Cheap Flashlight/Tazer combo Teardown
I had a friend lend me two for repair. These are chinese cheapies with dubious quality and safety issues.
These have internal non replaceable batteries and is charged directly from the AC mains with an AC plug at the back.
A slide switch on the body to select tazer or flashlight mode, and a push button to enable the tazer. A small slide switch at the back acts as safety so the tazer doesn't go off in your pocket.
The pair of flashlights. Both are broken.
The flashlight head is plastic and the crown has the metal contacts acting as the spark gap.
The tail cap contains some point to point circuitry. This is just a basic capacitive dropper circuit to charge the battery.
With the head removed, we see a mess since the cheap ni-cd cells have leaked.
The electrolyte has eaten the reflector coating so it is now clear.
The reflector is heavily damaged by the cell leaked electrolyte.
The battery pack is composed fo four 2/3AAA cells in series. There is a tap so that the LED runs off of 3 cells. The tazer runs on four. There is no LED driver, current is limited only by the cell internal resistance and thin wires.
Insulation? We don't need no stinkin insulation.
Keep in mind the whole circuitry is live when charging through the AC mains.
If that bare wire touches the metal case, then....
Here is the capacitive dropper circuit. It uses a 400V 680nF cap but no inrush limiting resistor.
Most of the space inside the flashlight is taken by this long black tube. It contains the high voltage inverter to create the sparks.
Connected it to the bench supply and it still works. Draws over 3A at 4.5V.
The sparks are loud and scary.
Now, if it draws over 3amps, and the tact switch that switches the power to it is rated at 50mA, you guessed it, it melted stuck. That's why one is broken.
The other light is similar except that it used only three cells.
The LED star heatsink says "FULL MOON". Yeah, OK.
As I have suspected, to fit a flashlight and a tazer in one package, something has got to give. That is why I never looked at buying one of these. I still prefer a standalone unit. If you have one, never touch the light when charging as it is a big electricution risk. The tazer contacts in the front are isolated from the mains input when measured using a DMM but I wouldn't take chances especially with the insufficient (LACK OF!) insulation of the internal wirings.
Page created and copyright R.Quan ©25 Oct 2015.