Electronics

Energy Meter Hacking

| steelcityelectronics

Following on from the recent teardown of a cheap energy meter, I thought there might be some potential to hack this device. Well the EOUT “pulse output” pin shows some promise. The chip’s datasheet says that the EOUT pin outputs a pulse for each unit of energy the meter measures. Additionally, this function is enabled by default.

Since this is enabled, by default, I made some mods to the case and soldered 3x wires directly to the chip.

Wires soldered directly to chip pin 21 (EOUT) and power supply (decoupling capacitor)
2mm hole in the case
PCB reassembled in case

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TO220 Single and Dual Gauge Packages

| steelcityelectronics

A friend of mine recently asked me if I knew that there are two package types for humble TO220 devices. I didn’t understand what he meant. He then asked if I had heard of single gauge and dual gauge TO220 packages. Nope still no idea. Finally, he asked if I had seen TO220 voltage regulators such as a 78L05 device with a thin heatsink?

Yes, I had seen these before, in fact I have a couple. I hadn’t really paid a lot of attention to the first time I had seen one of these components with a thin heatsink. I thought that it was perhaps a counterfeit device. That is not the case (excuse the pun). A thinner heatsink is a type of TO220 package.

Below are two TO220 devices, a 7812 12V regulator manufactured by On Semiconductor and a TIP31 NPN transistor from ST Microelectronics. A quick glance and their shape is instantly recognisable.

TO220 devices
TO220 packages for a 7812 12V regulator and a TIP31 NPN transistor.

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MJE3055 Power Transistor Teardown

| steelcityelectronics

Whats inside a power transistor? Well some semiconductor to be a transistor of course. How large would you expect the transistor’s die to be?

My guess is, that for a device that can conduct up to 10 A, the die would occupy the bulk of the transistor’s package. What’s your guess?

MJE3055 NPN transistor
An MJE3055 NPN transistor ready to be dismembered.

Lets find out with a teardown of sorts with the following MJE3055 NPN power transistor that comes in a TO-220 package.

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Skillet Reflow 0603 SMD Capacitors = Tombstones

| steelcityelectronics

A recent project involved using an electric skillet to reflow solder some APA102C RGB LEDs to a PCB. The aim was to make a device similar to the Adafruit Neopixel Strips, but arranged in a 3×3 square and using the APA102C LEDs.

Honestly, each board that was made was a fail. Electrically, they all worked correctly. The failure was during the manufacturing stage – reflow soldering very small SMD components.

Just as an aside, Adafruit Neopixel devices use WS2812B LEDs which have some very strict timing requirements – this can be problematic for some devices that use software interrupts. Whereas, the APA102C LED is a chip that does not suffer from strict timing.

Each small PCB, contains 9x APA102C SMD LEDs and 8x 0.1uF 0603 ceramic capacitors for power supply decoupling. Each APA102C LED is the large white square with white circle. Between the rows of the APA102C LEDs are the SMD pads for the 0603 size capacitors.

PCB layout for APA102C LEDs
Top surface of the PCB layout.

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