would be fine being loose. (I later decided it's too fiddly if they're loose.) With fresh cells the Cree draws 320 mA and the TIR optic throws a very nice beam. A very pleasing result, and with a silicone glowring (glow in the dark o-ring) just behind the head, it can be found in the dark.

Update 2 September 2008. Um... well.... I don't have it any more. I gave away the guts in another keyring torch. The ianman4000 mark 2 is now orange.

Update 22 September 2008. OK, now it's back (my keyring torch, that is, not the mark 2 which is still orange). With a Cree XR-E Q5 LED it's very bright, very portable, and has an improved, simplified design over the mark 2. It's the ianman4000 mark 3. Fresh cells gave an initial current of 360 mA, although that was heading downhill pretty fast. But even with less than 150 mA with a slightly tired battery it's impressively bright, and it still has that great beam from the Cree 8° TIR optic. (TIR = total internal reflection.)

Update 2 & 10 May 2009. The LED of the orange mark 2 has now been used to provide a backlight for the screen of a radio and a Cree Q5 has been put in its place in the orange torch, thereby upgrading it to a mark 3. Even so, the owner reports that with the Cree P4 he had one of the brightest torches at a recent camp he went on.

Update 13 May 2009. There are now three ianman4000 mark 3 LED torches in existence, in purple, orange and green, each sporting a Cree Q5 LED. Converting the green one today took about an hour and ten minutes – it's quite a fiddly process and I trimmed the back end of the optic holder a fair bit to make room for the wires which I soldered directly onto the LED (not the board). I also had to insert the TIR optic into its holder a second time as it wasn't quite straight so I wasn't quite happy with it.

The percentage improvement in brightness this modification makes to these torches can no longer be measured in percentages: It's infinite, since with the old N cell the original incandescent lightbulb was drawing 250 mA but making no light at all! The LED also draws 250 mA from its four LR44 cells (when they're newish) but makes a very impressive amount of light.

Update 15 September 2010. My ianman4000 mark 3 LED torch was stolen on Saturday 11 September from a locked car at Twin Bridges, Northland. It's the purple one in the above photograph, and had a small purple carabiner attached. A reward is offered for its return and information leading to the arrest of the pond scum that stole it and the other items taken in the same incident.