Knowing how output ports work on the GoGo Board

Power is the key

When you connect an output device such as a motor or a light bulb to an output port, you have to make sure you feed it with the right amount of energy. If you don't get this right, your output device will either not work or get burnt. The output ports on the GoGo Board put out 5 volts. The output ports usually have plenty of power, which means it can burn a lot of things. It is best to use output devices that uses the same voltage as the output voltage (5V). But if you plan to use a low voltage device (relative to the output port), you will need to block some of the this output power. This can be done easily with a resistor.

Reducing Power with a Resistor

You need to insert the resistor in series with your output device, as shown in the figure above, to reduce the output power. But before you do that, you need to know how much resistance to use. To know exactly, you will need to do some math. But in general, you can tinker around by starting with a large resistance (like 10k) and then reduce it down until you are satisfied with what you get. Using a potentiometer (a variable resistor) makes this process easier. In many cases, the lower the voltage rating of the device, the higher the resistance value you will have to use. The following table shows some examples (assuming the output voltage from the GoGo Board is 9V):

Note: The resistance you need may be very different from the values in this table, as there are other parameters that affect the amount of resistance needed. I am showing these numbers just to give you a rough idea.

Caution: When a low resistance is used (i.e. 10 ohms), the resistor often heats up. So you should make sure you:

• Properly wrap it with tape and avoid touching it.
• Use a resistor that has high power ratings. Normal resistors are 1/4 and 1/8 watt. Some times you need 1/2 watt resistors, which are a bit fatter.

Using Motors

You can find motors everywhere - at electronic stores, radio repair shops, or even in you old broken tape player. Most of these motors can be used with the GoGo board.

Different kinds of motors you can find

The important thing to know is the motor's rated voltage. As I've mentioned in the previous section, it is best to match this voltage with the output voltage from the GoGo board (9V). If you buy motors, you should obviously ask for the 9V ones. But if you have a motor and can't identify the voltage, there is no reason not to try it. Here is what you should do:

Tinkering with Your Found Motor

Follow these steps if you are using a motor that needs less voltage than what the GoGo board gives (9V) or if you don't know how much voltage your motor needs.

Note: you can use a potentiometer (variable resistor) instead of the resistor to speed up the process, as you can change the resistance without having to physically replace the resistor.

Once you have determined the right resistance value, you can solder everything properly.

Example of a motor with a power limiting resistor

Bypass capacitors

When driving inductive loads such as motors, the load sometimes generates noise back to the board. This noise can mess up the power of the board causing it to halt or reset. If this happens, you need to add a small capacitor across the motor leads.

A typical bypass capacitor size is 0.1uF (0.1 Micro Farad). Don't use polarized capacitors (i.e. ones that have one lead longer than the other).

*Note that GoGo board 1.5 and higher have built-in bypass capacitors on board.

A motor with a bypass capacitor (blue).

Using Lamps

First of all, lamps in this case are much smaller than the ones you see on the ceiling or in your desk lamp. If you want to control those high power devices, you need to use relays (see below). Here we are going to focus on small light bulbs and LEDs.

Lamp examples

Lamps

in the same way as motors, you should try to use lamps that are rated at the same voltage as the output from the GoGo board (9V). If they use less voltage, you need resistors. Lamps are more fragile than motors, so you should never test a lamp without a resistor.

LED (Light Emitting Diode)

LEDs are similar to lamps, but the light you get is much more directional. LEDs also consumes less power. Thus, they definitely need a resistor to reduce the power from the GoGo board. You should try something between 500-2000 Ohms.

LEDs

Summary: tinker with your lamps and LEDs the same way you do with motors, but NEVER try your lamps without a resistor.

Using Relays

Relays are very useful when you want to turn on or off high power devices (i.e. desk lamps, TVs, water pumps, etc). They are basically high-power switches that you can control with the GoGo Board.

The following diagram gives you a basic idea of how a relay works. You connect the output from the GoGo Board to points 1 and 2. This controls the magnetic switch that physically connects points 3 and 4 together. At points 3 and 4 you connect one of the high power leads.

[A relay diagram]

Wiring a relay circuit

Caution: Let me first remind you that you are about to work with very high voltage. Please make sure that there are no bare wires left anywhere on the circuit. Never allow children to work with relays without a supervisor.

Relays come in many shapes, but the most commonly used relays come in a rectangle box with five pins, as shown in the figure below.

[ image of a five pin relay - map pin 1,2,3,4]

Here are examples of other layouts that are commonly found.

[ image of other kinds of relay - map pin 1,2,3,4]

The following diagram shows an example of a typical relay circuit.

[ Relay circuit]

You can use a simple extension cord for the high power wires. Cut one of the wires and solder it to the relay.

[ diagram showing how to cut the extension cord ]

It is a good idea to solder the relay and the connections onto a perf board. Then you should screw the perf board onto a piece of wood or plastic. This way, you can hide away all the dangerous wires.

[ illustration of relay, perf board, wood base]

An example of a finished relay switch module.

Testing the Relay

Plug the control wires (1,2) into an output port on the GoGo Board. Then turn the port on (using any of the software libraries - see download page). You should hear the relay click. Turn it off and the relay should click again. If this doesn't happen, check the connection and the solder on the perf board.

Next, plug the high power wire into an outlet and plug a lamp (or any other electrical device) to the outlet on the other end of the wire. Now turn the output port on once again. This should turn on the lamp.

[image illustrating the test]