Dangerous Prototypes

Dmitriy entered his lighting effects generator into the Open 7400 Competition.

The basis of the device is a multi-bit digital sequence generator that is implemented on a serial shift register [1]. The repetition period of the sequence is determined by the number of bit of a register and much higher than the repetition period clock. For a sequence containing all possible states of the register, excepting the zero state (so-called M-sequence) the value of the period is Tn = (2n-1) / f, where n – number of bit of a register, f – clock frequency in Hz.Via the contact form.

Via the forum.

T0mpr1c3’s open 7400 Logic Competition entry is the Doctored calculator animated name plate:

Here is another single chip dead bug offering. The circuit has been out there for at least a decade.

Check out the video after the break. Continue reading “7400 competition entry: Animated LCD name tag”

Nick’s Open 7400 competition entry is an FPGA that is implemented in 7400 series discrete logic ICs:

Building a microcontroller or CPU out of discrete logic is a popular hobbyist pursuit, and it serves a useful purpose. Building a CPU from scratch teaches you a lot about CPU architecture and tradeoffs; it’s an interesting and instructive exercise. So, I wondered, wouldn’t building an FPGA out of discrete logic be similarly educational? Hence, my competition entry: an FPGA (or rather, a ‘slice’ of one) built entirely out of discrete logic chips.

Check out the video after the break. Continue reading “7400 competition entry: Build your own FPGA”

This I2S DAC with a Class D amplifier output has been entered into the open 7400 competition. It uses a mix of 74HCxx and 4000 CMOS series logic ICs to achieve the desired result.

My last minute entry to the 7400 series logic competition. I’m using a SN74HC132 hex NAND gate, a CD4094BE 8 bit shift register, two CD4585BE 4 bit comparators, a SN74HC590 8 bit counter, and a SN74HCU04 hex inverter. The i2s data and clocks are used to generate a PWM signal by comparing the data with counter values. The output from the comparators is used to drive a class D amp.

This ended up being more of a proof of concept, as I ran out of time to debug everything. There are some bugs that need to be worked out, but I didn’t have any logic analyzer to debug the 8 bit bus. However, the frequency sweep shows everything working for the most part!

Check out the video after the break.

Via the contact form.

Continue reading “7400 competition entry: I2S DAC with a Class D amplifier output”

Check out Matthew’s 7400 contest entry, a 74xx based signal strobe for emergencies, as well as search and rescue situations.

This a signaling strobe, an enhanced one with a siren. My device is built off of 7400 NAND Quad Gate, 2x 7476 J/K Flip Flop, 7432 OR Quad Gate and 4x 555 Timers. Now of course, there are a few passive components like capacitors, resistor, 5 volt regulator, LEDS, and several switches. All built on one large breadboard, but I believe this could be fabricated on a 2×4 PCB, maybe smaller

To be able to complete the project for the 7400 competition, I wasn’t able to find locally the I/R diodes or the high output LEDs that will be mentioned later. I will go over it POU, point of use, and a bill of material will be included at the very bottom.

Via the contact form.

Want to test your power supplies? How about using a constant load with a Nixie display, built entirely out of 4000 series CMOS logic chips.

This is a Constant Load generator that is controlled by a keypad. When I started this project I was not sure what it would end up being so I built in in modules that are interconnected. This gives me greater flexibility and it is easier for a beginner to understand the schematics and operation of the parts.

I use only CMOS 4xxx -logic running on 12 volts with the exception of the Russian K155N1 Nixie drivers – they are TTL and uses 5 volts.

Check out the video after the break. Continue reading “7400 competition entry: Constant load with nixie readouts”

Do you need an incubator for hatching eggs?  T0mpr1c3 shows you how to easily make a homemade egg incubator:

This is a project from a couple years ago, which I published on the members’ pages at the Backyard Chickens forum: An automatic egg incubator with PID temperature control and periodic egg-roller, built into a microwave oven. The rotary egg turner employed the microwave turntable and a stationary lattice containing the eggs. A timer circuit comprising a 74HC4060 counter and CD4013 dual flip flop set the turntable in motion several times a day, rolling the eggs.

Check out the video after the break.

Continue reading “7400 competition entry: Periodic egg turner for incubator”

Check out Jussi’s 7400 contest entry, the polonaise machine. It’s a sound generator with the Telemann’s Polonaise tune incorporated into the design.

After about half an hour of brainstorming I came up with the idea of a modern musical box. In a few moments I had the core of the machine ready on a paper and I found a suitable tune; Telemann’s Polonaise. It’s simple, short and has only nine different notes.

Class D amplifier using digital logic is the open 7400 competition entry by hasn0life:

The entry is a class D amplifier made entirely out of discrete digital logic components. I took great pains not to use op amps or transistors or any active devices besides logic gates. Though the amplifier outputs square waves, the process to generate them is entirely analog. As such, this design is an example of using digital gates in an analog way.

Check out the video after the break. Continue reading “7400 competition entry: Class D amplifier using digital logic”

It’s time to Press Your Luck! Check out Christopher’s nixie-based Press Your Luck game for the Open 7400 Logic Competition :

Press Your Luck (tv game show) in Nixie form, getting a W (view the tube upsidedown) is like getting a Whammy. See how many points (other cathodes) you can get before hitting 3 whammies.
People on the show would always say “NOWHAMMY NOWHAMMY NOWHAMMY STOPPP!!!”

Build something that uses or abuses a logic chip and get amazing boards, tools, and other swag. The Open 7400 Logic Competition promotes awareness of the basic building blocks of modern circuits. Devious geeks ignited the computer revolution with discrete logic computers, what can you do? Details and entry form here.