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I am writing this Instructable because I´ve got a lot of questions about my little USB-powersupply for my breadboard and a lot of request to write an instructable about it. I needed a new one anyway because my old one died because of a cat with sharp teeth.

I think that it is safe to say that most of the people who make (big or small) electronics-projects have a pc or laptop in theire hobbycorner and a lot of projects need 5V for IC's or microcontrollers. So using power from a USB cable isn't that farfetched and lets face it: a lot of devices around us use a USB-connection to get their power or to charge their batteries.

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## Step 1: About USB-connectors and -power

For this Instructable you can use any USB-connector you like (or you can even cut the cable and solder the wires) but I will use a B-type. The pins always have the same function for all types of connectors.

Pin#Color CableFunction
1RedVcc (5V)
2WhiteData-
3GreenData+
4BlackGround

Voltage = 5V
max Current = 500mA

## Step 2: What Do You Need?

In this Instructable we will make a very simple power supply with only the USB-connector and a power-on led. But you can add whatever you fancy such as a power on/off switch or or a regulator to get 3,3V (fused or not) or........

So for this Instructable we need:
• USB B connector
• An LED
• A 150Ohm resistor
• Something to hold the lot together
• soldering iron and solder
Please be careful when soldering. Children should always work under adult supervision!

## Step 3: Leds Get Our Hands Dirty

Soldering everything together is actually very easy.

• Connect the led with pin1 (Vcc) of the USB-connector and then connect it to pin4 (ground)  with the resistor inbetween.
• Connect pin 1 with one pin of the headerpins and pin 4 with the other.
• I soldered another pair of pins to the board but they are not connected. They just give some extra stability when connected to the breadboard.

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## 16 Discussions

I made it but slightly differently. Since breadboard power lines breaks in the middle I've decided to made it with double headerpins and the usb in the middle so to put it in the middle to power both lines at the same moment. Also I've added a couple of female headers to allow eventually to jump directly from the power source to the breadboard but also to be able to give power source from other than USB, like an external power supply. It is very useful, thanks for the idea

hey i have a power bank used to charge mobiles, can i use it with this setup for a micro controller project?

Just a note to let you know I have added this ( a year ago ) to the instructable:

Comprehensive Guide to Electronic Breadboards: A Meta Instructable

Take a look at a bunch of project involving breadboards.

Nice this was very easy to make instead of the other complex ones. I feel like this would work for people who are kinda of in a rush and is looking for good quality.
Now if i was to add a 8 pin push switch it would be between the resistor and the Led right?

Unfortunately with this design you don't have access to 500mA. You only have 100mA maximum. The USB specification will supply 100mA to anything on the bus, but it's designed to only supply its maximum 500mA once the hardware in the device has introduced itself and sent a higher power request. Without using a USB controller/interface chip in the power supply circuit you're limited to 100mA.

There are rumours of Apple building high-power USB ports into their newest computers that will supply between 1 and 2 amps. That's so you can speed-charge an iPhone4 or an iPad without using a mains charger.

2 replies

Just an idea, could you not run your breadboard from 4 X 1.2 volt nicads, and then charge the nicads via a schottky diode? i quickly hooked up such an arrangement, and measured between 13 an 19ma charge.

This would give you the instant current when demanded and still be trickle charging at the same time.

Saying that, i have a 4 X AA cell nicad charger, and looking inside that, all 4 cells are connected directly to the 5v USB bus!

You are 100% right. I forgot toput it tat way in the instructable indeed.

I made this quickly to do some testing while using the 5V from my laptop. I did not need more than 100mA and it still works fine for most of the smaller projects I do. For all the rest of the testing I use a regular power supply.

I'm using a resettable fuse in mine. here it is: http://www.sparkfun.com/commerce/product_info.php?products_id=8357