convert 5-mode CX2817-based driver to 3-mode

Flashlight Modding and DIY Parts
1

I just received a 2-cell zoomie that I bought from ebay and took it apart right away.

I found the same driver shown by RaceR86 from this post .

A quick search found this datasheet for the cx2817.

The datasheet describes two modes: Mode 1 with High/Low/Flash and Mode II with High/Medium/Low/Flash/SOS. Pin 2 is used to select the mode. From the picture of the driver, it looks like pins 2 and 3 of the CX2817 are connected to the 0 ohm shunt resistor to its left. I removed the shunt and the light now works with three modes instead of five.

It’s an easy mod until I can get my hands on a better 2-cell driver.

2

I forgot to mention that the shunt can be easily removed with needle nose pliers.

3

Awesome…good job!

Is that one of the drivers you have to go thru all the modes to turn it off?

From the other thread it has next mode memory

Could the pencil lead trick on the capacitor next to the CX2817 work?

4

No, this driver is for clicky switch not digital switch. I haven’t tried it but the pencil lead trick should work since that cap provides backup power to the chip.

5

Pencil lead mod confirmed to work. I bridged the capacitor to the right of CX2817 in the above picture with pencil lead. The first attempt resulted in a 1-mode switch because I put too much. The second attempt resulted in loss of memory after 1 second. Now I have a light that turns on in High mode every time.

6

Maybe someone could chime in here

Since you could solder, you could put the flashy modes back in then put a resistor over the cap, I notice depending on the humidity my pencil lead mods sometimes work faster or slower.

Anyone know a the resistor amount to get a good 5 second reset (physically solder a resistor across the capacitor)
I think I read someone said something like 200K or something?

7

I detest blinkies. Having to cycle through them with next-mode garbage drivers is why I do NOT buy more of that crap.

The few garbage driver lights I have are now tolerable, thanks to the simple pencil mod. I have mine reset to HI in approx 0.5 second. That’s fine with me. And I didn’t have to microscope-solder teensie chip resistors.

In rough numbers, I remember my penciled resistance around 300Kohm. Maybe 250Kohm-350Kohm. From salvaged laptop battery packs, I pulled some resistors in this range, and sent them to a buddy. He never used them.

8

That’s generally where I like to end up, probably in the 0.5s to 1.0s range. 5s does not make much sense for mode switching IMO, even 2s is a long very time in that context.

I think the required resistance will vary between applications although I’m not really sure why.