Re-purpose your old mobile phone chargers into a triple output power supply for bread-boarding analog and digital circuits.
Mobile phone chargers which connect to the utility wall outlet are efficient switch-mode-power-supplies which convert the utility 110V/220V AC supply to 5V/6V DC with current ratings from 250mA to 1A and provide isolation from the AC mails.
Five chargers when suitably connected can form an excellent triple output power supply for bread-boarding analog and digital circuits.
Input AC 110V-240V 50/60Hz
Output 1 +5V DC 500mA Suitable for Digital IC's
Output 2 +12V DC 250mA Suitable for Analog IC's
Output 3 -12V DC 250mA Suitable for Analog IC's
The images show a demonstration of the power supply when used to power a typical analog/digital circuit being tested at bread-board level.
A LM555 timer IC is operated at +5V and forms the clock for a 74193 4-Bit binary counter. The counter outputs are fed to the 4 msb's of a DAC 0800 whose voltage reference is provided by a 9V regulator chip. The DAC output is fed to a LM741 OP Amp. The DAC and OP Amp operate with +/-12V
The Oscilloscope display shows the 4 counter outputs and the overall DAC output. https://www.instructables.com/id/DIY-USB-OSCILLOSCOPE-IN-A-MATCHBOX/ is used to capture the waveforms.
Caution: Mobile phone chargers operate at the mains voltage of 110V/ 220V and extreme care must be taken while building this unit.
Five mobile chargers are required. One of these must be a true 5V output unit suitable for digital circuits which have a strict supply voltage range.The other four could have a nominal voltage of 6V. These would be paired and used for the +/-12V output. Analog circuits typically accept a large supply voltage range and the nominal 12V could vary between 10-12V. Any voltage references would need to be separately derived from these voltages.
A plastic pencil box is suitable for this power supply as it would be well insulated from the mains voltage contained within the overall unit.
It is necessary to do a quick check to see that the five smps modules removed from the mobile charges fit comfortably within the box. Space must be catered for the switches connectors and wiring.
A mains patch cord, DPDT switch, output terminals and legs for the box are required.
Electrical tools, soldering iron and wires are essential to complete the wiring and assembly.