Dangerous Prototypes

Here’s a 6 digit frequency counter by Yi, entered into the Open 7400 Competition.

During the Winter break my dentist convinced me that I needed to have my 2nd wisdom teeth removed. Having done this previously without much pain, I thought it would be a good idea. It turned out to be much more involved and I was out of commission for 2 weeks which was no fun at all. I was in bed most of the time, but one day I made myself get out of the house to buy the temperature controlled soldering iron that I’ve always wanted. I needed an excuse to use the soldering iron so I figured that I might as well as make a frequency counter which is something that I’ve always wanted, but lacked in my lab.

Nakul Rao I, Nischal Rao, Nikilesh, and Sandesh VS entered a bicycle exercise meter and burger alarm into the Open 7400 Competition. Their project keeps track of your bicycle’s speed, cadence, and distance while you’re exercising. It also acts as a burglar alarm when you’re away.

This is something we had done about an year back. We felt it would be nice to enter this into the competition as we have based the entire project on 40xx logic chips.
Project Members: Nakul Rao I, Nischal Rao, Nikilesh, Sandesh VS

Via the forum.

Don’t wanna lose your car? Build a CMOS 4000 series car alarm and enter it in the open 7400 competition.

Built way back in the 1980s this CMOS Car Alarm provided an entry & exit alarm for my wonderful little Mini. It was built from CMOS series logic to reduce the current consumption and the circuit only drew 20mA with both LEDs lit! I particularly like the oscillator design and the fact you don’t need any current limiting on the LEDs as the CMOS logic self-limits. Enjoy!

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.

Here’s an interesting way of designing analog devices using digital chips. This sine wave generator s based around mosfets contained in the CD4007 IC (a dual complementary pair of mosfets and an inverter).

The CD4007 dual complementary pair and inverter is primarily intended for digital logic circuits. It contains an inverter, and two pair of PMOS and NMOS transistors that can be configured to implement any CMOS logic gates. Since we now have access to pairs of transistors, it should be okay to use these transistors for other purposes than digital, in other words: analog. This idea is not new, in fact this article has already mentioned this possibilty, and now I would like to take the challenge to build something somewhat useful out of it, as simple as possible…

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.

Via the contact form.

Jvok’s open 7400 Logic Competition entry is the CD4000 digital alarm clock. As the name suggests this is an alarm clock based on CMOS 4000 series logic ICs.

I designed this clock over the course of two weeks for the Open 7400 Competition. The clock, which is made from 25 CD4000 ICs, three 555/556 ICs and a handful of discrete components, includes an alarm and a way of setting the clock that until now I have only seen implemented using microcontrollers. All this makes for a rather involved circuit, but I have split the schematic into a number of pages, which will hopefully make it easier to follow

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.

Here’s another 7400 entry, BrainF**k machine. This is a home brew 8bit CPU with 8 instructions, supporting the BrainF**k esoteric programing language.

It is possible to design a relatively powerful processor with a very small amount of logic circuitry, provided that the architecture and the instructions are carefully built for a concrete application.
74 logic circuits are still very useful today, new families with better parameters come out, old circuits are removed and new ones added.
Thanks to this project, I learned a lot about CPU design, logic circuits and logic simulation. I hope it will inspire other projects.

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.

Via the contact form.

Control your lights via a 7400 based dimmer. This is RodLophus’ entry for the open 7400 Logic Competition:

The idea is: For a typical dimmer, when you apply a pulse on the gate terminal of the TRIAC, it turns on – and stays on until the mains voltage crosses the 0V. So, varying the “firing angle” (“where” on the mains sinusoidal voltage the pulse will be applied) we can vary the amount of power that is delivered to the load. Thus, if the load is a lamp, its brightness will vary according to the TRIACs “firing angle”; the earlier we fire the TRIAC after the mains voltage crosses 0V (lower firing angle), the brighter the lamp will be.

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.

Here’s David’s 7400 entry, the Mr. @#?%!…A 74xx based Q*Bert-ese obscenity generator:

In honor of the 30th anniversary of Q*Bert’s release in arcades, I present “Mr. @#?%!”… A 74xx-based Q*Bert-ese Obscenity Generator, built exclusively using parts available in 1982.

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.

Miguel sent in his entry to the open 7400 competition. It’s a CMOS frequency counter based around the CMOS 4000 series logic chips. It’s capable of counting for 1 Hz up to 1 MHz.

The project consists of a frequency counter that uses only old-school CMOS chips: 4511 display drivers, 4029 decade counters a 4521 24-stage frequency divider and a 4011 chip with 4 NAND gates. The frequency counter counts from 1 Hz to 1 MHz (999.999 KHz)

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.

Via the forum.

Check out Alex’s useless machine with a chain switch. It’s operated with 4 servos and uses 11 7400 logic chops. It’s his entry to the Open 7400 Logic Competition:

This is a last minute (and very useless) entry. I wanted to make something that shut itself off, but I wanted it to be different than all of the other useless machines out there. I also wanted it to be fairly complicated for this contest. The result is an arcade shaped device that has one of those switches that your fan or grandmother’s lamp might have, with an arm, gripper, and two doors to conceal the arm.   There is a total of four servos controlled by eleven 74xx chips on a wire-wrap board.

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.

Oakkar7 shows you how to make an awesome DIY musical keyboard using only 7400 logic.

The idea is to design and construct an electronic musical keyboard with some functions, effects etc,. This is my old school project and I remake and modified it. It is fun.

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.

This open 7400 competition entry is a clock which displays it’s time as text on 32 5×7 dot matrix displays. The display itself is driven via a board that was scavenged from an East-German numerical control unit.

I build this clock with an old display-board from an east-german numeric control. It has a one-line display with 32 5×7-dot matrix displays (old VQC10 from the GDR). The clock shows the time as a text.
The circuit on the breadboard is made out of 14 74HCxx chips and two EPROMS.

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.

Via the forum.