# Make a 3.3 V & 5v Power Supply @ 1.5 Amp.

10,213

169

3

There's a lot of types of power supplies in the internet, but when we need to connect especial circuits that consumes a lot of current, it becomes very useful to use a good and efficient power supply.

A simple 78XX linear regulator can support without discipator for a normal consume, but if you wanna try to use more current this proyect can help you.This instructable will help you to make a power supply of 5 V & 3.3V @ 1.5 Amperes (With heat sink).

IMPORTANT:

Is very important that you should to use a 2-3 Amperes Transformer at leats for "supply" the current that tha "charge" requiers.

D1 IS CONNECTED TO THE REGULATOR FOR TO COMPENSATE THE LITTLE MORE ELEVATED VOLTAGE OUTPUT FOR THE B-E DIODE UNION. AND TO MAINTAIN THE 5.00 V REGULATED

IF YOU TRY THE CURRENT THAT IT CAN OBTAIN US THE OHMS LAW V=R*I

I=V/R IF WE HAVE 1 AMP THE VOLTAJE IS 5 VOLST WE USE A RESISTANCE OF 5 OHMS
A 5 WATS AT LEATS FOR THE PROBE.

P=V*I =5(1.5)= 7.5 W

AT THE MAXIMUN WORK THE VOLTAJE DECREASES 0.2 V BUT IS STILL USABLE. THIS INFO IF FOR THE IC 7805 AND LT1117.

## Step 2: Theory of Operation and Part List.

I use the TIP41 transistor. In principle, it can Supply Current about 2A (Says it's Datasheet
high enough to use. I like this number because it’s cheap, efficient, reasonable.

Most of 1,2,3,4,5 A use PNP Transistor (unpopular) and sometimes more expensive that NPN ones.

The transistor configuration is a common base that's say the theory os circuits a transistor thtat is used in this configuration Base to GND EMITTER AND COLLECTOR as input and output the gain is in CURRENT

Let's see a bit of theory:

in electronics, a common base (also known as grounded-base) amplifier is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a current buffer or voltage amplifier.
In this circuit the emitter terminal of the transistor serves as the input, the collector the output, and the base is connected to ground, or "common", hence its name. The analogous field-effect transistor circuit is the common gate amplifier.

As current is sunk from the emitter this provides potential difference so causing the transistor to conduct. The current conducted via the collector is proportional to the voltage across the base-emitter junction, accounting for the bias, as with other configurations.[1]
Therefore, if no current is sunk at the emitter the transistor does not conduct.

-Wikipedia

The 3.3 Volts Voltage Regulator

There are various kinds of 3v3 regulators, mostly used in SMD, I choose the Trought-Hole T0-220 Package

is and LM1117 3V3 RE Linear Technologies

Component list of 12v to 5v voltage regulator
IC1___LM7805___5V dc regulator IC

Q1___ TIP41____2A 50V NPN power transistor

C1____1000uF 35V___Electrolytic Capacitor

C3____100uF 25V_______”________”____

C2____0.1uF 50V___Ceramic or mylar capacitors

C4____0.01uF 50V____”____________”_______

D1____1N4007______1A 1000V

Diode LED1____LED any color as you like

R1____820 ohms 0.25W

## Step 3: Real Measures.

When you connect the power suplply and ready to work you can probe the maximun power that it can to deliver in a circuit before you connect it to the supply

Use simple Ohm's Law

V=R*I

Imax=1500 mA = 1.5 A and the output voltage is aprox. 5.01 volts the resistance you need is
R=V/I = 5/1.5 = 3.333 Ohms and the commecial value is aproc 3.3 Ohms

And the Power of the resistor is Pmax=V*I = 5.01*1.5= 7.5 Watts but you can put a 5w resistor for the probes only.
And the same with the 3.3 volts regulator:

Imax=1500 mA = 1.5 A and the output voltage is aprox. 3.28 volts, the resistance you need is
R=V/I = 3.28/1.5 = 2.18 Ohms and the commecial value is aprox 2.2 Ohms

And the Power of the resistor is Pmax=V*I = 3*1.5= 4.5 Watts but you can put a 5w resistor for the probes only.

## Step 4: The Files... Ready to Print and Make Your Own C:

Here the files of the artwork and if you wanna try the silk screen artwork the file is included too.

I taken a bit of pictures of the Copper Plate before it was made, check it out :)

## Step 5: Final Circuit Without Enclosure

Here the functional and final circuit.

I know the important of and enclosure, but i have to do more things and about the time, i don't hace too much, but you can modify,decorate as you want, please send me pics for to motivate me to make more instructables.

-Your favs and views feed my heart :)

## Recommendations

• ### Large Motors Class

12,809 Enrolled

## 3 Discussions

I see you did something that I always build into every power supply I build. And that is a LED indicator on the output voltage instead of a simple pilot lamp on the input before the transformer. And here is why I, and seems you too, did that. If you ever have a problem and wondering if you power supply is functioning correctly, the LED on the outputs of each supply voltage tells you it is working. I design that into every supply system I design for just that reason. I also built bench top power supplies with two selectable outputs and one variable output in the same construction box. That way I can use two separate supplies at the same time. And the fact that one is variable allows me to use it however I want as well. You've built a nice workable project. Thumbs Up!

get a transformer of 9v at O/P, 12 V is waste of power

You should try to find a transformer that puts out lower voltage, like 6v only, instead of 12.

At 12 volts your regulator needs to get rid of more than half of it, making it very inefficient and also generate unnecessary heat.