September 7th, 2010 - How to build DM001

Simply speaking DM001 is a device that takes measurements of the Galvanic Skin Response of two people. These different streams of data are then mapped onto two different motors. Each person is able to feel the fluctuations in skin conductivity of the other.

We have designed a circuit to be etched on a pcb board that does half of the work. We have also written the Arduino sketch that does the other half of the work. Below you’ll find instructions to build DM001. If you have any questions you can always contact us at (Aktiviere JavaScript, um die Email-Adresse zu sehen)

DM001 in the exhibition Unleashed Devices at the Watermans

////////// COMPONENTS AND MATERIALS \\\\\\\\\\\

We can’t give you a full list of the tools but it is surely hand to have the following at hand: solder iron & solder, (manual/mini) drill and very small drill bits for the pcb holes 0.4 to 0.8 mm, stanley knife, metal ruler, some fine sanding paper, long nose and side cutting pliers.

1 x PCB 150 x 110 mm (large scheme) or 100 x 75 mm (small scheme)
1 x Arduino Duemillanove
1 x Power Adapter/Wall Wart (that can provide 5v with 1 amp, the center pin has to be the positive)
1 x PCP Mount Power Socket (such as http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=487-836 – make sure the pin layout matches)
2 x transistors (We BD677A used but any Transistor with same pin layout and similar power rating should work)
2 x 330K Resistors
2 x 1k Resistors
2 x Diodes (we took switching diodes like http://www.maplin.co.uk/Module.aspx?ModuleNo=46386)
4 x Potentiometers (such as http://www.maplin.co.uk/Module.aspx?ModuleNo=2205)
4m of flexible wire (we took some black 2 core wire with 0.25 mm cores, but any cheap speaker cable should do)
2 Pin strips (such as http://www.maplin.co.uk/Module.aspx?ModuleNo=1500)
Some Bell wire for the “air wires”
Some small nuts and bolts to fix the transistors on the board.

////////// STEP 1. ETCHING THE PCB BOARD \\\\\\\\\\\
The first thing you need to do it to download the schematics of our circuit and etch it on a PCB board. We have designed it in two sizes: 150 x 110 mm (large scheme) or 100 x 75 mm (small scheme).

DM001 Scheme Large

DM001 Scheme Small

There are already good resources online on how to etch a PCB board. We followed these two: http://opensolarcircuits.cc/?p=312 (in Spanish) and http://hackaday.com/2008/07/28/how-to-etch-a-single-sided-pcb/ (in English).

OUR ADVISE:
– We used transfer paper.
– Pre-heating the board with the iron for 5 minutes proved to be helpful.
– Be patient with the ironing. The longer you do it, the better the ink sticks to the copper, and the more reliable the whole circuit will be eventually.
– To remove the ink once the PCB board has been etched, we used a paint and varnish remover, since we found out that alcohol wouldn’t be enough.

////////// STEP 2. DRILLING HOLES \\\\\\\\\\\
Once the board is clean and we are sure the circuit looks reliable (all copper lines are think enough to conduct and there are no gaps or disconnections) we start drilling the holes for the components. The board is easily perforated with a small manual drill.

////////// STEP 3. SOLDERING COMPONENTS \\\\\\\\\\\

To solder a component onto the board:
1- Insert its legs through the right holes. The component should sit on the printed side of the board.
2- Bend the legs under the board.
3- Solder making sure the copper and the legs of the component are well connected. [link to soldering tutorial]
4- Cut the legs under the board.

REMINDER: There are two components that need soldering in a particular direction: the diodes and the transistors. The picture above should help you soldering the components in the right position.

Diodes:
The diode should sit with the anode(+) to the left and the cathode(-) to the right. Diodes are usually marked with a black ring on the cathode side.

Transistors:
Not all transistors have the same pin layout. The board is designed to work with transistors that [SPECS]

Air Wires:
You’ll have to solder some air wires to finish the board. Please download the following plans that will help you to find the right connections.

DM001 Scheme Large Air Wire
DM001 Scheme Small Air Wires

BEFORE YOU SOLDER THE STRIP PINS: To make sure that the arduino fits smoothly under the board it is best to place the strip pins on the arduino first and then solder them onto the board.

////////// STEP 4. TESTING THAT IT WORKS \\\\\\\\\\\

Next step is to connect the motors to the board, connect two pins to take the GSR readings and plug the board using the Power Adapter. In order to test whether everything works you’ll need to download the DM001 Arduino Code (pde) and upload it to the board.

Connecting the motors and the GSR pins