Digital multimeter power supply circuit diagram with MP3 charger

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The digital multimeter has high measurement accuracy and intuitive reading. Deeply loved by electronics practitioners. Now I will introduce the MP3 charger, which can be used as a digital multimeter power supply after a simple boost circuit.

The +5v voltage output from the MP3 charger is connected to the boost circuit through the USB interface (as shown in the drawing). In the figure, IC1 is a CMOS integrated block, model: CD40lD6. It consists of six Schmitt triggers internally. One of them is connected to an oscillator, and the remaining five are all connected in parallel with their input and output terminals as an oscillation pulse output stage. D1, D2, C2, C3 form a voltage doubler rectifier circuit, and the rectified output voltage is about +9V.

This circuit uses a small number of components, you can find a "snake board" that is slightly smaller than the 9V laminated battery.
Laminated. The CMOS integrated block used on the circuit, when conditions permit, is best equipped with an integrated block socket, no special requirements for other components.

Determine the Rl, CI value of the oscillation frequency, a slight deviation is not a problem, as long as the installation is correct. It is not necessary to debug the position of the digital multimeter 9V battery, and the digital multimeter power supply positive and negative lead wires can be connected to the voltage doubler rectifier output terminal to work.

The MP3 charger is easy to set up with a switching power supply. It is energy-saving and compact. It basically has a USB port. It is an ideal low power AC/DC converter. Although the output current of the above circuit is not large, it is still possible to supply a digital multimeter (after a long period of use). I believe that friends who work in electronic work with digital multimeters, on the above circuits. You can "get it" in hours. From then on, completely solve the problems of worrying about the amount of battery remaining, buying batteries, changing batteries, and so on.