CuVoodoo #031 – controller impersonation

identifying STM32F103C clones:
The STM32F103C micro-controller has become so popular that you can find plenty of pin and code compatible clones. The issue is when they pretend to be genuine STM32. We will see how to identify counterfeit STM32F103C, using the top marking, decapsulating the silicon die, but also from inside with a firmware which will check the value and behavior of some registers.

source files watch on other devices (youtube)

Published: 2021-02-27 by King Kévin

CuVoodoo #030 – audio is killing the music

building a sound level enforcer:
for a private club I built a sound level enforcer. if the DJ is playing music too loud, the device will shut off the audio output. for that I reversed a GM1351 sound level meter to extract the measurements from the LCD interface, send them over Bluetooth to the enforcer, which will cut the power to the main audio amplifier if a set threshold is exceeded for a couple a seconds.

source files source files watch on other devices (youtube)

Published: 2021-01-28 by King Kévin

CuVoodoo #028 – every electron counts

reversing USB meter protocols for long term low DC power logging:
To figure out the energy budget provided by a solar panel for a weather station, I needed a device capable of measuring low DC voltages and currents over a long period of time. For that I used the USB Power Meter (UPM) Web-U2, but I first had to reverse engineered the BLE and USB communication protocols it provided.

documentation source files watch on other devices (youtube)

Published: 2020-09-17 by King Kévin

CuVoodoo #027 – do you prefer your meat grilled or poisoned?

building a defusing game:
For the bachelor party of a friend, I created a defusing game. Using the knowledge about his future wife, he was able to cut the right wires and disarm the bomb. This then turned on a torch which grilled a piece of meat, instead of injecting poison into it. We will learn how to drive DC and stepper motors.

documentation watch on other devices (youtube)

Published: 2020-08-17 by King Kévin

CuVoodoo #026 – dying light

building a remotely controlled flashlight:
For another attraction held during a Halloween party already mentioned in episode #025, I also built a flashlight which can be remotely controlled. This is ideal to put the participants in complete darkness and have glowing clowns chase them. For this I added a tiny micro-controller and IR receiver in off-the-selves flashlights, and used a camera shutter remote control. We will see how to deal with the size constraints using parametric search.

documentation watch on other devices (youtube)

For more details about the Halloween party and infra-red theory, watch episode #025.

Published: 2020-07-26 by King Kévin

CuVoodoo #025 – live scare jump

building a remote controlled strobe light:
For an attraction held during a Halloween party, I built a device which allows to send strobes of light. Combined with a ghost apparition, this was the ideal setup for a scare jump. The strobe controller uses an LED flood light, a solid state relay, and an infrared remote control. We will see what mechanical and solid state relays are, how to operate them, how infrared remote controls work, and how receive decode their signal.

documentation source files watch on other devices (youtube)

The Halloween party is called Balloween. It take place in Paris, and is mainly French. An entrance fee is required, but it barely covers the cost of the consumables. I and all the staff helped in our free time and at our own expenses, but it is a lot of fun and nothing beats scaring innocent victims ;).

P.S.: To create light strobes a stroboscope might be the more appropriate, but I did not have one at the time I built this device. I am also not sure how I would control the couple of kV required to fire the flash tube. Flood lights are more ubiquitous, and can also be switched on continuously.

Published: 2019-08-17 by King Kévin

CuVoodoo #024 – reviving lost memories

building a spot welder to replace batteries in Game Boy cartridges:
Game Boy game cartridges require energy from an internal battery to keep the save state. When this battery is depleted you can replace it using a coin cell and some copper tape. For better connections through metal tabs I also built a small spot welder using a super capacitor.

watch on other devices (youtube)

I got all parts from AliExpress (100F super capacitor, LM2596 battery charger, nickel strip).

Spot welders can also be built using a car battery and relay solenoid/starter, or a micro-wave transformer and solid state relay. This solution is larger and costs a bit more, but allows controlling the weld duration for repeatable results (instead of requiring experience).

For even more professional spot welding (with energy control), have a look at the kWeld or Arduino Spot Welder (sources).
Published: 2018-08-22 by King Kévin

CuVoodoo #023 – forever olaf

building a power outage alert notification:
We will build a device to notify us in case of a power outage in our home. For that we just need to re-purpose a GSM tracker.

documentation watch on other devices (youtube)

Post-scriptum: do not waste any time on the Orange Pi 2G IoT.
While the idea and the hardware sound nice, after working a bit with it, there are just too many issues:

  • the official Linux distributions are old (> 1 year), the kernel is even older (it still is a 3.10)
  • the serial port is unstable (freeze on overrun)
  • the wifi is very unstable
  • the wifi MAC changes at every boot
  • the battery managment actually does not work at at all (no power and no charging due to a mistake in the design)
  • it is not supported by armbian

Published: 2018-05-27 by King Kévin

CuVoodoo #022 – amanuensis slavery

reversing a printer cartridge chip:
How does a printer know when the cartridge is empty? Instead of using a sensor, the toner or ink level information is simply stored in memory and updated after each print. This technique also applies to my old laser-jet printer. I was able to identify the chip on the toner cartridge as a 1-Wire EEPROM with some authentication features. We will see how and what the 1-Wire protocol is. I also re-implemented this chip and was able to pass authentication thanks to a secret key I dumped from another chip, allowing me to fool the printer in thinking the toner cartridge is never empty.

documentation source files watch on other devices (youtube)

Published: 2017-09-15 by King Kévin