Updating the SK58 to e-switch - 2016 version:
The Sipik 58 is a small 1xAA sized zoomie very similar to the well known Sipik 68. I prefer the Sipik 58 because it is thinner and its more streamligned design feels much better in the pocket and hand. Recently I modded an SK58 to use an LED Lenser style lighthouse optic. See my build thread for that mod here .
Tailcap e-switch build thread
This thread discusses how I installed a tailcap e-switch in that SK58. I considered adding this as a post in my previous build thread, but this build is complex enough I felt it deserved its own thread. This is somewhat similar to an e-switch mod I did on an SK58 five years ago. However, this 2016 mod gains the benefit of everything I’ve learned since then and should work much better.
Why I like e-switches
I prefer e-switches over mechanical clickies. E-switch drivers allow for a more intuitive UI than a clicky. With an e-switch and proper driver you can have shortcuts to moonlight and turbo. They’re also much quieter and tend to have a softer touch without as much travel in the switch button.
With a conventional mechanical clicky switch main current flows directly through the switch. Flipping the switch cuts the power completely. In contrast, an e-switch is simply a momentary pushbutton attached to a circuit board. Main current flows through the circuit at all times. The button is simply the input telling the ciruit what to do. Main current does not flow through the e-switch, so the button and its associated wiring can be much smaller than with a clicky.
The downside is you can’t just swap in an e-switch in place of a clicky.
Here are the common ways I’ve seen e-switches in flashlights:
- Method 1: E-switch Driver in the head, eswitch in the side of the head. By far the easiest method. With the switch and driver right next to each other, wiring the switch to the driver is easy. This is the most common type of e-switch found in LED flashlights.
- Method 2: E-switch Driver and switch in the tailcap. Not sure exactly how this works, but I understand it involves reversing the battery so (+) faces backwards. Many budget Costco lights with tailcap e-switches use this method.
- Method 3: Clicky-switch Driver in head, separate circuit with FET and switch in tailcap. This is the only type of e-switch that is interchangeable with a clicky switch. Downside is the circuits are virtucally impossible to find (I have 3 leftover I purchased from Steve Ku at Veleno Designs 5 years ago), they might not be able to handle a lot of current, and because they are using a clicky driver you don’t get the great UI only possible with an e-switch driver. The separate circuit also requires its own power supply to operate, usually a tiny coin cell battery or capacitor.
- Method 4: E-switch Driver in the head, switch in the tailcap. Think of this as basically the same as a sideswitch, but with the switch slid over to the tail. The switch itself needs one end connected to ground and the other to have a dedicated insulated connection back to the driver. Installing that insulated connection and having it work reliably through battery changes is the tough part. Both HDS and Liteflux lights use this method for their tailcap e-switches. HDS uses a stiff wire in a trench in the side of the tube. Liteflux used a thin metal tube inside a thin insulating tube all inside the battery compartment.
For this mod I selected Method 4: E-switch Driver in the head, switch in the tailcap.
- Step 1 - Driver update. The driver is the same 15mm FET driver from Mountain Electronics I started with, but now with moppydrv e-switch firmware. The topside of the driver has 2 bondpads for the e-switch wires. One of those pads goes to ground so I can ignore it. For the other pad, I drilled a tiny hole all the way through the driver in a bare patch and ran a thin wire through it. One end connects to that pad, the other end connects to a copper ring. The ring is sized to be as wide as possible without touching the sides of the body tube. I insulated the bottom of the head with arctic alumina (AA) before using more AA to attach the ring to the driver and head. Here is a picture of the underside of the driver before I glued the ring in position:
- Step 2 - Tailcap construction.
The Sipik 58 tailcap internals are very similar to the SK68 or other cheap lights: Basically just a press fit plastic retaining ring holding a cheap clicky switch in position. This needed to be completely replaced in the e-switch build. I needed to construct completely new tailcap internals containing the following:
(1) a direct connection from the side of the tailcap to the back of the battery, bypassing any switch. This connection needed to be quite firm, with considerable pressure applied.
(2) a momentary pushbutton switch, with one end connecting to ground, and the other end connecting to…
(3) an insulated contact on the battery compartment end of the tailcap. This connection must be insulated from ground. It cannot touch the sides of the tube, tailcap or back of the battery. However, it must be able to contact the insulate connection passing through the battery compartment from the head of the light.
Since the rings on each end take up some space, I free up a mm or two by filing off the tip of the tailcap threads.
I’ve had trouble in the past with the switch mechanism not always having a firm connection to side of the tailcap. This time I decided to use a spring from a Nanjg 105c facing sideways into the side of the tailcap. I started by constructing a housing for the spring. Here’s a pic of the tailcap and the housing with spring installed:
Another pic with housing inside the tailcap:
Then I added a cover plate on top of the housing:
And a post to touch the back of the battery:
Except for the spring, so far the entire housing is made of copper and is all soldered together. Electrical connection to ground is excellent.
I removed the housing and turned it rightside up. I drilled a hole through the entire housing for the switch wire. I used superglue to glue a microswitch to a thin piece of plastic sheet and then to the top of the housing.
I ran a small piece of thin teflon wire through the hole. One end connects to one of the switch legs, the other to a ring constructed just like the one at the head of the light. To connect the switch I used conductive silver epoxy. After that dried, I protected the epoxy and wire by covering it and the area around the switch with a fairly thick layer of arctic alumina.
Here’s a picture of the switch with the ring dangling before I glued it down. Note the AA on the underside of the ring to insulate it from the housing:
And a picture with the ring glued down:
For electrical connection from the head to the tail I cut a piece of plastic sheet (thin sheet from local hobby shop) into a rectangle and then bent it into a tube. I did the same with a piece of shim brass. The plastic insulates the brass from the body tube, while the brass surrounds the cell and touches the rings on each end of the tube. I also bored out the tube so the interior of the tube had much more space.
Here’s a picture of the tube, you can see the brass. The light grey touching the brass is the plastic.
Connected it up and it works! Switch pressure wasn’t quite right so I disassembled the tailcap and swapped in a different boot with some rubber and plastic inserts to get just the right soft touch. Much better.
Additional mods I may do to this light:
- It works well now, but both sleeves are slightly small and don’t make a complete 360. Might be a good idea to redo the sleeves and clean them up.
- Without the sleeves the light can fit a 900 mAh Efest IMR 16500 cell. Perhaps if I grind a trench down one side of the compartment I might be able to add an insulated strip of brass to connect the rings. It would be nice to upgrade from 14500 to 16500 for extra capacity.
- Bezel cleanup. Current bezel I’m using now is aluminum with some epoxy. Decorative aluminum ring on the front should be redone and optic remounted and recentered.
- I might try Birchwood Armory aluminum black on the bezel. Never tried this stuff before but I received some this week. The list of toxic ingredients looks kinda scary though!