The power supply provides a stable regulated bipolar voltage in the range ±1.5V to ±17V. It is based on LM317/LM337 linear voltage regulators that also have a short circuit protection. Most parts are purchased from Radioshack, including a 6"x3"x2" project box, 12V 1.2A center tap transformer, pots, knobs, etc.
| Schematic | Transformer | PS box | ||
The schematic is just a standard application of LM317/LM337. The circuit is assembled on 2 perfboards. One of them takes the transformer and 1A fuse (left image). The other one accommodates two electrolytic caps (2200μF), ICs on heat sinks, and other discreet components (right photo). The heat sinks (available at Radioshack) allow to put #4-40 threads in their roundish holes, which is used to mount the heat sinks on the perfboard with two #4-40 bolts each.
| First board | Second board | |
The pots are mounted directly on the box top surface. Their shafts were shortened to match the height of knobs. The 10μF electrolytic caps are soldered directly to the output posts. Due to the box rails, the entire design is mechanically stable. The right image is an overall view after mounting the bottom cover.
| Inner view | Outer view | |
Because of a small transformer and heat sinks this power supply is not intended to provide a high output current. The circuits involved into the PIC experiments rarely consume more than 500mA including the control devices like small motors. Such current can be safely taken/sinked by this power supply without an overheating. The maximum current the IC can handle is 1.5A and one can also use this supply for about 1 - 1.2A currents too, but for a reasonable short time to prevent the overheating. Generally, the higher is the output voltage, the higher current can be consumed safely. However, one should avoid using the power supply for voltages below 5V and high currents (above 0.5A).
Last modified:Mon, Jan 23, 2023.