Technical Projects







Fabrication Building your own Atmex board

The Atmex board can be built by anyone who has even the most minimal soldering experience. All parts are through-hole, and the board only has 16 components to solder. It is also fairly inexpensive, costing less than $10

Purchasing components

The first step to using Atmex is to build an Atmex board! All the components are available at Digikey. Making one PCB is not viable, but you can make approx. half a dozen for reasonable cost (<$50) at 4PCB/Barebones or Olimex. See the download page for gerber files.
Name Manuf. Part Number Description Cost per (qty 25) Total Cost (qty 25)
IC1 Atmel ATTINY2313-20PI Microcontroller $2.26 $1.43 $2.26 $1.43
IC2 T.I. MAX232N RS-232 level shifter $0.78 $0.65 $0.78 $0.65
IC3 Any 78L05 5V fixed regulator $0.20 $0.17 $0.20 $0.17
SW1 Omron B3F-3120 Reset button $0.30 $0.27 $0.30 $0.27
X1 Norcomp 171-009-202-001 Serial DB-9 female $0.67 $0.58 $0.67 $0.58
X2 CUI PJ-202AH 2.1mm Power jack $0.38 $0.33 $0.38 $0.33
X2 Alternate CUI PJ-600A 2.1mm power jack (vertical) $0.45 $0.38 $0.45 $0.38
D1 Any 1N4001 Protection diode $0.03 $0.03 $0.03 $0.03
LED1 Lite-On LTL-1KHPK or (LTL-4266N) Red LED $0.11 $0.09 $0.11 $0.09
C3,C4,C5,C6 Xicon 140-MLRL50V1.0 4 x 1uF Capacitors $0.08 $0.06 $0.32 $0.24
C1, C2 Panasonic ECE-A1EKA220 2 x 22uF, 25V+ Capacitors $0.16 $0.10 $0.32 $0.20
R1 KOA CFS1/4L151J 150ohm resistor $0.02 $0.02 $0.02 $0.02
IC1* AMP 390261-6 Socket for IC1 $0.15 $0.14 $0.15 $0.14
PCB           $7.50 $5


Supporting Hardware
You might want to also buy one each of the following, to power and communicate/program the board. Most are already available in labs or workshops, but you might want to own a set for yourself. Any positive-center 7-12VDC adaptor should be just fine, as should any reasonable-quality PC serial cable or USB/Serial converter.
Description Manuf. Part # Cost per (qty 25)
2.1mm plug Kobiconn 170-2110 $0.57 $0.44
Alkaline 9V Battery Energizer 9V $2.00 $1.88
9V snap connector EPD 123-5006 $0.33 $0.30
9V DC adaptor, 2.1mm plug CUI DPD090020-P5P $3.68 $2.94
2m serial DB9 cable Generic 6' M-F DB9 Cable $2.30 $2.07
USB/Serial adaptor for Macs, etc. Keyspan/etc. USB/Serial $17.95 $14.55
Soldering Notes
The Atmex board is about as simple as any board you'll solder, but has some interesting points to note, especially for beginners.
  • The (arguably) most important component to get right is the protection diode, D1. This is the component that protects the rest of electronics from plugging in the wrong power supply. Getting this part wrong will result in fried chips and much sadness. The 'arrow' in the picture points to the white stripe on the diode.
  • The electrolytic (cylindrical) capacitors also have polarity, the white stripe on the capacitors indicates the negative terminal. Whereas the pictures on the board indicate the positive terminal hole.
  • The LED and voltage regulator should go in the way that matches their shape in the picture
  • The DB-9 connector is kind of funky, it sandwiches the board between the rows of connectors. To keep it secure, make sure it fits snugly right against the board and use lots of solder on every pin.
  • Solder the MAX232 chip right in, keeping the notch on the chip lined up with the one in the picture
  • Solder in the socket for the Atmel, also noting which way the notch goes. I don't suggest soldering in the chip directly.
  • There are two options for the power plug, either one that is horizontal (alongside the DB9 connector) or vertical (points up from the board). Horizontal is more convenient and works with the CUI wall wart specified above, but some bulky connectors might not fit as well.