0-12V 2A power supply

Posted on Apr 4, 2012

This project has two options. It can be a mains operated project, using a 2155 or 2156 transformer or it can be connected to a plug pack. We recommend it be connected to a 16v AC 1 amp plug pack as these are double insulated and provide complete safety for the constructor. As we have mentioned in the introduction, the 2 amp transformer M 2156 will not provide much more than 1.4 amps DC output so the 1.5 amp AC plug pack has nearly the same rating. By the time you buy a M 2156 transformer and power cord, the total will be the same as the cost of the plug pack so it should be one of your considerations.

0-12V 2A power supply
Click here to download the full size of the above Circuit.

The heatsink is one of the most important components in a power supply. It must provide adequate heat dissipation to protect a heat-sensitive device, from being damaged. All power supplies dissipate heat. Some are more efficient than others but whenever voltage and current are present together, heat will need to be dissipated. The way to select the correct-size heatsink is to build the project and fit a heat sink about 4cm x 10cm as a trial experiment. Next you need some high wattage resistors or car lamps to load the power supply to its maximum rating (this will depend on the transformer you use). Place one finger on the transistor and another on the heatsink, about 2cm from the transistor, and monitor the temperature rise in both positions. The heatsink in our project fits between the metal side of the transistor and PC board to get direct contact with the transistor. It is most important to get good thermal contact so that any heat generated in the transistor will be carried away by the heatsink.

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