The Open 7400 Competition is over and the winner is…. Capacitive Sensing, the Hard Way! This is a project that is somewhat simple when done with a microcontroller but takes quite a bit of effort to pull off with 7400 chips. I think the winners are still trying to determine who wants what since I haven’t heard who is going to be awarded the three IR Jammer kits yet.
“The capacitive inputs are selected using 74xx-ized analog switches (‘4051). The channels are selected using a synchronous ‘161 counter to feed a RC-oscillator build around a couple of ‘132 Schmitt-trigger nand-gates. The channel counter can be put on hold using the DTR signal from the RS232 port. The counter is automatically advanced by the channel sequencer (if DTR enabled) after the measurement period. There is of course a 16-to-1 analog multiplexer available, but it comes in a 24-pin package and that is monster size compared to the 16-pin package of the ‘4051. Besides, we need at least one inverting Schmitt-trigger gate and the options are 6- or 4-in-a-package. No reason to let the gates go unused. The design, as is, uses one extra analog switch package, but still saves space on the board.”
There sure was a great number of entries to the contest, you can browse through the list of all the entries below.
- Nixie tube clock
- Moving dot running light
- Propeddle software defined 6502 computer
- 2 bits divider/multiplier
- Telephone Intercom from TTL
- Pen holder
- Water level indicator
- 74LS00 based full wave rectifier
- Lazarus-64
- PCPU, homebrew minicomputer
- Capacitive Sensing, the Hard Way
- Sychnometro Hz
- Pure TTL clock
- New earth time (NET) digital clock
- Discrete servo driver
- Discrete logic POV clock
- Money counter
- Masochist’s video card
- Animated LED Christmas sign
- Analog comparator
- SPI LCD backpack
- Hex KeyPad
- TTL Tilt Sensor
- Lights out game
- TV pattern generator
- Four digit RPN calculator
- CMOS digital clock
- 7400-based USB prank
- The Computer
- Illogical Dickson Doubler
- 7400 Logic E-reader
- Charge pump voltage inverter
- 74Clock
- Safer alarm
- Police lights and siren for a toy car
- Discrete logic preamp
- AM radio
- TimeBonder 275
- TTL based range finder
- Digital die (74XX Family)
- Discrete logic amplifier
- FM modulation and demodulation system
- Beeping down counter
- AM radio transmitter
- LED clock
- Peltier temperature controller
- Capacitance meter
- CD4007-based voice changer
- Accelerometer controlled racing game
- Drum machine
- Etch-a-Sketch toy
- Game of Life with CMOS logic
- Heat generator
- Wheely bin night reminder
- Horologium Romanum
- 8-Channel, 6 -MSPS USB logic analyzer
- Discrete Logic Drum machine
- C-IR capture device
- Flickering Jack-o’-lantern
- Homemade 7400
- Ternary base-3 electronics using 74HC4052
- 80M direct conversion receiver
- Logic PLL based switch-mode power supply
- Silly bunch of unbounced switches
- Bad driver feedback 40×16 LED display
- Nixie tube PLL synthesizer for retro style radio
- RTC with gate IC