0-50v variable power supply circuit, at 3A

This regulator is 0-50v variable power supply circuit that adjust output voltage wide rage between 0V to 50 volts, and Also important is the overcurrent protection circuit at 3 Ampere. Which will immediately cut. The voltage regulation circuit because use IC-LM723 ICs will provide better performance. So is suitable as a power supply circuits for various experiments.

Since we ever present a project of this nature many more circuits. For example:
Cheap adjustable 0-30V 2A Laboratory DC Power Supply
Regulator 0-30V 5A by IC 723 & 2N3055 -2part
High power supply regulater 0-30V 20A by LM338
Bench variable power supply 0-30V
Variable Regulator 0-30V 5A by LM723,CA3140,2N3055

But them was old over for 20 years ago. Now we have a project that can be used to cover almost all applications. Because it can adjust voltage between 0V to 50V and we use 2SC5200 transistor replace the 2N3055 old transistor (Though very ancient, relays still have many uses.) And also apply current to 3A which better than DC voltage adjustable power supply 0-50V up to 2A by ua723-2N3055. Hope you’ll like it.

Technical information
Used the transformer size 24-18-CT-18-24volts at 3-4A
Has an overcurrent protection to prevent damage to the circuit.
Adjustable between 0-50 VDC (Depending upon the supply voltage used at AC IN point)
Can apply maximum current to 3A

The working of circuit
As Figure 1 is the project’s circuit diagram. The AC-voltage from the transformer will flow through diode D1-D4 to rectifier to DC voltage by has C1 act as filter voltage to smooth before sent through R1, R2 into TR5. And there IC1 is used to control a voltage at OUT point by adjusting VR1 can adjust voltage between 0-50 volts.

The circuit diagram of 0-50V 3A Variable DC power supply
Figure 1 The circuit diagram of 0-50V 3A Variable DC power supply

The R1, R2 will functions for limitting overcurrent by works together with TR1, TR2. When the current exceeded TR1 and TR2 will work, and will have output voltage out of E lead of TR2 through LED1 into 2 pin of IC1. So cause the circuit stop provide voltage. The switch-SW1 will functions in reset system to restart working of circuit again.

How to builds
This project have quite many components. You should experience a modest electronic.I am sorry for this project not have a PCB layout. But you can use the perforated PCB. As components layouts in Figure 2
The components layout and wiring
Figure 2 The components layout and wiring


New PCB layout for you:
Actual-size of Single-sided Copper PCB layout

And component layouts.

Mounting transistor to heatsink.
This project we use the 2SC5200 transistor to the heatsink as Figure 3 since when too much current load 2SC5200 it too heat. So must mount the large size heatsink. As Figure Proper way of mounting the transistor in a heatsink. Using hex nut and metal screw to mount them together by use mica insulator to protect short circuit.
The mounting the transistor on the heatsink
Figure 3 The mounting the transistor on the heatsink.

Connecting the transformer.
If you want to use output voltage are 0-50VDC can connect 18,24 terminal. The output 0-30VDC can connect 0,24 terminal and The output 0-20VDC can connect 0,18 terminal.
connecting wrong polarity voltage is low
Figure 4 connecting wrong polarity voltage is low

But I cannot buy the transformer as Figure 4 so use 2 transformers to connected with 0-18V and 0-24V in series. If you connected the wires is 5VAC as Figure 4. It means that, you connect the transformer wrong. Must return a new polarity wire. We will read voltage about 43V.
Eventually we will have a successful circuit of Figure 5.
Figure 5

Connect the transformer as shown in Figure 2 by a coil of a transformer to match our needs. Then measure the voltage at OUT. Supply power to transformer to observe that the meter, will need to measure the voltage from 0-50V by adjusting the VR1.
As Video below.

The repairing
As the circuit is a device that is not much. So in most cases Why the PCB is often caused by wearing the wrong device position and soldering. When the circuit is not working, might be the position. Make sure that all the various solder points.


The components list
1. LM723_____High precision voltage regulator = 1 pcs.
2. TR1_______BF423____PNP transistor_________= 1 pcs.
3. TR2,TR3___BF422____NPN transistor_________= 2 pcs.
4. TR4_______BD140____PNP transistors________ = 1 pcs.
5. TR5_______2SC5200__NPN transistors________= 1 pcs.
ZD1__________36V 0.5W Zener diode___________ = 1 pcs.
D1-D4________1N5401____3A 100V Diode______ = 4 pcs.
LED1,LED2____LED 3 mm as you want__________ = 2 pcs.

R1,R2_______0.1 ohms 2W____________________= 2 pcs.
R3__________56 ohms 0.5W___________________= 1 pcs.
R4,R10__________100K 0.25W ____________________ = 2 pcs.
R5,R8,R20_______10K 0.25W____________________ = 3 pcs.
R6,R22,R23______1K 0.25W______________________= 3 pcs.
R7__________15K 0.25W_____________________ = 1 pcs.
R9__________2.7K 0.25W____________________ = 1 pcs.
R11,R12______5.6K 0.5W____________________ = 2 pcs.
R13,R17_______8.2K 0.5W_____________________= 2 pcs.
R14,R15,R16__10K 0.5W_____________________ = 3 pcs.
R19__________330 ohms_____________________ = 1 pcs.
VR1_________10K potentiometer_______________ = 1 pcs.
Ceramic capacitors
C6_______470pF 50V________________________ = 1pcs.
Mylar Capacitors
C2,C7_____0.1uF 100V________________________ = 2 pcs.
Electrolytic capacitor
C1________2200uF 63V__________________________ = 1 pcs.
C3________47uF 50V__________________________ = 1 pcs.
C4,C5_____10uF 50V__________________________ = 2 pcs.
C8_______100uF 63V___________________________ = 1 pcs.
SW1_____Reset switch normally open pushbutton______ = 1 pcs.
PCB,wires,heatsink,nut,screw,and other.

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