tinkertoy

In this recipe we control a toy car using Flash so that instead of pressing the remote control buttons with our finger, we send the press commands from Flash. We build a small electronic unit that transmits the commands from Flash, through the Wiring board, to the hacked remote-control unit. To do this we use a unique electronic chip called an optocoupler.

Concepts and techniques in this recipe:

What is an optocoupler Tinkering with a ready-made electronic unit Controlling an on/off switch without physical contact

Parts and Tools

Wiring Board RC toy car 4 Optocouplers 1 Resistor (380 Ohms) Proto-board Heat Shrink 2 Pin Connectors Wire (Green/Black/ Red) BEFORE YOU START make sure to have all the parts and tools you need for this example.

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1.a The proto-board

There are two different sides to the “1000 holes” board: one side is made out of plastic and the other is covered with a metal layer.

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1.b Cut a piece of proto-board

Cut a 5.5cm X 2.5cm (2.16 X 1 inches) piece of the proto-board. The best way to cut the board is to use a metal saw.

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1.c Metal side

When we solder we always use the metal side.

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2.a Optocouplers

Optocouplers are great for tinkering. They enable you to control one circuit from another circuit when there is no electronic connection between the two circuits. In this recipe we will use an optocoupler to control an electronic unit - the remote control car - from another circuit - the Wiring board. How do optocouplers do this? When power and ground are applied to legs 1 & 2 of the optocoupler, legs 4 & 5 close a circuit between them. This is done using an LED (light emitting diode) and a light sensor that both sit inside the chip. When legs 1 & 2 receive power the LED emits light; the light sensor detects this and closes the circuit between legs 4 & 5. In the picture on the top you can see the optocoupler in its two states - without and with power to pins 1 and 2.

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3.a Place the optocoupler on the board

Take one of the optocouplers and place it on the piece of board you cut. The body of the chip should be on the plastic side, while the legs should penetrate the proto-board and protrude out of the metallic side. Place leg 1 so that it is facing left when viewed from the top; this means that leg 1 is closer to the edge of the board.

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3.b Solder the legs to the proto-board

Solder all six legs to the board. Make sure you are soldering only the leg and the metallic ring around it. If this is your first soldering experience, we recommend that you to read our soldering guide page before starting.

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3.c Soldering

If your soldering is too big, it can touch the other legs and cause a short circuit (and that is not a good thing!). Keep it small and neat.

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4.a Place all four optocouplers

After soldering the first optocoupler, place and solder the other three to the board in the same orientation. Leave a space of two holes between each two optocouplers as shown below. After soldering all four optocouplers to the board its metal side should look like this:

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4.b Ground wire

We are going to use black wires to connect all the optocoupler ‘ground’ legs (leg 2) to the ground (SOUP recipes always use black wire for ground). Cut three short pieces of wire and a longer one. Solder them as shown below.

The metal side should look like this. Notice the way we soldered the wire using three vertical points, connecting them in one vertical line. This way, the ground wire makes contact with the ground leg of the first chip and also connects to the next chip.

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5.a Resistor

Solder a 390 Ohm resistor (orange, white, brown, gold) to the end of the ground wire going out of the board. (why? because we say so). Solder another piece of black wire to the other side of the resistor.

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5.b Heat shrink

In order to prevent the resistor or the wires from touching something else and causing a short circuit, cover exposed areas with isolating tape or a heat-shrink tube. At the end of the ground wire (after the resistor) add a connector that can attach to the Wiring board pin.

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6.a Data wire

From pin 1 of each optocoupler connect a green wire. We will refer to this as the ‘data wire’.

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6.b Data wire - solder side

This is how the metal side should look. Make sure the data wires (green) are not touching the ground wires (black).

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6.c Data wire connector

Insert the four ends of the data wires into a connector.

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