r/Electronicsinindia

First time finally soldering after watching loads of videos online.

Looking for critique to get better.

Just got Themisto TH-M100 and it looks sooo sexy

Hello everyone,
I studied in a technical high school where I studied electronics as the main subject in my 8,9&10.

I was fascinated to learn about Resistors, capacitors and all other components. I even learned to solder and make half/full bridge circuits.

Then I took commerce in 12th and didn’t really get a chance to do electronics again.

Now I’m my 30s and I’m trying to spark that interest again. Spending my adult money on things I wanted.

I only learned the basics and not about microcontrollers. Now I work in IT and I’m trying to combine my coding skill with electronics.

I ordered the soldering kit, some breadboards, wires, ESP32, capacitive moisture sensor.

My first goal/mini project is to make a moisture meter for my indoor plants. Read the data, send it to RaspberryPi over wifi and make a dashboard about it.

Order the above items from Robocraze.
Multimeter from Amazon
Moisture sensors (not in this pic) from Techiesms

Wish me luck!

I have an Arduino Uno (7–8 years old) and a fairly new ESP32 WROOM, but I currently have no other components(not even a breadboard or LEDs).

What is the most cost-effective way to learn as much as possible about electronics, microcontrollers, and these boards with the minimum number of components I need to purchase? My goal is simply to understand how things work and experiment hands on, while keeping the total cost as low as possible.

Approximately 2 years old, used only a couple of times. It hasn't been used much!

Including case and vent fan, the asking price is 6k (negotiable).

Location-hyderabad.

It's sold!

If you haven't checked out my review and testing post for this light yet, take a look here first:

https://www.reddit.com/r/Electronicsinindia/comments/1vf7f0w/actually_a_really_good_and_repairable_product/

Disassembly & Housing

The teardown was relatively easier compared to lights from other major manufacturers. Accessing the main driver PCB requires removing 6 Torx screws, torx are used as they reduce head stripping during maintenance and make factory assembly easier.

After removing the screws, the side plate requires prying because it is glued down with a waterproof sealant/gasket compound. Prying it open will of course fuck up the factory IP waterproof rating on the side panel ( T7000 glue could be used to reseal it).

Unlike the front bezel, which uses a traditional rubber O-ring seal, the side cover uses a sealant. This is likely due to perimeter size: the front bezel has a much smaller perimeter (~11 cm), whereas the side cover has a much larger perimeter (~23 cm) where compression on an O-ring is harder to maintain.

Note: the front bezel screws are of different size than side panel

To fully remove the PCB, you have to desolder the auxiliary/sense contacts. Beginners should take extra care here to avoid damage to the small SMD components (marked GL FT) situated near these pads. Further teardown requires additional desoldering, which I did not do as it isn't necessary since the PCB is primarily single sided.

Switch Mechanism

The rotary dial switch does not mechanically lock out the light as I initially thought, rather it’s a pretty interesting electronic switch with no physical contact with the main pcb

It uses Hall effect sensors built on the PCB itself triggered by weak magnetic fields inside the dial. The magnetic field is kept intentionally subtle so it won't attract other iron stuff, but it is strong enough to trigger the sensors.

There are two very small ICs near the hall effect sensor marked as GL FT (ones I mention earlier), these are the actual Hall effect sensor ICs/Hall effect latch.

Power Stage & Inductors

As suspected in the review, the driver uses switch-mode regulation:

• 10 micro henry Inductor (100) smaller size : is for the USB-C charging of the Li-ion battery.
• 0.47 micro henry Inductor (R47) larger size: for the main high-power LED driver loop.

The main LED driver operates at a much higher switching frequency (cannot measure exactly as I don’t own a oscilloscope currently), so it to uses a lower inductance value to deliver continuous high current without saturating the core.

Both inductors are resin-molded/shielded inductors. These have significantly better drop resistance than open wire ferrite core ones where a single impact can damage the core as some of you might have noticed

The molded ones also have better suppression for the high frequency audible switching noise.

Microcontroller & Driver Logic

The main controller is an FMD FT61E0A5 8-bit RISC microcontroller.

Almost all flashlight manufacturers use general purpose MCUs rather than dedicated ASIC (application specific ic) controllers. Using an MCU brings distinct trade-offs:

Pros:

1.  UI Flexibility: Allows custom UI modes and thermal regulation logic. Since the control is software-driven, Wuben could technically add features like stepless ramping in future firmware revisions.

2.  Cost & Repairability: Cheaper overall manufacturing costs and standard microcontrollers are easier to source and replace if damaged. (Note: The FT61E0A5 on this board does not support flashing over USB since the USB port is wired for charging only, so updating firmware requires direct programmer pads on the PCB).

Cons:

1.  Stability: MCUs can sometimes freeze or glitch under high noise or low voltage states which is why few medical devices pair MCUs with dedicated hardware safety supervisor ICs.

2.  Quiescent Current: MCUs draw continuous standby/sleep current which matters more on a light like this that lacks a mechanical physical lockout switch, that said this particular micro controller advertises very low current draw just 0.2 micro amps

MOSFETs, Battery Sensing & Hardware Details

• Main Switcher: The primary power MOSFET is an SA4456 (N-channel TrenchFET in an SO-8 package, equivalent to AO4456/Si4456).
• Interconnects: Battery power transfers to the PCB via a flexible ribbon cable rather than discrete wires. This keeps the PCB flush with the body, though ribbon flex joints are more delicate during repeated teardowns I think wuben could have designed the housing a little differently and used wires instead
• AAA Sense Logic (unsure): The small GL FT , GL  (LDO/voltage detector) and FT (signal switch) ICs manage the dual-fuel input detection when using the 4x AAA cartridge Telling the MCU to limit output power of the light for standard AAA cells and also disable the charging port. This confirms the proprietary Li-ion pack doesn't rely on a complex communication bus as I initially thought this also makes future custom battery replacement much easier. [ I am unsure about this as there is no info about these ICs on the internet apart from the general i mentioned, there also appear to be no connection between the auxiliary points (mentioned earlier) and the battery contact of the AAAs I would need to confirm this with Wuben. My best guess for now is internal resistance dependent battery detection]
• AAA Sense Logic: I confirmed with wuben and they told me it's a simple voltage based detection. Basically when in series the AAA (fresh) have a total of ~6v which is off course higher than max voltage of the 3.7v battery (i.e 4.2v). The GL FT ic are actual hall effect sensor IC I forgot that A LDO would need few config resistors and capacitors for the output so yes they are the sensors.
• ⚠️ Does this mean when we put fully discharged AAAs it does not detect properly ? ---> No , it does detect properly as AAAs and AA recover a bit of voltage after being fully discharged to around 1v , after recovering they sit at around 1.2v and the flashlight successfully detects that as I tested and confirmed it.

The connections are also gold plated for better rust resistance

Other than this there are couple of more ICs that handle actual switching after getting the signal from the microcontroller , few smd capacitors and few current sense resistors etc

Overall, I will give it a 8/10 for the repairability , two points deduced for the ribbon cable and required desoldering at the auxiliary connections

Wuben release assembly videos for all their lights and this gives me the confidence the brands cares about the repairability - https://www.youtube.com/watch?v=aC9J28Dku08

Also one other good thing is that they have not erased any of the marking that are there on the semiconductor  

Few thing that I forgot to mention in the review post-

• Machining: The body is CNC-machined/milled aluminum rather than cast alloy, having better tolerances and better finish
• Pocket Clip: Constructed from stamped spring steel rather than aluminum to handle continuous flexing without snapping.
• HVAC Utility Note: A professional technician I know pointed out that pairing a UV LED with a red laser module is extremely useful for HVAC leak detection where fluorescent dye is injected into AC refrigerant pipes, and the UV beam illuminates exact pinhole leaks.
• Charging: the light can be used while it is plugged in through the USB-C port eco,low,medium mode can be used this is quite useful for obvious reasons

Overall, it's a very repairable flashlight I hope Wuben considers selling replacement PCB modules directly for users who want to repair on their own

Any ideas where i can find this board ?

I need components for final year project...If possible can anyone please share any geniune electronics components dealer in delhi ncr or any geniune website for same.

I want to test the capacity of few of these, so I thought I would better ask and get some average number

I personally have seen multimeters stop working at 6v but also few devices like calculators at 4v or 5v

Currently on the test list is Hi-waat , eveready and nippo , if you want me to include any other feel free to drop the recommendations in the comments I will try to include those