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Dizzy food

In de lunchbox    

A look inside

Building the feeder is easy, as long as you stick to the right sequence.


Food PCB

Start with the resistors, the 1N4148 diode and the socket for the 74HC00. Use the smaller of the two 330 ohms resistors in the package. Solder each component in place and cut its wires flush with their solder blobs before doing the next one. Double check the resistor values, using an ohmmeter when in doubt. (example: 100K can be brown, black, yellow, but brown, black, black, orange is also possible). Note that `330E' in the diagram means `330 ohms'. The black line on a diode marks the cross line in the symbol.
Do the variable resistor, the capacitors, the 78L05, the bridge rectifier and the transistors. You might like to ream out the holes for the BD442 a little. Make sure to put that transistor exactly in the position shown, with its hole matching the one in the PCB and its metal side facing upwards.
Cut two 40mm long pieces of tinned (not isolated) copper wire, and solder them into the LD271's mounting holes. Make sure that the variable resistor is centered (its arrow-shaped screw pointing towards the BC337).
Follow with the electrolytic capacitor, double checking its polarity; the minus is marked on the case, and corresponds with the `beaker' side of the symbol in the diagram. Finally push the 74HC00 in its socket, pin 1 facing the 10N cap (see photo below).
PCB top side     Food PCB

Into the box

Drop the PCB in the box. Lower a 3mm drill through the hole in the BD442 and drill through the bottom. Lock the PCB in position with one of the M3 screws. Drill the second 3mm hole. Take out the PCB and drill holes in the box for the connectors; 8mm for the DC connector, 6mm for the panel socket. Unscrew the panel socket's plastic parts and nut, then use your soldering iron to tin its hollow end - just a little tin will do. Cut a 110mm long piece of blue wire, strip the ends, twist and tin them, then solder one end into the panel socket. Not too deep; the plug will need some room as well, coming from the other end. Screw the frontal plastic part back on (the plastic ring is not needed), lead the wire through the 6mm hole and push the socket in position. Place the nut and tighten it (not too tight, or you'll break the plastic part). Cut two 40mm long pieces of yellow wire. Strip the ends, and solder one end of each into the PCB (holes near the bridge rectifier).
    Cut a 60mm piece of red wire, strip the ends and solder it into the hole near the BD442's center leg. Solder the blue wire connected to panel socket in the remaining hole, next to the red wire. Now push two M3 screws up through the hole in the box's bottom. Drop the 5mm plastic washers onto them. Then fit the PCB. Put a nut on the corner screw. Place the heatsink on top of the BD442 and tighten it down with a second nut.
Mount the DC connector, making sure you can easily reach its center leg and the one left of it (use the photos for reference). Solder the yellow wires onto these legs.
Inside the box     LED modification


This is best made using strips of wood measuring 44 x 5mm, a standard size available in any length that is likely to be practical. The 44mm is important, because an IR LED at 50mm above the terrarium floor is in the best position to be seen by Dizzy's IR-sensitive eye. And a lower terrarium wall might not meet his feelers properly. The prototype's corners were joined using hinges of the kind which can be easily unhooked.
The smallest usable size is perhaps 1 x 0.7 meters or so. Increasing the size beyond 2 x 2 meters may cause Dizzy to have trouble finding his food. The floor should be level, smooth and antistatic - like a sheet of wood.
After preparing the woodwork, it's time to cut the `dinner table'. Use a metal saw to cut a 200 x 200mm piece off the large sheet of PCB material. Bevel at least two of its edges, so Dizzy won't have trouble rolling onto his table. A sanding machine will do the work in minutes.
Cut a 100mm piece of blue wire. Strip both ends and solder one end to the corner that will be closest to the box, as shown above. Mount the blue plug on the other end.
Next cut off the vertical part of the `dinner table', matching the height of your terrarium wall. Consider in which corner of the terrarium you want the dining area to be. Clamp the vertical part against the inside of a wall near one end, and drill a 3mm hole though the PCB material and the wood. Then clamp the box against the outside of the wall, as shown by the photos. Put the drill in the hole and and carefully drill through the side of the box.
Push an M3 screw through a spring washer and through the holes in the PCB material, the wood and the box. Give it the washer with solder point and a nut. Drill the second hole, add a screw, washer and nut. Tighten up. Solder the red wire coming from the PCB onto the solder point.
Use a key file to modify the LD271 as shown above. This makes it less directional, allowing Dizzy to more easily find it.
The longer of the LD271's wires is its anode. Its cathode is usually marked by a flat side of its rim. Inside its case, the cathode wire ends in the larger structure, which holds the silicon (have a good look at the top photo on this page).
Solder the anode to the wire you soldered into the hole connected to the 78L05, and the cathode to the other wire, aiming the LD271 roughly at the center of the terrarium.

Slow charge procedure

To adjust the `dinner bell', we need Dizzy's help. So we must first charge his battery. The procedure is the one you should also follow if the battery should ever be really flat - which normally happens only if you store the robot for a few months or longer.
  1. Touch ground (metal part central heating) and take the AT90S2313 out of its socket, by carefully lifting it at both ends, using small screwdrivers. Place it on a non-static surface.
  2. Connect pins 2 (PD0) and 10 (gnd) of the socket, using a piece of tinned copper wire as shown left.
  3. Set Dizzy's power switch in the `on' position (toggle towards the battery).
  4. Stick one end of the 330 ohms resistor you've left into one of the feeler tubes, and position the robot on his `dinner table' as shown. Check that the other end of the resistor touches the vertical contact plate, and that one of the castors leans on the table itself. The feelers must not touch either plate. Connect de supplied mains to 12V adapter. You might check operation by measuring voltage across the resistor (around 7V).
  5. Wait between five and six hours for the battery to acquire sufficient charge.
  6. Remove the resistor and the bridge, switch off and carefully push the AT90S2313 into its socket (pin 1 closest to the switch).
Slow charge


Adjusting the `dinner bell'

Make sure there is enough light and put Dizzy in his terrarium, in the corner opposite to his `dinner area'. Make sure that the mains adapter is plugged in. Push the tip of the feeler closest to Dizzy's on/off switch some 50mm in any direction, switch on and let go of the feeler. This puts the robot in a special mode - it will respond to its feelers by moving away from whatever was touched, and when its IR receiver sees the IR beacon, it will beep almost continuously as long as the beacon remains in view. Try aiming Dizzy at the LD271. Move him closer if he doesn't respond. If you don't get a beep at 50cm, remove the black hood and use a small jeweler's screwdriver to adjust the beacon's variable resistor until you hear the beep. Turn the screw left until the sounds stops, then back and to the right until the sound stops again. Center the variable resistor between the points where the beep went away.
If you had to move Dizzy closer to get a response, then repeat the procedure with him sitting in the opposite corner. Then switch off the robot, unplug the adapter and desolder the LD271.
Drill a 6mm hole in the lid of the box, for the wires to pass through. Screw the lid on top of the box and solder the LD271 back in place. Plug in the adapter. Push the tip of Dizzy's other feeler some 50mm in any direction, while switching him on. This puts him in his second special mode; he will now try to find his `dinner table' and have a bite, whether he's hungry or not. If he makes it, then let him eat until he moves away from the table. If he moves towards the beacon without quite making contact, then aim the LD271 ten degrees or so away from the center of the terrarium. Experiment with the aim until the robot has no trouble making contact with his power source.



Ready to roll!

Switch Dizzy on, this time without touching a feeler. He will turn around his top axis until he is satisfied with his view. After looking at his battery condition for 20 seconds, he'll begin watching his environment. If you want him to pay attention to you, then put his terrarium in a dark corner, or well below the window.
Enjoy your Dizzy!

What to do if something's wrong?

If nothing at all happens, you probably made some small mistake. Switch off the robot, unplug the adapter. Check your solder points, wires, resistor values and polarities. You might ask me questions. If all else fails, you might carefully pack the robot and its feed box, and mail them to Pitronics, including your mail and email addresses. Best make email contact first, though.

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