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.
replacing the sensor of a dehumidifier:
the humidity sensor modules of a dehumidifier kept failing, and no replacement is easily available anymore.
after reversing its communication protocol, I was able to create my own module.
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.
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.
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.
For more details about the Halloween party and infra-red theory, watch episode #025.
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.
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.
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.
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
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.
building a digital clapperboard:
Clapperboards are often used to synchronize audio and video recordings. I'm also using such a tool for the podcast, so I decided to make my own digital version of it. After all I only have to show the scene, take, video and audio recording numbers. This can easily be done using electronics instead of having to write everything down myself.
For that I used a DS1307-based RTC module using the I²C protocol, seven TM1637-based 7-segment 4-digit displays using an I²C incompatible protocol, two MAX7219-based 7-segment 8-digit displays using a SPI compatible protocol, a piezoelectric element, and a custom power control circuit. We will also see how these communication protocol work.