# 8 How to convert 12V to 6V step down circuit

Your load is too hot. It will be damaged. Why? You connect it to a 12V battery. It can get 6V only. If you do not want this to you. You should read 10 ways to make 12v to 6v step down circuit.

I try to show you many ways to do. You can choose the best for you. For example, you have these parts, or it is easy, or cheap. You can build them as you need.

## 1. Limiting current resistor

If you use a load that uses constant current. For example, LED, Light bulbs, relay coil, and more.

You can use a resistor in series with these loads. This way is cheapest and so easy.

Suppose you have 6V 3W light bulbs. You can use a resistor.

### How to find resistor level

First, find the current of the light bulbs or R1.
I = P/V
P = 3W , V =6V
So, IR1 = 3W / 6V = 0.5A

Then, Find voltage is across R1 (VR1).
Look at in the circuit, VR1 = VB- VL
VB = 12V, VL = 6V
So VR1 = 12V – 6V =

VR1 = 6V

From the theory: R1 = VR1 / IR1
So, R1 = 6V / 0.5A = 12 ohms.

Next, we need to find the power of resistor-R1.

PR1 = VR1 x IR1 = 6 x 0.5 = 3W

So, You should Resistor size is 3W.

Also, you can use a 6V relay to 12V by helping of a resistor.

### Too hot and big

We will see that if used a too high current of the load. We need to use high watts of a resistor. It is so a large size and also too hot.

## 2. Load using unstable and low currents

We should choose the circuit to be suitable for the load. If you load use unstable currents. And low current using.

For example, you have a portable FM radio. Of course, you cannot use it to the car directly.

It requires about 5V to 8V. And in different the level of sound. It uses a different current too.

Even it uses current just 0.1A only. But we can use a limiting current resistor as above.

Because it uses an unstable current.

### 2.1 Using Zener diode and transistor

Basic step I often use Zener diode and transistor as voltage regulators. Because it is easy and cheap. Look at the circuit below.
This gives 6.2V stable output voltage at 200mA.

How it works
First, 12V come into ZD1 and R1. They are a Reference voltage of this circuit, 6.8V. Then Q1 increase a current is higher to the output. The output is 6.2V because some voltage is across BE of Q1.

More current
If you use BD139 NPN transistor. It can drive current about not over 0.5A. You can change It is TIP41 for 1A output. And 2N3055 for 2A output.

The fixed 6V output
In normal if we want 6V output. We need to use the 6.6V Zener diode. But no it in the datasheet. There are only 6V, 6.2V and 6.8V.  We can do it with diode in series.  Look at the circuit below.

## 12V to 6V step down circuit using 7806

Normally, We always use a 3 pin DC voltage regulator(IC78XX series) for this job. Which may be will apply number 7806 provides the voltage of 6 volts.

This circuit can give 1A max current.

## Step down voltage to 6V using 7805

But it does not a popular number. In my stores have IC-7805 is popular IC is applied in many digital circuits (5 volts power supply).

However, we modify a 7805 to the output of 6 volts in easily. When we add a chain of a diode such as 1N4148, in series at between the common pin of IC1 and Ground. It will increases the output by +0.7V for every diode used.

In the circuit below. We add 2 diodes (0.7V + 0.7V). Therefore, the voltage of output is 1.4V + 5V = 6.4V.

This way is easy if you have diodes in your store.

And both capacitors are used for absorbs or smooth a fluctuating signal as shown in Figure 1.

### Building 12V to 6V converter

Since they use a few parts, so assemble them on perforated board or Universal PCB board. as Figure 2. We will see that the output voltage is voltage drop across both diodes (0.6V + 0.6V) puls with The IC voltage equals about 6.2 V approximately. (on digital multimeter shows 6.4 volts.)

The output current from the IC about 1-ampere max. It must be the heat sink to the IC with the current size. And Then we can increased output voltage in other sizes such as 8 volts so can use instead IC is number of LM7808, to add diodes into 4 pcs connected to IC-7805. again.

If this not working.
If IC1 is very hot please check pins and wiring again.
The output may be a short circuit.

If higher, please check IC1’s the ground pins and all diodes in series, the voltage across them should about 1.2V

## Use 7805 to set fixed 6V output with pontentiomer

Some need 6V constant voltage. It is easy to adjust with a potentiometer. Look at the circuit below. You can adjust voltage from 5V to 12V with VR1.

## 12V to 6V DC converter using LM317

If you want current 1.3A output. You cannot use 7806. But you can use LM317. It can give current more up to 1.5A. Look at the circuit below.

## 6V DC converter circuit at 3A using LM350

In the case of 2A to 3A load. We have many ways to do. But first, if you want to build easily. LM350 is best. It is similar LM317 but more current up to 3A max. Look at the circuit below.

### How to find R2

It is easy if R2 is a potentiometer. But how to find the resistance of R2.
We can find.

Vout = 1.25 x {1+(R2/R1)}

Vout = 6V, R1 = 270 ohms,

6V = 1.25[ 1+ (R2/270)]
6/1.25 = 1 + (R2/270)
4.8 – 1 = R2/270
R2 = 3.8 x 270 = 1026 ohms

So, we use R2 is 1K.

## 6V 2A to 5A output converter using 7806 – transistor

But sometimes you may not have LM350. You have 7806 and TIP42 (PNP transistor). Just like this, you can build an 6V 2A step-down converter. It is easy too.

## Also 12v to 6v step down circuit

We have many ways to reduce voltage down to 6V. All circuits below are 6V regulators.
You can apply it. With choosing 6V step only.

### Related Posts

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1. Clarkdale44

Hello

I tried this circuit for powering my led emergency light which runs on 6v. As i only have 12v batteryy. At first it worked for 5 minutes then transistor got very hot, i attached a big heatsink with 7805. After few minutes it just turns off. I tried testing voltages using MM. When my led is off it shows voltage of 7.5v(I connected 4 diode), but then as i turns on my lamp, voltage drops to 1.2v? What do u think might have happened?

2. Hi, Clarkdale44
Thanks for interesting question.

I need help! I want to take a 400-500watt computer PSU, use the 12v wire rated at 12-14 amps(there are 2 wires that are powered this way) and reduce it to between 6.8-8.4 volts with a max peak amperage draw of 20 amps. Please help, I found something from the golf cart work that can do this but I’d like to know how to do this so I can make it myself. Email me anytime day or night as this is a pivotal part of my prototype project

4. pandiarajan

i like it

5. MR OHM 1970

Another Great Project,,,I Love It!!!!!

6. IBRAHIM LAMOOD

greet for LM350 it work WITH PLASTIC NOT METALIC ONE

7. It would be nice if someone who wrote English a bit better would edit this. I thank the author, but your grammar is very difficult to follow. I appreciate the attempt!

• Hello Scott P,

First, thank you so much. You are very kind for telling me.

I am practicing English regularly. It is difficult and so great for me.

Now I am starting with reading English books for kids. I’m not sure, Is it the right way?

Many people say to keep short sentences. And use simple vocabulary. So grammar will be good, is it true?

If you are free. Please recommend me. How to improve my English in simple ways.

Thanks again.

Apichet

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