Has anyone found ordering information or the schematic referred to on Page 620 of Learning the Art of Electronics?

Page 620 of LAoE says, "The keypad is not a standard commercial part. See Appendix E for ordering information and Appendix 14N.20 for the schematic, in case you want to build your own."

However, Appendix E doesn't mention the keypad. The digital parts list on the LAoE website (link below) says, "See LAoE website" but there the trail goes cold; the website gives details for ordering the LCD but not the keypad (as far as I can see).

Also, Appendix 14N.20 doesn't seem to exist, nor the schematic for the keypad.

So the questions are:

  1. Has anyone found ordering information for the LAoE keypad?

  2. Has anyone found Appendix 14N.20 or the schematic for the keypad?

  3. Can anyone suggest an alternative approach to providing the keypad functionality which includes: controlling lines D4 to D14 of an XC9572XL counter; and writing 8 bit values to RAM via a 74HC541 octal 3-state buffer.


  • \$\begingroup\$ You may be 20yrs too late for that technology What version of LAoE \$\endgroup\$ – Sunnyskyguy EE75 May 5 '18 at 16:36
  • \$\begingroup\$ 2016 3rd printing with corrections 2017. It is the up-to-date version of what they used to call the Student Manual, so it's the lab course for the 3rd Edition of Art of Electronics... ...but they're a bunch of great old geezers! \$\endgroup\$ – David1 May 5 '18 at 16:52
  • 2
    \$\begingroup\$ You should write the authors and ask. Or have you, already? They have a web site and a way to initiate contact. Also, perhaps the course is being actively taught and you could contact the instructors or their support staff about it. Finally, regarding "geezers" you may notice that (1) the book you are discussing refers to the 8051 in the context of that keyboard so you have to admit all this truly goes back a ways; and, (2) some folks here also are in that category! (I have a box of 100 of the 80C32 here.) \$\endgroup\$ – jonk May 5 '18 at 17:09
  • \$\begingroup\$ @jonk Yes I've left comments on the website contact and Tom Hayes has responded in the past (very quickly) but not yet on this issue, which makes me suspect I've missed something (so perhaps he only responds when you spot a genuine error) or perhaps he's otherwise engaged. Yes, I do like old geezers (being near to qualifying for that category myself!) \$\endgroup\$ – David1 May 5 '18 at 17:48
  • 1
    \$\begingroup\$ I've also initiated contact at that web site. Just to add to the "noise" he has to deal with. If he responds, I'll let you know. If he does, he may decide to respond to you, first. Who knows? Anyway, I've added my pressure to yours. Other than that, that keyboard is probably just a simple 4x4 scanned keypad. It's not hard to make one of those work. Are you making that big board??? \$\endgroup\$ – jonk May 5 '18 at 18:14

There's a schematic of the keypad in the old Student Manual at the end of Chapter 15. Not sure what the disembodied U4c bottom-centre means, but it can't be that hard (famous last words!)

Update on 20 June 2018:

The author, Thomas Hayes, has been away on vacation but has got in touch to say he will put up-to-date details of the keypad on the Learning the Art of Electronics website. It is different from the one in the old Student Manual as he has re-designed it with a microcontroller in place of the many IC's of the older version, to do keypad scanning, switch de-bouncing and display.

  • \$\begingroup\$ Can you show a picture? \$\endgroup\$ – Dorian May 8 '18 at 10:27
  • \$\begingroup\$ Not sure about copyright but if you Google "student manual for the art of electronics" someone has pirated the whole thing... \$\endgroup\$ – David1 May 8 '18 at 17:54
  • \$\begingroup\$ Finally got it. Strange, U4c and U4d are two unused AND gates from an quadruple two inputs AND 74HC08. I don't find where are the other two, a and b gates, used. Unused CMOS gates inputs must not float so they are tied to GND. \$\endgroup\$ – Dorian May 11 '18 at 13:35
  • \$\begingroup\$ Hi Dorian, yes I got there in the end. The rest of U4 (a and b) is connected to [10] ADR CLK. I'm trying out a tiny circuit first for an electret microphone to see how easy or difficult it might be to build the keypad. It's my first move from breadboard to prototype board and it's a whole new world! \$\endgroup\$ – David1 May 12 '18 at 13:54
  • \$\begingroup\$ It's pretty dificult for a beginner, I wouldn't bet on my skills to make-it wotk from the first shoot. I see that this book is so popular that somebody should have mercy on students learning from it and design a cheaper, easyer to buildt diy keyboard using today's technologies. I will think about it. Leave the answer open one more week. \$\endgroup\$ – Dorian May 12 '18 at 16:02

Ok , here it is ,a quick and fast build for the keyboard, if you're familiar with Arduino it shouldn't take more than 30 minutes and 12$ if not then at most one hour.

The drawback is that it requires a PC to work , the advantage is that the money are not lost after you finish the book, you can reuse Arduino and the jumpers for further projects.

The project uses Arduino and a PC with serial terminal, an old phone with OTG might work to after uploading the program

Find here the entire project.

By the way, the idea of using Arduino is not inspired form the other forum where you asked this question, even I almost hate Arduino as a development platform I must admit that it's the fastest way for a beginner to make something work and from different options that I had, overall, this one was the cheapest, easiest and best documented option.

  • \$\begingroup\$ Thanks Dorian and I will give this a go in due course although as the update of 20 June below, the author has made contact and I've agreed to buy one of his custom made keypads. Not paid for it yet but agreed is agreed... \$\endgroup\$ – David1 Jul 7 '18 at 16:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.