Wednesday 6 November 2013

Class Notes; #2 Using Breadboard for the Flashing LED Circuit


Teachers having to train themselves for the new English Computer Science syllabus, have a lot to learn in a short time.

 

Many have no experience of handling and working with electronic components, as I recently discovered.


So this post expands upon my earlier post: How To Drive LEDs From A RaspberryPi, and is taken directly from my class notes produced for young Computer Science students.


Using Breadboard

In electronics, breadboard is used to quickly construct a circuit for experimentation or prototyping.
It is never used as a permanent or final circuit board in electrical products.

The holes in the breadboard are like miniature electrical sockets, and are designed so suit most common electronic components including resistors, capacitors, diodes, transistors and integrated circuits.

Some of the holes on this breadboard are joined together, so it is important to know which are, and which are not connected.

Left-hand side “+” column holes are all connected to each other, but not to anything else.
Left-hand side “-” column holes are all connected to each other, but not to anything else.
Right-hand side “+” column holes are all connected to each other, but not to anything else.
Right-hand side “-” column holes are all connected to each other, but not to anything else.

These “+” and “-” holes are generally used for external power supply connections.

The left-hand numbered rows are connected as follows:-
1a, b, c, d, and e are linked to each other, but not to anything else.
2a, b, c, d, and e are linked to each other, but not to anything else.
...and so on for each numbered row up to 30.

The right-hand numbered rows are connected as follows:-
1f, g, h, i, and j are linked to each other, but not to anything else.
2f, g, h, i, and j are linked to each other, but not to anything else.
...and so on for each numbered row up to 30.

 

Wiring the Flashing LED Circuit

This is an experimental circuit for use with the RaspberryPi.

Note: although the breadboard numbers and letters are not important, we are going to use them for reference when building this circuit.

Hold the LED so you can clearly identify which is the longer of the two leads (legs).


Carefully press the LED into the breadboard so that the longer lead goes into hole j10 and the shorter one into j11.

The LED leads are the same “pitch” as the holes, so they do not need to be bent.


Now take the 220 Ohm resistor and hold it between thumb and fore finger. Carefully bend one lead over your thumb nail to create a 90degree bend. Turn the resistor around and do the same with the other lead. You should leave a straight section of lead close to the resistor body.

The leads on your resistor should now be parallel, roughly the same length, and look a bit like this.


Insert your resistor into the breadboard so that one lead is in hole i10 and the other is further down the board in another “i” hole, like this.


My resistor is in i16 but yours may be slightly higher or lower, depending upon how you bent the leads.

You can now plug in the two jumper leads so that one is connected to row 10 (I've used f10) and the other connects to the end of the resistor which is NOT connected to the LED (I've used f16).

Remember the golden rule in Engineering: “IF IN DOUBT, ASK!”

Now get a friend to check your circuit.

If its OK, you are ready to connect it to the RaspberryPi as described here



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