03 October 2012

EE Prototyping 3

There are several major projects that we're considering for the course.  Two of my favorite ideas involve taking stuff apart.  The first idea is just to collect a bunch of random electronic products and disassemble them to explore a variety of construction methods.
  • Printers and scanners
  • WiFi routers and ethernet switches
  • Cable TV boxes
  • AM/FM radio receivers
  • Laptops and cell phones (modern and ancient)
  • Heavy-duty adjustable power supplies
  • Function generators, oscilloscopes, and other lab equipments
The second idea is a focused effort in reverse engineering. The class will be split up into an even number of teams.  Each team gets a product that they have to reverse engineer and create a complete documentation package for, including schematic, bill of materials, and maybe even a working simulation (but no board layout and no pictures). Then, each team trades their documentation package with another team, and they have to build a working copy of the object just from the documentation (without ever seeing the other team's original).

My thought is to use cheapo guitar pedals for this project. The circuits are relatively simple, most use commodity parts, and they're fun.  Plus, when you're troubleshooting an audio project, in addition to looking at the waveforms on an oscilloscope, you can listen to it (and tell that something is wrong from the sound it makes or doesn't make). To get an idea of the complexity of this project, I went to my local Music Go Round shop, and bought all the pedals that I could find for less than $10.  Here they are, the lambs for the slaughter (with a couple others... the Boss DS-1 and Joyo JF-06 were a little more than $10).

I had the students in the seminar take them all apart and look at the circuit boards and the chips used. The Danelectro BLT Slap Echo has two boards, a switch board and a sound board.  The sound board has a PT2399 echo chip on it, which is no surprise.

The Behringer CS400 Compressor/Sustainer uses a lot of tiny surface-mount parts.

The Ibanez PL5 Powerlead uses all through-hole components on a single-sided board.

The Danelectro D-6 Fab Flange also has two boards inside.  The switch and amplifier board has some CMOS 4053 switches and some TL072 dual op amps on it.

The sound board uses a pair of BL3207 bucket-brigade chip (with a BL3102 clock driver chip)

The sound board in the Danelectro D-2 Fab Overdrive just uses a TL072 dual op amp and some passive components.

I think these will make great projects.

The reading assignment this week is Sections 9.5, 9.6, and 9.8 (Hardware Design Techniques: Thermal Management, EMI/RFI Considerations, and Breadboard and Prototyping) of the Analog Devices Data Conversion Handbook.


Ulf K said...

I think that you should include a small tutorial about Cirquit Board Layout software and it's uses. There are several inexpenceive systems available today and some of the big guns even have free trial versions (limited in the amount of components on a board) that can be used in training classes. With the right approach, the class will learn that a circuit board is a part of a modern apparatus design (because of signal integrity, timing etc). A few years ago I was informed that the middle age for askilled circuit board designer was 45+ and that the age increases every year. Not many newcomers take up this trade, since it requires both a good understanding of electronics, CAD-software proficiency and also a sense of how to make the boards look good.
Bear in mind that the gerber files (photoplot files) are called "Artwork"

Ulf K said...

Scrolling down and reading EE Prototyping II only to discover that what I suggested was already in the plans.