## Introduction: Adjustable Constant Current Source 4mA to 3A

Hello, in this project i want to show you aadjustable constand current source, wich maximal current is 3A by 39V. This is a very usefull circuit, to light up power LEDs or heater, also it is a very cheap and tiny circuit, which is easy to build. For the project you need basic soldering skills and basic elektronic skills.

Features:

Current range: 4mA to 3A
Voltage range: 1,2V to 35V
Temperature range: +-0°C to +125°C
Size: 4cm x 3cm x 5cm
Costs: 1\$ to 5\$

## Step 1: Part List

Parts:

LM350 (or Equal)
Heatsink for the LM350
Terminals
circuit board
Potentiometer 15OHM  1W, 2W or 5W
Wire
Unisolatet wire

Tools:

Soldering coil
Solder
Screwdriver

Other:

power Supply
maybe a 10W LED or a 5W 2,7OHM Resistor for testing
a multimeter

## Step 2: Circuit

The circuid is veeery simple, you only have to wire 2 electronic components and  2 terminals. be carefull with the LM350, dont confuse the pins!

## Step 3: Assembling

Now assemble it, make sure that you got thick wire for the circuit board and the potentiometer because there can be currents about 3A. Also make sure that everything is good soldered and the heatsink is good connected to the lm350! also dont forget to mark the terminals with "+ - input and output"

## Step 4: Testing (yay :D)

For testing you need a power supply (i prefer for that 12V), a multimeter, a resistor 2,7OHM 5W (!!!), and wires.

now connect the positive output of the constant current circuit to the 2,7OHm 5W Resistor, switch your multimeter to ampere measurement and connect the positive probe to the other side of the resistor.

Next connect the negative probe to the negative output of the constant current circuit.

!!! DONT short circuit parts of the circuit and DONT short circuit it with your FINGERS!!!

Regulations the potentiometer to the middle position!!!

now connect the power supply to the input of the circuit, turn it on and regulate it to 12V.

If you twist the potentiometer the multimeter should show the floating current, which should be from 0mA to 1,3A - SUCESS!

But why 1,3A i told it could reach 3A... it can you just have to regulate up the voltage, then the current should rise.

The output Voltage should be 0,7V lesser the the Input voltage.

## Step 5: Final Step!

Troubleshooting:

errors could be:

confused the pins of the LM350
short circuits
electronic components burned out

Uses:

Heaters
High current LEDs
current limit