In our laboratory, we often need to power several devices that require different power supply voltages for occasional use. The idea behind this project is to have a power supply to feed them all, but without a rotary selector to configure the voltage. Instead, the connector-programmed PSU is using a preselection system for different voltages, generated with fixed resistances, and connected to different pins of one connector. In this way it is possible to set up different connection cables, each with its own preset voltage, by using different pins of that connector. In fact, each of our devices to be powered will be equipped with a properly wired 7-pin DIN connector. Because one sort of connection cable belongs to one voltage, we will never take the risk of causing damage from overvoltage.

Circuit

The power supply shown in Figure 1 has a classic linear configuration, with a mains transformer T1, a full-bridge rectifier BR1 followed by an initial high-capacity filtering stage with C...