## Introduction: BENCH POWER SUPPLY UNIT FROM SCRATCH

In this instructable I am going to show you how to make a bench power supply. The bench power supply would consist of 6 fixed voltages and a variable voltage from 7v to 1v

## Step 1: What Is a Bench Power Supply and Why Do I Need It ?

A bench power supply is a very important and useful tool in electronics. You may not understand the importance of it until you make one or use one. The same was my case as I found it useless until I made one and millions of new possibilities opened up.

Basically a bench power supply is a tool through which you can get multiple voltages. So the bench power supply that we will make today will have 12v,10v,9v,8v,6v,5v and a variable supply ranging from 7v to 1v.

## Step 2: MATERIALS REQUIRED

A wide range of materials would be required for making this project and you should spread the work in one day to get better results.
So without further ado the materials are
•Enclosure for the projects
• Power supply(as I didn't want to do AC to DC conversation I simply used a 12v wall vort)

•7805
•7806
•7808
•7809
•7810
•LM 317
• 5k ohm pot
• 220 ohm resistor
• 0.1uf cap
• 1 uf cap
• banana clips male
• banana clips female
• switch

•voltmeter( buy voltmeter from ebay )

The tools required for the build are
• Soldering iron
•Solder
•Dremel or cutting tool
• A day or 2
you can get all the materials in about 5\$ to 10\$ depending on the place you live in.

## Step 3: MAKING THE LM317 VARIABLE VOLTAGE REGULATOR

You can follow the schematics given above and make the circuit . If you are not well versed with reading schematics check this out reading schematics

After you have the circuit on the purf board you can test it with a multimeter. DO NOT TEST IT WITH THE VOLTMETER as the max voltage on the voltmeter is 9 v and u will have tho test it through the 7808 the 8v regulator.

We will be doing the same in the power supply as to get 7 volts max.

## Step 4: MAKING THE OTHER FIXED VOLTAGE OUTPUTS

For making the fixed voltage outputs, solder all the voltage regulators directly on the board without putting them through as the thickness of the pins is very large. then give the 12v to the input pin and ground to the ground to all the voltage regulators. I put the 7808 or the 8v regulator directly into the LM317 circuit.

The outputs of these regulator would be used later to connect them to the banana clips.

## Step 5: PREPARING THE ENCLOSURE

For preparing the enclosure first put white tape all over the enclosure. then make the required markings and cut them using the dremel or the cutting tool. You may have to use the sanding tip also to clean the edges and give a good fit.

the enclosure is the major part and should be done with the most carefulness.

The holes for the banana clips can be drilled with the appropriate drill bit and can be screwed on well. Don't apply force on the plastic as it may break as it is very brittle.

## Step 6: WIRING IN THE ENCLOSURE

After the banana clips are fixed in the enclosure put in the 2 pcbs and wire the connections. The first clip is the variable clip and then followed by 12v,10,9v,8v,6v and 5v.

The voltmeter has three wires - one white,one red and one black. The black one is for the ground the,red is for the vcc or the positive terminal which can directly be connected to the 12v from the adapter. The white line goes to the output of the LM317 circuit.

A black banana clip is connected to the ground.

## Step 7: CLOSING THE ENCLOSURE

The last step is to close the enclosure. If you have access to a multimeter then test all the connections before switching on and also check the output from each clip.

Isolate all the electronics and put the screws in the holes and close the box.