Voltage display (V)Current display (A)Voltage adjustment (CV)Current limit adjustment (CC)On / off switchOutput terminals (+ red, − black) · green: chassis ground

V and A displays on the front panel, voltage and current knobs, red, black and green terminals
Benchtop box; displays, knobs and terminals on the front panel

Power supply

Lab power supply

In simple terms

What is this?

An adjustable water tap that gives the voltage you want; you set the pressure.

What is it for?

Powers the circuit safely; thanks to the current limit, parts do not burn if there is a fault.

Where do you see it?

In repair shops and school labs; the adjustable big brother of a phone charger.

How do you spot it?

A bench box with a display, buttons and red and black output sockets on the front.

Caution:

Set the voltage and the current limit first, then connect; do not touch the positive and negative outputs together.

Technical definition

A bench power supply where you can set the output voltage and the current limit. Thanks to the current limit, it restricts the current in a short circuit or wrong connection and protects the parts. Its display shows the instantaneous voltage and current.

Voltage0–30 V

Current0–3 A / 0–5 A

ModeCV · CC

Schematic symbol IEC and ANSI differ

IEC 60617: the drawing style used in Türkiye and Europe.

Pins 3

1Positive output (+)Red connection terminal+

2Minus output (−)Black connection end; the circuit's GND−

3Chassis groundGreen terminal; not connected to the output, the output floatsPE

Features typical

Voltage range: 0–30 V (adjustable)
Current limit: 0–3 A or 0–5 A
CV mode: Keeps the voltage constant
CC mode: Holds the current constant once the limit is reached
Output: Floating (not connected to chassis ground)
Warning: Runs on mains; don't open it, mains is out of scope
Example part: 30 V 5 A single-channel adjustable supply

Common mistakes

Leaving the current limit offWhen powering a new circuit for the first time, set the current limit low (50–100 mA). If there is a fault, the CC light comes on and parts don't burn.

Adjusting after connectingFirst turn the output off, set the voltage and current limit, then connect the circuit. A knob turned the wrong way can damage parts.

Connecting the polarity backwardsRed is positive, black is negative. Polarized parts (electrolytics, ICs) are damaged when powered backwards.

Test with a multimeter

Test whether this part is good with the multimeter on the measurement screen.

Take a measurement

Where it is used

Powering breadboard experimentsTracing current to find faultsSimulating a battery voltageMotor and LED test