0-60V Dual Variable power supply circuit using LM317&LM337

If you want Dual Variable power supply circuit that covers most applications. This circuit may be what you’re looking for. The price you deny difficult. With the following features.
1. On signal, the mode can supply DC voltage between 0 volt and 60 volt
2. Can provide DC dual variable on positive, negative and ground are +/- 0-30 volts.
3. Can supply current out maximum about 1.5 A.
4. Use the most popular IC are LM317T and LM337 circuit, so do not have to worry about finding the device, and it certainly easy.

Before construction, we study the properties of important devices, is regulator IC.

Choosing Regulator IC
The regulator IC is used to regulates DC voltage, which in this circuit we use an IC number of LM317T for the positive voltage and the LM337 circuit for the negative voltage. Both IC have the same features. Thus, So describes specific number LM317T only.

0-60-volt-dc-variable-power-supply-using-lm317-lm337


Figure1: 0-60 volt DC variable power supply circuits using LM317&LM337

The LM317T is readymade regulator IC can use to adjust voltage from 1.25 volt to 37 volts, there is 3 leg, body same the regulated IC number 7805.

But it batter that can provide to 1.5 A and get input voltage from 3 volts to 40 volts It’s easy to applications and, of these features have advantages over the regular letters IC 78xx series a lot.

In addition, Internal the ICs has full protection, the short-circuit protection, input over the voltage protection, overload protection. And another interesting feature is the elimination the ripple.

The output voltage (Vo) Determined from the formula.
Vo =1.25{1+(R2/R1)}

The R1 is the resistance constant between 120-240 Ohm. We can adjust resistor-R2 from a minimum value (0 ohms) to the value as we want. If R2 is 0 ohms minimum output the voltage of about 1.25 volts.

Making LM317 start at 0 volts

In electronic circuits require constant voltage. Would not be necessary to make the voltage at the output of LM317T down to 0 volts. However, in the experiments will be necessary to adjust the voltage. The IC LM317T, there is a weakness in this is the output the voltage minimum adj pin is connected to ground is equal to 1.25 volts.

But there are tricks to make LM317T adjustable voltage output is 0 volts. By creating a lower reference voltage to 0 volts to 1.25V (-1.25 volt). Then to the adj Will be able to adjust the output the voltage to 0 volts.

The negative voltage regulated IC number LM337T as same is if adj pin connects to ground will get lowest output voltage into -1.25 volt. Which if adjust as 0 volts reference voltage of +1.25 volts, it must be connected to the adj pin of the IC only.

How the Dual Variable circuit works

In figure 1 is this complete circuit. The Diodes D1-D4 are rectifier ACV from 24 volts of the transformer is DCV of about 33 volts both positive and negative voltage. The capacitor C1 and C4 is voltage filter from the bridge diode to smooth. The R1, D5, and D6 are made the reference voltage of +1.25 volts to the LM337T to adjust to 0 volts.

The R3, D10, and D11 make voltage -1.25 volts to LM317T to it can adjust to 0 volts as well.

The D7, D8, and D12, D13 protects voltage backward voltage from the output. Which may make IC Which may cause damage to the IC.

The C2 and C5 are connected to reduce noise signal that from adjustable the potentiometer (VR1, VR2) and makes the voltage at the output to smooth up.

Judicially built and tested before applications
This project has a few amounts of equipment. We can assemble onto the versatile PCB. Check the circuit for error. When you are sure all the wires and components are installed correctly.

After examining successfully assemble the devices. Then, try to apply AC power. If not was wrong. Hold the DC voltmeter measure the positive output. And then Rotate VR1 you can read the voltage from 0-30 volt.

If everything is correct, then move the lead of the meter to measure the negative. And then adjust the VR2 can read voltage from 0-30 volts. Everything is ready for applications, However, if the malfunction, disconnect the transformer. Then find unusual.

Build Dual Variable power supply circuit

This project is not used many components so can assemble on the universal PCB board. But can make a Single-sided PCB layout as Figure 2. And see the wiring and various components layout can view the example in Figure 3. But be careful the polarity of the electrolytic capacitors and Diodes and both IC1-LM317, IC2-LM337 correctly and hold proper the heatsink.

pcb-layout-of-0-60-volt-dc-variable-power-supply-using-lm317lm0337
Figure 2 The Single-sided PCB layout

components-layout-of-0-60-volt-dc-variable-power-supply-using-lm317lm0337
Figure 3 The components layout of this projects

FAQ
The LM317T is positive voltage regulator ICs that low watts because are the plastic case or TO-220 model.
The LM317K is higher watts because of the metal case TO-3 model.
The LM337T is negative voltage regulator ICs in TO-220 model.

Also Dual variable power supply

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» Dual adjustable Power Supply using 7805 and 7905

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