Tail Wagging Electronic Circuit Assembly
Note: If you purchased the circuit board assembled
you can skip this part.
Introduction
The electronic circuit serves the purpose of giving the magnet on the pendulum a little “boost” each time it passes over the coil. The effect is similar to the small “push” it takes to keep a child swinging on the swing. If the timing is right, it only takes a slight nudge to keep the swing going.
That’s what happens when the magnet passes over the coil. As it approaches the coil, it triggers a transistor, which turns on a second one that then induces a small amount of current into the coil. That current is induced just as the magnet passes over the coil. The result is that the coil, now an electromagnet, for just a short time pulls the magnet until it crosses the center and then turns to coil off letting the pendulum swing by with just a little more energy then it had before to keep swinging.
This circuit can run on solar cells which are available for around $10. They need to be placed around 8 – 10 inches from an incandescent light or in direct sunlight in order to work. This design has a switch that allows you to install both so you can use a battery when light isn’t available. An interesting project would be to make the base of the carving part of a table lamp with the solar cells mounted close to the light. Then when it is turned on, the tail would wag.
Electronic Circuit Assembly
Where you start next on this project is
determined by whether you purchased the
electronics kit or not and whether it was purchased assembled or not. We’ll cover
both of those options. If you purchased the kit
assembled you can skip down to the Final
Assembly section.
Figure 1 shows the components required to
make the swing circuit. If you choose to build the
circuit from the components without the circuit board, you should at least use some sort of prototyping board available from Radio Shack. Depending on the board you get, you will need to connect the components in the board as shown. A schematic of the circuit is shown in Figure 2.
Although you may not be familiar with schematic diagrams, for those who want to know what is involved, the schematic is shown in Figure 2. The diagram also shows a solar cell if one is desired. It can be added by connecting the negative terminal from the cell to the negative terminal on the circuit board and connecting the positive terminal to the other available pin of the switch. The switch (Sw) on the diagram) is what is called a single pole, double throw switch, meaning that it will turn the batteriery on in one direction and the solar cell when switched to the opposite direction. If you look at the diagram, you will see that when the switch is as is shown, it connects the battery to the circuit board. If the toggle is switched, the switch will connect to the solar cell. The solar cell position is used as “off.”
Circuit Board Assembly
Figure 3 shows a completed circuit board with all parts mounted and soldered. The coil is is placed directly beneath the magnet. When the magnet swings across the coil, the circuit switches the transistors resulting in the “pull” to ke the magnet swinging and the tail wagging.
Note there is no direct connection between the circuit board and the carving. The only connection is magnetic. Therefore you only need to place the circuit board coil under the magnet and turn the switch on. You may need to give the tail an initial push to start the swinging. If you’ve purchased an already assembled board, you can skip this part. However, assuming you want to build it, lets start.
The circuit board is the 2 x 3 in. board with copper trails on one
side. The side with the copper is the bottom. The copper trails
are actually the “wiring” to which you solder the parts. Parts
are pushed through the holes from the top and soldered on
the bottom of the board.
You’ll need a fairly small soldering iron to solder the pieces to
the board. In Figure 4, you can see why the iron must be fairly
small. To get a good joint, the iron should be touching the part
and the copper pad on the circuit board. Then touch the solder to
the spot where the iron intersects with the copper and the part
and let the solder melt into that joint. Avoid touching the solder to
the iron only, since the solder may melt but not make a good
connection between the part and the circuit.
Figure 3 shows the top of the board with all the parts attached.
Although the parts you have may not look exactly like those
shown, they will closely resemble them. Now if you have the
ciruit board, look at the underside of the board. Notice that one of
the edges is marked “top.” When you have identified the top, on the copper side, that edge will also be the top of the non non-copper side as shown in Figure 3.
Start installing parts by following the placement in Figure 3. There is also a diagram of all the parts with labels in Figure 5. At the end of this article is a duplicate sketch of the parts close to actual size. If you like you can print that sketch and put it over the circuit board to help locate the holes for the parts.
Notice that there are 2 larger round items called capacitors on the left side of the board. One is marked 1000 mf and the other 3300 mf. Notice also that both have a “-“ symbol on the side near one of the wires. The 3300 mf capacitor goes through the holes closest to the top with the negative (-) wire in the left hole. The 1000 mf capacitor goes into the holes underneath the other one with the negative wire also going into the left hole.
The diode is the small round glass object with wires
on each end and a black ring near one end. Place it so the
black ring is towards the bottom hole. Directly below the
diode is one of two resistors. The resistors just below the
diode are color coded brown, black and yellow.
There are two transistors. One is painted green on top
and the other orange. The orange one goes closest to the
top in the position shown in figures 4 and 5. Make sure the
flat side of the transistor matches the flat spot shown in the figures. Insert the green-topped transistor in the three holes in the position shown.
The LED is a red dome shaped plastic part. You will note t
hat there is a small flat spot on the bottom rim. The LED
should be inserted so that the flat spot is facing the left
side of the board.
The coil is somewhat delicate because the wires are
very thin. Glue the coil with 5-minute epoxy or double
faced tape over the copper ring on the bottom of the board.
Make sure the coil is turned so that the two wires are
closest to the holes through which they will go. After inserting the wires through the holes, pull most of it through so no loose wire remains on top. The wire ends are tipped with solder so that they can be soldered to the copper pads. After soldering, put a small bit of epoxy on the wires on the top and bottom where they are loose. This will protect them from being moved and broken. The magnet will swing quite close to the coil so you don’t want any loose wires where it can catch on them.
Finally, you will need to connect the battery holder to the switch and both to the circuit board. The configuration is shown in Figure 6.
The center wire from the switch is connected to the positive terminal (marked “+” on the copper side of the board). Either of the two outside terminals of the switch can be connected to the Positive terminal (+) from the battery holder. Finally, run a wire from the negative (-) terminal battery holder to the negative point on the circuit board as shown in Figure 6.
The other terminal on the switch can be connected to the positive terminal of a solar cell if desired. The negative terminal from the solar cell is connected to the other pad marked “-“ on the circuit board. With the switch in one position the battery is active and when switched the other way the solar cell will be active.
That should complete the electronic assembly. Now you will need to determine which side of the magnet needs to face the coil in order for the swing action to occur. Mark one side of the magnet with a magic marker and then put it on the coil, a bit off center. Then turn on the circuit. If everything is working the magnet will either pull into the center of the coil or fly off. If it flies off, and you remembered which side you had up, turn it over and do it again. When the magnet is pulled into the center, install the magnet to the pendulum mount in that position. Remember which side was up and with double faced tape, stick the magnet to the dowel mount.
Final Assembly details are in the next section of this instruction manual. You can get them in the link “Final Assembly” located at: http://genada.homestead.com/Products_animated-dog-info.html
Parts List for Electronic circuit.
All parts except the circuit board can be purchased either at http://www.LivinfArtInWood.com or from http://www.solarbotics.com/
Solarbotics is anexcellent resource for snimarion parts and supplies. The circuit used in this project is the same as the one used in their “SunSwingner.”
Printed circuit board – available from this web site. This project may be assembled with proto type boards from Radio Shack but it’s tough.1. Capacitor – 3300 mf
2. Capacitor – 1000 mf – both of these are available at any electronics parts supply, or Radio Shack.
3. Coil – the only place I know of that has these is http://www.solarbotics.com/. In fact all the parts in this kit can be purchased from them. The circuit used in this article is a modification of on they publish and they deserve the credit. They are a great place to visit on the web.
4&5. Two Resistors – A 100K and a 38K resistor. Available from any electronic parts store.
6. LED – any general purpose LED can be used, also available an any parts store.
7. Transistor – 3904 or 2N3904. This is a general purpose NPN transistor.
8. Transistor – 3906 or 2N3906. This is a general purpose PNP transitory. Get from any electronics parts store, Radio Shack carries them.
9. SPDT Switch. This is available at Radio Shack.
10. Battery case – A battery case that holds a single AAell. Also available to Radio Shack.
11. 1N914 diode – This is a general-purpose diode; you guessed it – Radio Shack.
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