Rev B 1802 "Membership Card"

Last updated July 14 2011. Edited by Herb Johnson, (c) Herb Johnson, except for content written by Lee Hart and others. Contact Herb at, an email address is on that page.

[assembled kit] Here's the assembled Rev A 1802 Membership Card, with a nickel to size it up. The Rev B kit was available September 2010 - July 2011 and looks identical to the Rev A shown here, with one chip changed. The Rev C is nearly identical to Rev B but includes a PC board to cover the Altoids box. Go to the Rev C Web page for current information. This Web page will be stablized to support Rev B board and kit owners.

The Rev B manual is this .RTF file at this link. and this .PDF file at this link. The Rev B Membership Card Product Sheet is on this Web page. Check the Membership Card home Web page for more information, links, and the current status of the kit.

Prices, ordering, contact

Refer to the Membership Card home page for the current ordering status of the Rev B and Rev C kits. An email address is there to order or contact. - Herb Johnson

[parts kit] [empty boards] On the left is my own Rev A kit parts from Oct 2010, and the unpopulated Rev B boards are shown on the right. Here's a link to the Rev B schematic as of Nov 2010.

Go to the Rev C Web page for more information on that product. This Web page covers the time period from the Rev B announcement on Aug 18 2010, to the end of the Rev B distribution in July 2011, and covers construction, fixes, etc. History and development up to the Rev A design Membership Card is on an earlier development Web page as linked. A summary of that history, and links to previous kit constuction, testing hardware and all software is on the Membership card home Web page. - Herb Johnson


Initial testing and programming
Rev B description
Engineering Data
Errors and corrections

Initial testing and programming

See this document on Testing the 1802 Membership Card with small toggle-in programs. Basic operations of the front panel are described. Use of the parallel port for programming will be described in this linked document. Other links to testing hardware and software are on the Rev A development Web page. - Herb Johnson

Rev B description

Aug 18 2010, Lee Hart: "The Rev.B version of my Membership Card is ready for delivery! For those just tuning in, the Membership Card is a reproduction of the original Popular Electronics Elf computer, but shrunk to fit in an Altoids tin! It works the same, and runs the same software." Here's a link to the Rev B schematic as of Nov 2010.

1. Membership Card:

- 1802 microprocessor (option for 1804/5/6 without load mode).
- 2k-32k memory chip socket; accepts
6116 2k RAM 6264 8k RAM 62256 32k RAM
2716 2k EPROM 2732 4k EPROM 2764 8k EPROM
27128 16k EPROM 27256 32k EPROM (or equivalents)

- supercapacitor to maintain RAM contents with power off
- one 8-bit output port (OUT4)
- one 8-bit input port (INP4)
- RC clock with pot (slow for low power, fast for high speed)
- the usual 1802 I/O bits (Q, EF1-EF4, INT, etc.)
- all I/O and power brought out to a 30-pin header
- size: 3.5" x 2.125"
- power: 3-6vdc at 1ma (plus whatever the memory chip chosen requires)

2. Membership Card Front Panel:

- plugs onto the 30-pin connector of the Membership Card
- provides the Elf front panel interface and DB-25 interface 
- 8 data output LEDs (memory reads and OUT4)
- 1 Q output LED
- 8 data input toggle switches (memory writes and INP4)
- read/write memory, run/clear, run/load toggle switches
- 1 input and EF4 pushbutton
- "stand alone" memory read, write, program load, and run operations
- no PC, external hardware, or any onboard program, are required.
- size: 3.5" x 2.125"
- power: adds about 3ma for each LED lit

DB-25 PC parallel port connector on Front Panel:
- has all I/O and control signals to classic PC parallel port 
- allow full front panel operation by a PC 
(with appropriate software; still being written).

The two boards stack, and will fit in an Altoids tin. Only common readily available parts are used (the 1802 is the hardest part to get). All thru-hole parts, for easy assembly (no surface mount).

Compared to Rev.A:

- Reduced power consumption, by only selecting memory during TPB.
- Fixed an output latch timing problem (74HC374 and a new capacitor).
- Changed IN/OUT port number from 5 to 4, to be the same as the Elf.
- Larger pads and wider spacings on the solder side, to make soldering easier.
- Numerous small "tweaks" to the layout to clean it up a bit.

Changes from Rev A to Rev B are on this linked Web page. Discussion of those changes is currently in this linked text file. - Herb Johnson


I wish to publicly thank those who purchased the rev.A Membership boards, who have been so very helping in testing and improving it. In thanks, I will send them each a *FREE* rev.B board set on request.

Work to be done: We're still working on developing and improving the Membership Card. Software to control it from a PC still needs to be done. The manual is pretty crude so far; but luckily, it works the same as the PopTronics Elf so all that's written for it applies here as well. I will supply the Altoids case with kit orders, but can't drill the front panel holes for you. And, we don't have a jazzy front panel labal yet. Maybe a design contest is in order? :-)

- Lee Hart, Aug 18 2010

Refer to the Membership Card home page for the current ordering status of the Rev B kit. An email address is there to order or contact.

Engineering Data

Lee has boards in hand as of early Sept 2010, and is packing and shipping some kit and board orders.

Sept 5 2010: Power consumption

I built my own and have done some testing. Power consumption is definitely reduced. Power consumption running a program with the pot at min/max frequencies, with a Hitachi HM62256P-12 32k byte RAM:

VCC    ICC at clock(min)    ICC at clock(max)
---    ----------------    ----------------
3v    .12ma    13.5 KHz    .39ma    280 KHz
4v    .25ma    9.24 KHz    .71ma    350 KHz
5v    .45ma    7.45 KHz    1.06ma    341 KHz

I've had it save a program for 10 minutes [powered only by the supercapacitor].

Sept 30 2010, lee hart Responding to a question, Lee said "With the rev.B board, a Hitachi HM62256 32k RAM is drawing well under under half a milliamp *running*. AA alkaline cells are good for that for about a year. The front panel draws essentially zero, if the LEDs are off and the data switches are up. Plus, I've done a little more testing, with different RAM chips and on two different boards. The above numbers are fairly representative. I'll try to tabulate the differences between RAM chips, as that is the largest variable." - Lee Hart

Zener diode D11

The part supplied is a 1N5231B 5.1v 5% 500mw zener diode. It's fine for general use, and does a good job of holding the max supply voltage under 5.5v to protect the supercap C5.

But it draws more supply current. I also got some low-power 1N4625 5.1v 250mw zeners. They draw about 1/10th the current at any given voltage. This is good for micropower applications, but a higher voltage supply can easily overwhelm its ability to keep C5 under 5.5v. Here are the supply currents of these two zeners (average of 5 parts of each):

VCC =     3v        4v     5v     5.5v    6v
-----     --        --     --     ----    --
1N5231    1.4ua    26ua    6ma    44ma    86ma
1N4625    0.35ua    8ua    .12ua  1.8ma   30ma


I've tried several different colors of LEDs. Whites cost the most, and need the most voltage to work; but are the brightest for a given current. Reds are the opposite; cheaper, lower brightness, lowest operating voltage. I'm supplying red LEDs and R11=1k with the kits. Here is the additional supply current per LED, and perceived brightnesses at different VCC voltages for the two extremes:

         R11    2v    3v    4v    5v
         ---    --    --    --    --
white   3.3k    0ma    .12ma    .38ma    .68ma
                off    dim    normal    bright
          1k    0ma    .27ma    1.1ma    2.05ma
                off    normal    bright    very bright
red     3.3k    .13ma    .43ma    .73ma    1.04ma
                very dim    dim    dim    normal
          1k    .39ma    1.35ma    2.33ma    3.31ma
                dim    normal    bright    very bright 

- Lee Hart

standby mode, nonvolitile RAM: You don't have to remove the Front Panel board to go into standby (minimal power consumption). Power connector P4 has 4 pins:

pin 1 = positive supply (3-6v)
pin 2 = Standby/Run; tie to pin 1 to run, leave it open for standby
pin 3 = LEDs; tie to pin 4 to enable LEDs, leave it open to disable
pin 4 = negative supply (3-6v)

So, for minimum standby power, open the connections between 1-2 and 3-4 with a switch. Or, note that 1v is enough to maintain memory contents, but stops the clock and other logic from drawing power.

Q: ....consider trying a NVRAM from Simtek (now Cypress Semiconductor) STK12C68 Series 64K-bit (8K-bit x 8) 5 V 300 mil DIP-28 AutoStore NVSRAM 45 ns. Or, a Dallas Semiconductor DS1225 [with mechanical mods].

A: The Membership Card has a 600-mil wide memory socket, but an adapter could be made for a 300-mil chip.... The DS1225 has a coin cell stuck on top of it, which adds to the height, and there is none to spare.

Off list, Herb Johnson suggested a little adapter board that accepts two modern surface mount chips, one RAM and one flash ROM. This would give you non-volatile storage with cheap modern chips. I didn't do this as I was deliberately restricting myself to "old school" chips and construction techniques.

One other point: Consider that an ordinary alkaline AA cell will deliver 250uA for over a year. That's enough to *run* the Membership Card! Are you sure you need nonvolatility longer than that? - Lee Hart, Oct 11 2010 on cosmacelf

data available: Q: Is there a way to signal external hardware when data is available at the output port? Worst case, I can greenwire TPB to a pin on the 30-pin connector.

A: The Q line can be used. Or use one of the 8 bits as a strobe, i.e. a 7-bit ASCII character with the high bit low, then write the same character with the high bit high. [TPB] could be done, [or] use INT or EF1-EF3, for example. - Lee Hart, Oct 23 2010 on cosmacelf

Errors, corrections, improvements

Here's a link to a Tech Note about drilling the Altoids can, the use of pin sockets, and other mechanical issues.

Here's a link to the Rev B schematic as of Nov 2010.

Oct 9 2010: Tim Green wrote:"Just got my Membership card Rev B working tonight. Q is blinking as I type this! I have the 8K Ram chip and the pin out table on the schematic is wrong. P2 needs a jumper on 3-4. The table shows it on 2-3. Other than that, it went together fine."

Tim continues: "I may have to come up with a breakout board that plugs in between the two original boards. Thanks for such a neat kit. I knew I had to have one as soon as I saw it on Hack-a-day. "

"Also, as I wrote on the Yahoo group, I replaced the RAM chip with a Dallas Semiconductor DS1225 nonvolatile RAM chip. I had one in my parts box and it just pops right in... sort of. It is a little bigger than the RAM chip. So I had to file on the edge of the CPU and sort of cram/force it in the socket pins. It holds the program without having to pull the I/O board off. The DS chip is way too tall for the Altoids tin, but I have a pipe tobacco tin I'm going to use anyway."

Lee responds: "Thanks! I like tinkering with robots. I bought a little 6" high R2D2 model, and am hacking it to put the Membership board inside it. It can directly drive some little stepper motors I found. "[A breakout board] could be done. A board placed in between them can use a female Molex connector like the Front Panel on the bottom, and a male pin header like the Membership Card on top. Though the Membership Card is fully functional without the front panel; your new board could simply replace the Front Panel with whatever you need. "One idea I thought of, was to make other Front Panel boards; maybe one with 7-segment LEDs and a little hex keypad like the Netronics and Quest Elfs. Another with a keypad and 1861 video output like the RCA VIP. Or, maybe a little alphanumeric LCD and cellphone-like qwerty keyboard! ;-)"

- courtesy of Lee Hart

Feb 2011: Chuck Bigham completed a Rev B kit in Jan 2011. Chuck has connected his Membership Card to a Windows PC with a PicaxeŽ PIC-based microcontroller with a serial link to the PC. Check his Web page for descriptions and his Windows (32-bit) compatible software to download and operate the Membership Card.

This page and edited content is copyright Herb Johnson (c) 2011. Contact Herb at, an email address is available on that page..