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How to Use a Double Breadboard

Breadboards are made to temporarily hold test circuits. They do not require solder and are made from plastic. They are divided into two sections and have holes so that components can be inserted inside of them. These holes are arranged in columns and rows.

A typical solderless breadboard has one set of red and blue stripes at the top, and another set at the bottom. Next to each stripe are rows of holes that are all connected together. The red stripe is for inserting positive voltage connections, while the blue stripe is for negative or ground connections. Sometimes two breadboards are connected together to form a double breadboard. This is useful for testing components that require two input voltages to operate. These combination breadboards are also convenient for testing large circuits.

To use a double breadboard, pick its middle section and set one row as common ground for all of the components. This method can be practiced with a LED driving circuit that uses a transistor.

Things You'll Need

2N3904 NPN transistor
Red LED
1k-ohm resistor, 1
10k-ohm resistors, 2
9 V batteries, 9
Battery holders
Solderless breadboard
Jumper wires

Instructions

- 1
  Place the breadboard on a flat surface so that it is lying horizontally. The stripes should be at the top, middle and bottom. There will be two sets of stripes in the middle.
- 2
  Determine which of the transistor leads constitute the base, emitter and collector. This information can be gathered from the package, manufacturer's website or data sheet.
- 3
  Insert a jumper wire between the first and second blue rows. Do this by placing one end of the wire in one of the holes near the first row and its remaining end in one of the holes near the second. The two rows will be electrically connected and will form a common ground.
- 4
  Insert the transistor near the top of the breadboard. Each lead must be placed into a separate column.
- 5
  Set the emitter column to ground. Do this by adding a jumper wire between the emitter column and one of the holes near one of the blue rows.
- 6
  Attach the negative lead of the LED, which is the side with the shorter leg, to the same column that the base is in. The LED's positive lead must be placed into a different column. Insert the 1k resistor into the same column that this positive lead is in. If necessary, let the resistor straddle the breadboard's first and second sections. Add a jumper wire and connect the end of the resistor to the one of the holes near the first red stripe.
- 7
  Place the 10k resistor in the same column that the base lead is in. Use a jumper wire and attach the end of the resistor into one of the holes near the second red stripe.
- 8
  Attach the red lead of the first battery holder to one of the holes near the first red stripe. Attach its black lead to ground. Insert the red lead of the second battery holder to one of the holes near the second red stripe, and add its black lead to ground. The first battery supplies 9 volts to the collector, while the second supplies 9 volts to the base.
- 9
  Place the batteries inside the holders, and the LED will light. Replace the 1k resistor with the second 10k one. The LED will glow less brightly.

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