Mod/Driver: ZY-T08 series conversion, MT-G2.

This light has been one of my longest ongoing projects. I’ve almost quit it a few times but I like this light for mine/cave exploration and I’m too stubborn to throw in the towel. Now I think I’ve got it right… The original post about this mod/driver has been moved to post #2. The light and driver has gone through multiple changes since then.

The latest version of the driver (called v1 again as this is what I consider to be the first releasable version after many different versions).

Differences from the original version in post #2:
Switched MCU from ATtiny84 to ATtiny85 as OTC, E-switch and voltage monitoring on the same pin has been tried and tested, allowing me to use my standard firmware.
FET for boost. Slave board support no longer needed and has been removed. This driver is essentially just a larger version of my F8 driver: Driver: F-8 v2 (17mm FET driver with 8 x 7135)
5v LDO, zener diode and resistor no longer needed.
Ground ring removed as this, among other things, was causing shorts when screwing the light together with cells inserted.

Driver layout:
The FET is maybe a little to close to the MCU. The MCU can be flashed with everything in place (wires included) but it’s a bit finicky to get the clip on the MCU. If I make an update I’ll move it a little.
I put solder pads on the top side so that the FET can be activated by either PB5 (reset pin) or PB3 (string of 4 x AMC7135).
I kept the possibility to choose the zener and resistor solution by placing the footprints for them within the LDO footprint.

The biggest issue I had was with cells getting shorted with stiffer and longer springs. Removing the ground ring on the driver helped, but with the edge of the head rising higher than the pill I could still get shorts with some cells, at least the ones that have the entire bottom of the cell bare.

I solved that by filing the edges of the head down to the same level as the edge of the pill. I still prefer cells have about 1mm of wrapper in from the edges for added safety in this light though.

This is my only driver with the MCU on the inside. I made one version with the MCU on the outside, but building some sort of clearance ring so the cells could screw on turned out to be too much of a hassle so I just put a hole in the top left part of the driver so it can be removed easily.

The clip fits over, but it’s tight:

I had issues with the previous switch freezing after getting mud on it, so I installed a IP67 sealed switch instead of the small little thing I had taped on the outside before. I just drilled out a much larger hole for it.

A little bit of glue to seal the hole so there should be no issues with water getting in.

So I think I’m done… but I’ve thought that before… It’s coming with me on my next trip down into a mine so I guess I’ll find out…

I’ve had a ZY-T08 lying around for awhile and had a previous go at modding it to run my current favorite emitter, the 5000K MT-G2, and a side switch (it’s too big for my taste to handle without): Mod: Small Sun ZY-T08 MT-G2 (without cells in series conversion)

It was a nice try, but how I hated that driver! Mode changing was sluggish and output wasn’t where I wanted it to be, so back in the drawer it went. However, ever since I made my first driver for my triple MT-G2 M6 build I’ve kept the ZY-T08 in the back of my mind. Now I’ve finally gotten around to doing something about it.

I wanted to run any number of AMC7135s on in constant current, so I made a master/slave board driver configuration and used the ATtiny84 with it’s 12 IOs so I can turn on any number from 1 to 31 AMC7135s, have an E-switch, off time cap and voltage montoring. I put so many AMCs on because I had room, and am curious to how many I can run on constant current.

I wanted to be able to screw apart the light as normal for cell changing so I didn’t put components on the back. I put all wire vias in the center of the driver between the cell contacts to prevent wearing and shorting when screwing the light togther/apart. As springs wouldn’t work I built up solder blobs as cell contacts. While I was at it I made a tail-switch board with holes to match up with the large rectangular Omten switch. I had to file down the corners of the switch a little before it fit inside the tail-cap.

Tail-switch board shaped for a perfect fit into the host:

While I was working on the user programmable modes interface I got the idea of making the output fully adjustable from moonlight to full blast with smooth seamless increase. So v3 was born. It has an additional AMC7135 dedicated for PWM, so not only can I turn on any number of AMCs for 0.35A steps, I use PWM in-between these steps so I can basically get any output level I want.

Assembling works great. The driver insertion into the pill had to measured out so the cell contacts on the board line up perfectly with the cells when the host is fully assembled. I made the driver board slightly larger in purpose so I could file it down for a tight fit into the pill. It won’t budge, so it feels safe. The downside is that it’s hard to get out, so I had put off assembling this light for a long time as I wanted working firmware in it. It’s not finished, but sooner or later I had to put it together to make sure this series conversion idea actually worked. A hole to assist pulling it out might have been a good idea…

I’ve done a temporary E-switch installation, just to try it out. I want to make something similar to Old-Lumens side switch solution: SS ZY-T08 5-up Mod - Finished but first I needed to test the light a little first before working further:

Current firmware details:

  • Three operation modes. Using terms “mode” for mode of operation, and “level” as output level (referred to as “mode” in most lights).
  • Mode 1: Short E-switch press for next output level, long E-switch press for previous output level. Boost is activated as any other level.
  • Mode 2: Short off-press with tail-switch (off time cap) for next mode. Boost level not selectable by level change though, it’s activated with the E-switch from any level. Releasing before 2 seconds deactivates boost (good for signalling to climbing/mine exploration buddies). Hold longer and it locks on so E-switch can be released. Boost will then continue to run until turned off by another E-switch press or timeout, then revert back to level the light was in before boost.
  • Mode 3: Fully adjustable output level, from PWM off a single AMC7135 to all AMC7135s on. Holding E-switch increases, double press and hold on second decreases. Output level is smoothly adjusted with PWM between the 0.35 constant current steps, using an algorithm that increases steps as output level is raised, giving the illusion of smooth linear adjusting from moon to full output.
  • Mode 1 and Mode 2 share the same three programmable levels (and boost), Mode 3 has it’s own independent level.
  • Medium off-press selects next operation mode. Short blinks indicates which mode is activated.
  • Low voltage steps down levels normally in mode 1 and 2, halves output level in mode 3.
  • Several functions activated by holding E-switch on startup and counting blinks: Level adjusting mode, voltage readout, temperature readout, temperature controlled mode (experimental), safety lock, on/off when critical voltage level, reset all levels & settings to default.

The temperature controlled mode is so far just in testing stage to blink out certain patterns when the temperature increases or decreases when in mode 3. I’m playing around with it to get a feel of how it works, how long time it takes to sense heating and cooling on various output levels. I also have to consider that if I do any mods to heat handling I’ll be changing the characteristics and will have to adjust the code.

The level adjusting mode works as Mode 2 (short off presses to change levels) with the difference in that the E-switch is used to adjust current level up or down (as in Mode 3). Times out after 5 seconds of inactivity, returns to normal operation.

The light is working and so far I like it so I’ll continue to develop it. The different modes of operation are inspired by thoughts I’ve had on using lights during underground exploration. We’ll see about the temperature controlled mode in this light because making changes to the firmware and then testing in the light is a PITA as I have to rip the whole thing apart and unsolder/re-solder the E-switch. I might just implement an overheating protection that simply shuts it down until a specific cooler temperature is reached and save the temperature controlled mode for another light with easier MCU access.

As I’ve tested the light and like it, V5 is on the way (v4 got scrapped). I’ve added a footprint for a FET. Thanks to the 12 I/Os of the 84 I’ll be able to choose to use a FET or slave board, or both.

Nice work again, Mike :beer:

You are doing some great work with the driver development, & I'm sure a lot of people on here would like to utilize your creations.

Thanks. It was when writing this firmware I really took a liking to the dual switch approach, hence my thread asking for them. I’ve got an idea on how to use this seamless level selection on a 17mm driver with 8 x AMC7135s and a FET, and put it into a small triple XP-L HI. This is why I was interested in yours :slight_smile: I’ve got an idea that’s a little different than yours but should work, the driver boards are designed and ordered.

Been thinking about this a little. Problem I’m currently having is that I always seem to have the next version on order before really finishing the existing version. Just when I think I can’t cramp anymore functionality in I come up with some must have feature that gets me all crazy. Like this seamless level thingy, once I started liking it I couldn’t stop myself and now have new driver boards for my triple M6, headlight project, 17 and 20mm drivers, all waiting for new firmware… the frenzy never ends.

Enjoy the hobby :beer:

Would you please link the PCBs?

This light is one of the lights I don’t have (yet) - and with this mod and a MT-G2 laying around here, this is even more interesting!

DO you know what the max. LED PCB Diameter could be? My MT-G2 sits on a 25mm copper disc.

Thank you!

Not quite ready to share this yet. Also, the MCU on it is the 12 pin ATtiny84, and I’m not quite ready to share that firmware either. Depending on what features you want I might be able to offer you one, depending on what functionality you want. I always get three boards from OSH Park and therefore have a few of each version left over . There is however someone waiting in line (who has been waiting for a long time) who gets first choice amongst the boards that I have left.

25mm MCPCB is what I have in mine and fits nicely, it’s the largest that will fit. The solder joints will interfere with the reflector, so they should be as low profile as possible and the reflector needs to be isolated so it doesn’t short the wires.


I only need the rear switch - I will use a zener modded Nanjg Driver :slight_smile:

I can certainly share that one:


Awww, darn. Have you heard this saying? :slight_smile:,\_release_often

I really want to do a series conversion with a custom driver like this…

Is there a reliable source for quality T08’s? I know RMM stopped carrying them because the quality went way down.

I hear you. Gotta try out the new version with the FET first though.

I got mine ages ago, so I don’t know myself.

Light and driver has had a major overhaul… again… Details in OP, original post moved to #2 (yippee, I found use for that reserved post).

Do you have a link to the switch you used? I’ve been trying many things, but have yet to work out a good switch housing when adding an eswitch to a light.

Mike, please give your suggestions about copper pill design for this light.

Nice work! I have one and have a few ideas about it. The tail switch would break contact between the cells rather than between the host and 2B~~. Leave the existing contact board in the head as is and make a new oval one to fit in the head end of the battery tube with solder bumps on the top (both at 2B+ potential) and copper tabs at the ends to ground the host that get sandwiched between the head and battery tube. On the underside of this board are a B+ and B~~ contact. This way the rotation of the battery tube is irrelevant to polarity.

I knew you had reserved a post for a good reason :wink:

I’m not sure how I missed this one. Nice work. I’ve been playing with this light myself lately having made a couple with the batteries in series. Is there a link to Oshpark for the switch board?

Yeah, I’ve had some issues with that too. This is the switch I used for this light:
For smaller lights I did this: Mod: My take on the convoy S series with side switch mod.
Check the last photos, I ditched that switch that was taped to the outside.

I would definitely like a copper pill for this one, but the light I have is quite old and I’ve read here that the newer ones have declined in quality. Someone would have to confirm though. If the new ones suck it might be a waste of time making a copper pill for it.

I’ll have to make it a habit now, I’m hooked! :smiley:

I had one shared before, but changed the design just a little later on… I’ve now shared it again: