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 to work) 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!
The 1802 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 and options!
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!
By itself, the Z80 Membership Card is a stand-alone computer to "power up" your projects, like the Arduinos or Parallax BASIC Stamps. Both Monitor and BASIC communicate via the serial port. It also has a full expansion bus to add memory and I/O cards ("shields") 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 and options!
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 RCA VIP was designed by Joe Weisbecker as an elegantly simple home computer that was easy to learn and fun to use. Announced in 1977, it had an RCA 1802 microprocessor, 2K (or optionally 4K) of RAM, a monitor program in ROM, a 16-key hex keypad, a 64x128 pixel graphics video display, and a serial port to load/save its programs on cassette tapes. That's an original VIP on top of the monitor in the photo.
For the 40th anniversary of the VIP, we made a new version you can build yourself. That's it at the bottom of the photo, hiding under its tiny keyboard! The battery box is at the right, with four AA cells to power it. Our version has the same 1802 microprocessor, but with significant upgrades in speed, memory, and features:
The computer is based on the COSMAC Elf and 1802 Membership Card, so the same software works with little or no change. For example, our first program was the 1802 Membership Card's serial Monitor ROM. The current kit comes with the MCSMP20 Monitor, RCA BASIC3, and CHIP8 programming language, using the VIP2K's keyboard and video, and serial port for load/save.
The manual is pretty basic, but should be enough if you're a skilled kit builder. Bare boards are available, and the parts are all generic and easy to get (no rare, expensive, or custom parts); but you'll need to be able to program your own EPROMs. Or order a kit, which comes with everything, including EPROMs programmed with the latest software. Click here for more information!
This little project is an 1802 Name Tag. It shows just how much you can do with an 1802 and an absolute minimum of resources! It's the size of a credit card, and runs on just 10ma from three AAA cells (4.5v). That's low enough to run for days.The 1802 scans a multiplexed 8-digit 7-segment LED display to produce four 8-character message "frames", displaying them sequentially about one every second. Every segment in each message is programmable, so it can spell out text as well as numbers.
In classic vintage fashion, messages are loaded with a 'front panel'. Since this is an 1802 computer, the front panel is nothing but switches and an LED.
The circuit has only an 1802, a 74HC241 octal buffer, and a 74HC138 1-of-8 decoder. Astute observers will note that there is no RAM or ROM! Yet it is running a program, and scanning the display.
This is a great "quickie" project! If you like puzzles, or enjoy trying to figure out how such a "mad" circuit works, click here for more information!
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!"
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). Here is the manual that comes with the kit.
The photo shows a personalized greeting that I wrote 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. Satisfaction guaranteed or your money back!
Electronikit Projects © 2006-2019 by Lee A. Hart. Created 11/5/2013. Last update 6/18/2019.
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