MECHANICAL CIRCUIT

Construction of the Mechanical Circuit

General Information

The orientation of the circuit board is always going to be white markings face-up and the copper markings will be face down. Points of attachment will be given like points on a graph where the origin is in the lower right hand corner of the circuit board. Notice on the circuit board that for easy refernce of the X-coordinates, at every fifth row the white marking has a flat edge to the oval. Complete all building instructions and the troubleshooting directions before testing the circuit board.

Step I - attaching the NPN and the two resistors

NPN
The NPN has the following shape with three metal wires coming off from the bottom side. Each wire has been given a coordinate as to where it is attached to the circuit board. It is important to position the NPN with the copper metal side or plate towards the top of the circuit board. Solder the wires to the back of the circuit board. It is OK for the NPN to stand out a little ways from the board. Do NOT have the NPN wires protrude a great distance beyond the board on the backside, because you will be soldering things into the the hole right next to it.
Resistors
There are two resistors that need to be added to the board. The coordinates for each end of the resistor are written on the illustrations below. The color bands on the resistor are important. It is essential to match the correct resistor with the right coordinates. There may be a fourth band on the resistors which is gold or silver. You can ignore this band; however, it is helpful in orienting the resistor to make sure you have the correct one. Place the gold or silver band on the right. If in doubt, look at the Figure 1 below.
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Step II - Attachment of three wires to the circuit

General Wiring Information
All of the following wires may protrude a fair distance behind the board. It is advised that you trim them to be within a millimeter or two of the back of the board. You will find that it makes it easier to solder the wire and get a better connection. Be generous with the solder; make a nice cone or volcano shape mound of solder to hold the wire to the circuit. Pay CLOSE attention to NOT allowing any solder to bridge from copper marking to copper marking on the back. It is OK for the solder to run along the same copper marking however. It would be helpful if you had a magnifying glass to check carefully that no solder runs between markings. If you should find such a bridge you will need to clean it up with a piece of copper wick (Chem-Wik). See appendix for instructions on how to clean up excess solder.
First wire - use a small purple piece of wire at coordinates (4,6) & (10,7).
Second wire - this is a very short piece of orange wire. It will be easier to work with and place in the board if you use the needle-nose pliers. Attach the wire at (10,9) & (12,7). There may be some difficulties in getting the wire to slide in the hole next to the terminal because it may be partially covered. Do the best you can--the wire must go in there in order to make proper contact with the terminal.
Third wire - this is a very short piece of yellow wire, that goes at the coordinate (16,7) and (14,9). [Note - If the resistor is making it very difficult and you find it easier, the second coordinate of the wire could also be (15,9)].

Step IV - attachment of the 30amp relay

When you take the relay out of its bag, notice that it is a black box. Take a small flat screwdriver and pry the top black square cover off from the flat bottom. It should reveal a copper coil.
With a pair of needle-nose pliers you need to bend all the metal tabs until they are parallel with the base of the relay. Three of the tabs will stick out beyond the edge of the relay; that's OK. Two of these tabs will be used to attach the relay to the board (see figure IIa). The relay attaches to the backside of the circuit board. When looking at it from the front, it will be in the middle of the left side (see figure IIb). To help attach the relay to the board you can put a little caulking on the tabs. The relay should be found within the following coordinates (17,5) (17,13) on the lefthand edge of the circuit board. The relay will hang over the edge of the circuit board slightly if you center it in the coordinates indicated above.
To attach the relay firmly to the board and to attach it to the circuit, you will connect two (2) wires. The two wires come from the jumper wire kit and are orange-colored. The first wire will come through the front of the board at (22,15) and pass through the hole in the metal tab. Attach the second wire at (22,3) in the same fashion. Take the extra wire that protrudes on the backside and bend it, with the needle-nose pliers, to cross over the neighboring metal tab. Solder the wire to the metal tab. The metal tab is so large it acts as a heat "sink," and so, when soldering the wire to the tab, you must hold the soldering iron to the tab for awhile. This allows or enough heat between the wire and the tab to make sure there is a good joint. If the solder looks dull, then you need to heat

Step IV - attachment of the potentiometer (10k ohms) and the PC board terminals

Potentiometer
The potentiometer should be glued to the board with silicone rubber (the type used for caulking is fine). The glue is spread all over the bottom surface of the potentiometer (the flat side). Put four dots on your board with a pen at the following points - (9,17) (17,17) (9,10) (17,10) -glue the potentiometer to the board within these points. The bottom edge is the most important. Don't let it go below the 10th line. The caulking takes 15 minutes to dry enough so it won't slide on the board.
PC Board Terminals
You will notice that the PC board terminals come in three units. Separate one unit from the group. The single unit will be attached to the right edge of the circuit board. There will be two pins on the back of the unit; the pins should go through the board at the following points - (1,8) (1,10). LOOK at figure one to see how to orient the unit. The screws should be towards the edge of the board. The unit should be soldered to the circuit board (on the copper side of the board). See Appendix I for directions on how to solder. The other two-unit piece will be attched at the center, lower half of the board. The coordinates for the pins will be as follows - (10,5) (12,5) (14,5) (16,5). You should find that as soon as you place the first pin the other pins follow naturally in the remaining coordinates. Again the screws should be oriented towards the bottom edge. Make sure when you're doing the terminal units that you find the coordinates on the FRONT side of the board. Solder the double unit to the board.

Step V - attachment of additional wires to finish the circuit

Fourth wire - use a brown wire that goes from coordinate (3,2) to (7,8). Putting a small arch in the wire will make it slightly easier to "fit in" over the top ofthe resistor.

Fifth wire - use a small BLUE piece of wire at coordinates (1,12) & (5,9).

Sixth and Seventh wire - these wires will connect your PC board terminal (single unit on the right side) to the potentiometer. The wire used to do this can be from the jumper wire kit (long yellow or green would be OK) or you can take a piece of the wire from the AC power adapter. If you if you decide to do the latter, take the adapter out of its case and CUT the plug off (The part that you would normally plug into the appliance, NOT the large black box part). At this point cut off a small 6 cm piece. Set the adapter aside now; it will be the final part you will attach. The adapter wire is actually two wires. Carefully split the two wires at either end. You will notice there is an all black wire and a wire with a stripe. Attach the all black wire (or yellow or green jumper wire) at the following coordinate (5,8) to tab B of the potentiometer (see figure I for which tab is which). The wire with the white stripe attaches at coordinate (4,7) and to the tab A of the potentiometer.

Eighth and Ninth wire - these orange wires are already partially attached to the relay. Take the wire that starts at coordinate (21,3) and attach the other end at coordinate (2,2). (Note - take the wire around the NPN or around it toward the bottom edge of the board - See figure IV). Take the wire that originates at (24,16) and is already attached, and attach the free end to coordinate (8,9).

AC Power Adapter - Take the adapter, minus the plug, and separate the ends of the wire. (If your adapter isn't without the plug, check directions for the second & third wires to see what you are cutting off). To attach the adapter, a small Phillips screwdriver is needed to open and close the screw that holds the wire to the terminal. The all-black wire goes in the top slot of the terminal that is on the right side of the board. The wire with the white stripe goes in the second bottom hole on the same terminal.

Step VI - Building the photogate attachment and attaching it to the circuit board.

Photogate attachment
Take the 4-wire phoneline cord and cut the wire about 20 cm from one end. Take the cut ends of both pieces and peel the gray plastic coating back from the wire. There should now be four colored wires exposed: yellow; green; red; and black. Again for both pieces of phone cord, use wire strippers and strip about a centimeter of wire clean. Solder the ends of each of these wires. Soldering will help the wires from fraying and make a better connection with the terminal. The two ends of the phone cord with the plastic male clips can now be plugged into your 4-wire inline coupler. The coupler allows you to move your photogate or roach track without disturbing the circuit board and the drum. The short piece of telephone cable (exposed wire end) is now attached to the two-unit terminal found in the center of the board. From LEFT to RIGHT the wires are attached (with the aid of a Phillips screwdriver) in this order to the holes in the terminal: yellow, green, red, and black. Make sure that none of the wires can be GENTLY pulled out. If they can be pulled out the connection is too loose and the circuit won't work.
At the loose wire end of the long piece of phone cord, peel the gray wire back so about 4-6 cm of each colored wire is exposed. Using wire strippers, strip each colored wire. Take the high-output infrared LED and attach the yellow and green wires to the metal tabs. The yellow wire attaches to the metal tab that is next to the flat side of the plastic LED. The green wire attaches to the rounded side. The red and black wire attach to the infrared phototransistor. The red attaches to the rounded side and the black attaches to the flat side. If you have heat shrink tubing it would be good to cover the above junctions to help protect them. See figure Vb below for an illustration of the setup. After completing the troubleshooting section, assuming the circuit works, take the LED and the phototransistor and line them up directly across from one another. In the cockroach application it was found that placing the pieces in a vertical arrangement works better than a horizontal, otherwise the cockroach can slip underneath the beam. Orienting the beam vertically is more likely to hit the flat, broad surface of the cockroach.

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