Gas or Beer contraption

ElectroniKits (tm)

Clever, creative, and fun electronic projects
by Lee A. Hart

The 1802 "Membership Card" Microcomputer

Once upon a time, microcomputers were simple and easy to understand. So simple in fact that a kid like me, with no computer experience whatsoever, could actually understand them, build them, program them, and put them to work in his very own projects! The first microcomputer that I built (and actually got working) was the COSMAC 'ELF', featured in the August 1976 issue of Popular Electronics magazine. It used the RCA 1802; an exceptionally easy to use microprocessor. The ELF taught me about computing, and got me started on a career in engineering.

Today's computers are far more powerful than the 1802. But they have also become so complicated that virtually no one can build them or truly understand how they work. I decided to do something about it. The Membership Card is a reproduction of the original Popular Electronics Elf computer, repackaged to fit in a pocket-sized Altoids(R) tin. It uses no custom parts, no surface mount, and there is no need for PCs, megabyte compilers, or secret software to use it. Now you can learn about computers right from the ground up, and really understand how they work!

FeaturesMembership Card in Altoid tin

Membership Card Kit


The Membership Card is available in kit form, bare boards, or just download the manual and build it yourself from scratch. Click here for more information, pricing, or to purchase.

The Z80 "Membership Card" Microcomputer

Now there's a Z80 version of the Membership Card! Introduced in 1976, the Z80 became one of the most popular microprocessors of all time. It quickly replaced the Intel 8080, and was used in many classic microcomputers like the Osborne O1, Kaypro 4, Radio Shack TRS-80, Heathkit H89, and more. And it's still in production today, in the "secret heart" of products where modern micros would simply be vast overkill (for example, the Texas Instruments TI-84 calculator).

The Z80 Membership Card is a complete computer that fits in an Altoids tin. Inspired by the Heathkit H8 computer, it is thoroughly documented and easy to build, with big parts, big pads, and big traces and spaces. It uses only classic generic parts common in the 1980s -- no custom parts, and no surface mount. BASIC is included in ROM, so it's completely self-contained: You don't need a PC, Windows, megabyte compilers, or secret software to use it. Now you can learn about computers right from the ground up, and really understand how they work!

Z80 Membership Card



Z80 Membership Card Front Panel

By itself, the Z80 Membership Card is a stand-alone computer that can "power up" your projects, like the Parallax BASIC Stamps or Arduino microcomputers. Both the monitor and BASIC can be run via the serial port. It also has a full expansion bus to add memory and input/output cards ("shield") to put it to work.

The Z80 Front Panel Card plugs onto the Z80 Membership Card to add a hex keypad, 7-digit hex display, piezo beeper, timer, and TTL/RS-232 serial I/O port. The Z80MC program in EPROM uses the front panel to provide a sophisticated machine-level monitor. Even without connecting to a PC or other computer, you can:

A unique feature of the ZMC monitor is that it remains active even while your program is running. It can continuously display the contents of a register, I/O port, or memory location, so you can see when your program is modifying it.

The serial port sends and receives data at 9600 baud. Plug it into a terminal, or PC running a terminal emulation program like Hyperterm. With this, you can type the Z80MC monitor commands on the PC keyboard, and see the results on the PC's screen. You can also upload and download data and programs as simple ASCII text, or Intel HEX files, or XMODEM formats.

The Z80-SIO card adds up to 512k of bank-switched RAM, a second UART serial port, and a Compact Flash card to provide "disk" storage. With this card, the Membership Card runs the CP/M-80 operating system.

Bare boards are available to build it from scratch with your own parts. The entertaining "retro" manual has detailed assembly instructions, schematics, parts lists and sources. Click here for more information, prices, or to purchase.

The Face Card

If you've never built anything with a microcomputer, here's your chance. This project will show you just how simple a microcomputer can get. It may also be the silliest use for a microcomputer yet! The photo shows it with a holiday hat sitting under the Christmas tree.

I designed this back in 1978 to randomly blink a set of LEDs with the classic RCA 1802 microprocessor. I realized I could arrange the LEDs to form a face. The eyes roll left and right, and blink. The eyebrows raise and lower, and the mouth smiles, frowns, opens, and closes.

How does it work? The LEDs are connected to the microprocessor's address, read/write, and state code lines. The program... well, there is no program! The 1802 has no internal memory (no RAM and no ROM). The data bus is left floating, so it fetches random values, and executes them as if they are a "program". One of the data lines is pulled high; this prevents the data bus from ever being 00, which is the HALT instruction.

The 1802 is being clocked at 1 Hz, so the expressions slowly change. Note that this is not MHz or GHz; 1 Hz is one cycle per second! Let's see you find another microcomputer application that runs this slowly.

The Face Card is available as a complete kit, a bare board, or click here to download the manual in PDF format, complete with schematics and parts list. The kit comes with the 36 red, yellow, and green LEDs, the 1802 microprocessor, and everything else that goes on the board. All parts are thru-hole (no surface mount), and all pads and spacings are large and well spaced for easy soldering. Add a 4-6 volt power source (four AAA batteries, for example), and you're finished!

The board measures 3.5" by 2" (9mm x 5.4mm) and fits perfectly in an Altoids candy tin, with room for a 4-cell AAA battery holder for power. Use a pushbutton switch to turn it on when you open the lid, and surprise your friends when they reach for a mint. :-)

The Face Card

Face Card bare board -- $9.95. Includes the bare PC board, parts list, and instructions. Shipping and handling; $3 in the USA, $10 international.

Face Card kit -- $19.95. Includes the PC board, 1802 with all parts, and instructions. Shipping and handling; $5 in the USA, $15 international.

Assembled Electronic Christmas Tree

An Electronic "Christmas Card"

Looking for a great Christmas "card" to highlight your electronics skill? Need the perfect gift for that electronics hobbyist or budding engineer? How about this electronic Christmas tree kit?

It's a 6" high tree, decorated with colorful blinking lights. It's the perfect beginner's kit, with large parts, big pads, and wide traces for easy soldering (no tiny surface mount parts). The circuit board, detailed instructions, and all parts except battery are included. It runs on a standard 9 volt battery, which doubles as a stand. The clever micropower CMOS circuit operates for weeks. It even works with batteries too dead for anything else (so put your old smoke detector batteries back to work). Best of all, experience the joy of saying, "I made it myself!"

Electronic Christmas Tree Kit

This is the original blinkie-LED Christmas Tree! I've been making them for 30 years now as a special gift for family and friends. I wrote an article on it for Modern Electronics magazine in 1988. It's been widely copied (but never equalled) ever since.

The photo shows a personalized greeting that I write on my own trees. If you specify a custom greeting, I'll add it at no extra charge. Otherwise, I send it blank so you can add your own greeting.

Tools needed: Wire cutters, a small screwdriver, solder, and a soldering iron or gun. US orders will be shipped by US First Class Priority Mail. For international orders, ask about shipping costs. Satisfaction guaranteed or your money back!

Christmas Tree kit -- $7.95. Includes PC board, with all parts and instructions. Shipping and handling; $3 in the USA, $10 international.

Electronikit Projects © 2006-2018 by Lee A. Hart. Created 11/10/2013. Last update 1/23/2018.
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