Haley0918 added another entry to the Open 7400 Logic competition: Discrete logic amplifier: This is my second entry for the 7400 logic competition. It’s a discrete logic amplifier made of mostly discrete logic chips. This amplifier is a continuation of my previous discrete logic preamp. The main objective here is to amplify the input signal […]
Sean Breen entered his Digital die (74XX Family) into the Open 7400 Logic Competition: Here is a rather simple but practical use for digital electronics…..dice! (or in the case a single die) Unlike many of the kits found online this one does not use a micro controller. The entire circuit is based around 74LSxx logic […]
Udif entered the TTL based range finder into the Open 7400 Logic Competition. It uses an ultrasonic sensor to determine the distance to an object. The sensor outputs a pulse, the width of the pulse is proportionate to the distance measured. The sensor signal drives a clock which in return increments a counter. The clock […]
Sigitronic built the TimeBonder 275 and entered it into the Open 7400 Logic Competition. It is a versatile timer that uses the mains frequency as the clock signal, both 50Hz and 60Hz are supported. It can time events ranging from 100ms to 99.9s with a resolution of 100ms, or up to 999s with a resolution […]
Jason entered his AM radio into the Open 7400 Logic Competition: One unusual use for a logic chip is as an analog amplifier. Most logic with inverting outputs can be used this way. In order to demonstrate this functionality, I’ve built an AM radio with a 74HCU04 inverter. The inverters are used both as RF […]
Haley0918 entered his Discrete logic preamplifier into the Open 7400 Logic Competition. Through some experimentation he figured out that a XOR gate shows some analog properties. By modulating the input between 0.8v and 1.2v the output was swinging between 1v-4v, making the logic IC a preamplifier with a gain of 7.5. You can check out […]
Nathan entered his Police lights and siren for toy car into the Open 7400 Logic Competition: A Little Tikes Patrol Police Car was retrofitted with a battery-powered emergency police lights and siren system as an entry to the Dangerous Prototypes Open 7400 Logic Competition. The circuit design focuses on simplicity and efficiency of part utilization […]
Spanner888 entered his Safer Alarm into the Open 7400 Logic Competition: This system provides a simple, effective and practical enhancement to existing alarm systems to tell you if your alarm has been triggered, tampered with, or lost power. Via the contact form.
Arthur entered his 74Clock into the Open 7400 Logic Competition. I uses a large 7 segment display and has a battery in case of power outage. A clock is a useful thing, so let’s build one. Via the contact form.
Daniel built a charge pump voltage inverter for the Open 7400 Logic competition. It uses the 74LV14 Schmitt trigger to provide a clocked signal, which is then connected to the inverted charge pump circuit to provide a -5V supply. Via the contact form.
Snorre built a Logic E-reader for the Open 7400 Logic Competition. It is a e-reader build completely from logic chips and 2 eproms. The e-books are displayed on a old analog oscilloscope. The front page says EEPROM instead of EPROM. I don’t have access to a burner right now, so i can’t fix it (ironically, […]
Jonathan entered his illogical Dickson doubler into the Open 7400 Logic Competition. My entry demonstrates how you can use the internal protection diodes and back powering to power a 74HC14 at a voltage “double” (minus diode drops) that of the primary power supply. This method was tested on a 74HC14 and a 74HC595, but it […]
John’s second entry into the Open 7400 Logic competition is a working computer with serial I/O and a lights ‘n switches front panel. He built a 8bit CPU with a single accumulator, basic arithmetic (+,-,&,~,<<,>>), conditional branching and subroutines, as well as 1KB of RAM. After building and testing that it works, he unfortunately had […]
Arup entered his USB device not recognized design into the Open 7400 Logic Competition. It uses a logic chip to stimulate a USB host just enough to get a “Device not recognized” response from Windows. Once the prank succeeds a “1” is displayed on a 7 segment display. Via the forum.
Giuseppe built his CMOS digital clock two years ago and decided to enter it into the Open 7400 Logic Competition. By using a 2Mhz quartz crystal and a 21bit counter he managed to make a 1Hz clock signal which drives his design. Implementing 2 binary counters programed to count to 60 he managed to get […]
John entered his four digit RPN calculator into the Open 7400 Logic Competition. This is the fist of two entries he made while attending “Digital Hardware Lab” courses at the University of Utah. It is a 4 digit RPN calculator that can add and subtract, designed entirely out of logic ICs. The first few weeks […]
Ajoy built a TV pattern generator for the Open 7400 Logic competition. Using 74C14 Shmitt inverters to generate various timing signals, he later combines them using a few NAND 74C00 gates to get a B&W TV video signal generator by CCIR-B standards. A full write up explaining the operation of his circuit, along with the […]
Bertho entered his Lights out game into the Open 7400 Logic Competition. After working out the math behind lights out, Bertho decided to make his own using only logic chips. The object of the game is to turn the lights off by using a + shaped mask.The board automatically generates random patterns over a 5×5 […]
Chris added another entry to the Open 7400 Logic competition: TTL Tilt Sensor. His device works by converting accelerometer analog outputs into digital signals via 3×4 comparators, 6 are used for the X-axis and 6 for the Y-axis. From then on discrete logic chips are used to convert the different signals into various positions on […]
Joseph built an analog comparator for the Open 7400 Logic competition. Using two NAND 3-input gates and a D-type flip-flop, he build a clocked analog comparator. After reviewing the internal composition of a CMOS NAND 3 gate he noticed that two of them connected in the right way make up a comparator. To make his own version he used a D-type flip-flop to […]