Tip 120 as power transistor

A transistor is a semiconductor which is a fundamental component in almost all electronic devices. Transistors have many uses including switching, voltage or current regulation and amplification. Transistor controls a large electric output signal with changes to a small input signal. Since a large amount of current can be controlled by a small amount of current, a transistor acts as an amplifier. Transistor also acts as switch which can open and close many times per second.

The TIP120 also known as Darlington transistor. It was designed as a medium power switching transistor and can be used to switch a motor on and off. This type of transistor can use a small current to switch and amplify a much larger current to the motor or other load such as buzzer. The controlling pin on the transistor or base is sensitive to too much current, so the circuit required a 1k Ω or 2.2kΩ resistor coming from the output pin into TIP120. This transistor coupled with a motor power supply and will allow the circuit to run a DC motor and empower the circuit to activate many other devices. Therefore, for this project i used a TIP120 because it can pass more current especially if i add a heat sink on the transistor and handle larger load.

Troubleshooting the PCB line

After done with etching procedure, a PCB line should be check by using a multi-meter. This is important to ensure each component that will be install on the circuit board able receive a voltage and current and operate perfectly. Basically before soaking the copper board into the hydrochloric acid, the printed PCB line sometimes are not connected or dotted line. This problem can be fixing by drawing back those dotted line with a black marker pen and then continue soak the copper board into the acid.

Below picture shown the dotted line on the copper board

Making a connection troubleshooting using multi-meter.

Thus, the complete etching board will be drill to make a hole for electronic component placement.

Etch a single sided PCB

Etching is a printmaking process and where the excess copper is removed to leave the individual tracks on the circuit board. A muriatic or hydrochloric acid is important because it is used to remove the cooper layout on the circuit board.

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Etch a single sided PCB

Etching is a printmaking process and where the excess copper is removed to leave the individual tracks on the circuit board. A muriatic or hydrochloric acid is important because it is used to remove the cooper layout on the circuit board.

The copper board can be cut into a necessary size needed and then clean it using a paper towel from any dust. Make sure our hands clean from any oil before touching the circuit board. Then place the pcb layout on a copper board and stick it using a masking tape.

Thus, get ready with a clothes iron and set the iron on the hottest setting to allow the iron get hot. Before start ironing the circuit board, use a thick clothes such as kain pelekat to sandwiching the copper board.

Firmly press the iron onto the back of the PCB layout for about 20 seconds and repeat the same method for more than 5 minutes. Without moving the iron, press board very hard for 1 minute to provide perfect heat to the circuit board. Then slowly move the iron around the copper board with a lot of pressure. After done with these methods, make sure the circuit board fully cool before removing the PCB layout from the copper board. 

Pour some hydrochloric acid on a plastic container and soak in the copper board into the acid. Wait for 4 minutes and shake the container slowly to remove the copper layout from the board.  The copper layout can be easily separate from the board by this method. Repeat the same method for 3 or 4 times to get a fully circuit board.

Separates the circuit board from the acid and leave it for 2 minutes. Wash the circuit board using clean water and brush the copper layout side using a sand paper. Repeat the same method until the copper layout completely removed.

Printed circuit board layout

PCB (Printed circuit board)

Printed circuit board is primarily an insulating material used as base, into which conductive strips are printed. The base material is generally fibreglass, and the conductive connections are generally copper and are made through an etching process.  The main PCB board is called the motherboard; the smaller attachment PCB boards are called daughter boards or daughter cards.

PCB board design defines the electrical pathways between components. It is derived from a schematic representation of the circuit. When it is derived, or imported from a schematic design, it translates the schematic symbols and libraries into physical components and connections

PCB layout

The PCB layout is a mirrored positive one- black on white. The PCB layout is printed 1:1 on paper by using a laser printer or copier machine. The laser printer or copier toner will not run out when it gets wet or oily. Therefore by using a laser printer the output will be fine and form in high quality of printing. It might be possible that the toner texture on the layout prints from the laser printer is not dense enough and passes too much light. However, results might be improved by setting the toner density.