Reymond entered a CD4007-Based Voice Changer into the Open 7400 Logic Competition: The project uses 2 – CD4007 configured as a Gilbert Cell Double Balanced Modulator and an additional 2 – CD4007 for use as a difference amplifier. This kind of effect is known as a Ring Modulator in the audio community… Via the contact […]
Category Archives: 7400 contest
7400 competition entry: Capacitance meter
Alvaro built a Capacitance meter out of logic chips for the Open 7400 Logic Competition. His project measures capacitance of a capacitor and displays it on a 7-segment display. It works by using the said capacitor in a RC oscillator, which changes its output frequency proportionally to the capacitance in it’s RC circuit. The frequency […]
7400 competition entry: Peltier temperature controller
Michael entered a TEC temperature controller into the Open 7400 Logic Competition. Logic chips control the temperature of a thermoelectric Peltier element (TEC) heating/cooling plate. Current temperature is measured via a sensor placed directly on the Peltier. The target temperature is set by an 8bit dip-switch. The circuit will cool or heat the Peltier until […]
7400 competition entry: LED clock
Michael built an LED clock for the Open 7400 Logic Competition. He added 60 LEDs to an analog clock which are controlled by discrete logic chips. This project uses a standard analog quartz clock and adds 60 LEDs clockwise around it to display the seconds. There are 2 selectable modes via 2 jumpers: Mode 1: […]
7400 competition entry: AM radio transmitter
Andrew entered an AM radio transmitter into the Open 7400 Logic Competition: My 7400 contest entry is an AM Radio Transmitter, which nicely complements another entry. The TX frequency is digitally tunable from 520kHz – 1.6MHz, although this part of the circuit is open loop, so tuning to a specific frequency may require a slight […]
7400 competition entry: Beeping down counter
Chris decided to enter another project into the Open 7400 Logic Competition. The beeping down counter, as it’s name suggests, is a pre-settable timer which beeps and uses a display to show the seconds left on the timer. The goal of this project is to duplicate the down counting circuit used by the character Ivan […]
7400 competition entry: FM modulation and demodulation system
Alifred and his friend entered a FM modulation, demodulation and transmission system into the Open 7400 Logic Competition. An input waveform enters the Voltage Controlled Oscillator (VCO), resulting in a FM modulated waveform. This is then sent to an IR LED (through a buffering MOSFET) and is received by a photo-transistor at the other end. […]
7400 competition entry: Discrete logic amplifier
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 […]
7400 competition entry: Digital die (74XX Family)
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 […]
7400 competition entry: TTL based range finder
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 […]
7400 competition entry: TimeBonder 275
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 […]
7400 competition entry: AM radio
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 […]
7400 competition entry: Discrete logic preamp
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 […]
7400 Competition deadline has passed
The Open 7400 Competition deadline (October 21, 6am GMT) has passed. Today we will dedicate the blog to the numerous last minute entries. Normal posting will resume tomorrow. On behalf of the 7400 Competition sponsors, and the Dangerous Prototypes crew, we thank you for taking the time to enter the competition. Sponsors of the Open […]
7400 competition entry: Police lights and siren for a toy car
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 […]
7400 competition entry: Safer alarm
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.
7400 competition entry: 74Clock
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.
7400 competition entry: Charge pump voltage inverter
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.
7400 competition entry: 7400 Logic E-reader
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, […]
New 7400 Competition sponsor: Farnell
Farnell is a last minute sponsor of the Open 7400 Logic Competition. They’re donated the flux syringe and springy metal soldering iron cleaner thing we reviewed here on the blog. Get your entry in soon and this and other cool hardware can be yours.