Introduction: Small Breadboard Power Supply

Having a huge lab bench power supply on your desk can take up a lot of space. Sometimes you just need a stable low current 5-Volt power supply to test a simple breadboard project. This project shows how you can make a power supply that almost takes 0 space.

Step 1: What You Need

To make a power supply you will need the following:

Materials:

-Solder
-wood glue or other PVA based glue
-(black) spray paint
-toilet paper
-old newspaper or equivalent
-wire with jst female connector (for power supply)
-wire with jst male connector (for in breadboard or electronics project)
-heat shrink tubing
-a fresh 9-Volt battery
-a not so fresh 9-Volt battery

-low drop voltage regulator, i used LM2931AZ5 (check the datasheet)
-2 ceramic capacitors 100nF (check the datasheet)
-1 electrolytic capactitor at least 100uF, is used an old 470uF (check the datasheet)
-pin layout: since you're checking the datasheet anyway, make notes of the pin layout.
 

note: the datasheet of my regulator said the ESR value of the output capacitor is critical. From my personal experience, you need two 100nF capacitors and one electrolytic  capacitor, or else it will oscillate audible!


Tools:

-multimeter to test the circuit
-pliers to open the battery
-scissors
-soldering iron

optional: a breadboard circuit in need op juice.

Skills:

-handling a soldering iron
-patience


If you already have a 9-Volt battery clip, you can skip step 2.
If you don't want to paint the power supply, you can skip step 11.

Step 2: Getting a Free 9-Volt Battery Clip

Just use the pliers to remove the metal casing. The battery either has small individual cells in them or a stack of wet cells in a plastic container. Be carefull not to short or open the cells!
Mine had some paper near the clip. Just remove that.
Cut off the connector. By doing it the wrong way, like i did, you will temporarily short the battery. If the battery is dead flat then it probably won't hurt, but be carefull!
Dispose of the battery cells properly.

Step 3: Place the Components

Step 4: Solder Step 0

Solder the regulator and the ceremic capacitors on the input and output.
Pre-tube the wire.

Step 5: Solder Step 1

Solder the connector. This is the right time to check if the wires don't touch. The next step will be soldering the electrolytic capacitor. You don't want to start over again.

Step 6: Solder Step 2

Solder the electrolytic capacitor. Watch the polarity!

Step 7: Test the Output

Step 8: Shrink the Tube

Step 9: Apply First Layer of Toilet Paper

Cut out a little square of toilet paper. It should fit around the connector. You want a bit to stick out on the bottom. Apply some glue to the square and smear it out.
Apply the toiltet paper and gently press it.

Step 10: Apply Final Layer

Apply another layer. You have to be a bit quick here. You don't want the glue to start setting. Just fold the edges over.
Cut of some excess paper.
Carefully wipe the surface with your finger to make everything fit nice.
Clean up the mess and set the power supply away.

Step 11: Finishing Touches

When the glue is almost dry (you can let it set for a few hours or overnight), you can start spraying it.
Get some old newspaper and go to a well ventilated area.
Spray one or two layers of paint on your power supply.
Done.
Now you just need a electronics project to use it with...

Note that after a week or so the glue will be completely set.

Comments

author
ratgod (author)2011-09-11

I love the idea of toilet paper and wood glue, I've never thought of that before.

I have something similar but it's much bigger and it has a socket for the standard 9V wall supply connector. I'm too cheap to buy batteries ;)

I think I will build one of these though, excellent for building a portable lab.

author
janw (author)2011-01-04

Nice instructable. I did build a similar thinga long while ago but mine had a switch added so that it could switch between 5V and 9V. I must admit that I never use it anymore. most of the time I use power from a USB port to power my breadboard for lowcurrent 5V projects

author
critiacrof (author)janw2011-01-04

Thanks.
My usb port actually doesn't deliver the full 5 volts, plus I don't want to risk blowing my motherboard. So i rather use this one. The switch is a good idea!

author
janw (author)critiacrof2011-01-05

you could add a small quick fuse to avoid blowing your usbport

author
critiacrof (author)janw2011-01-05

Sure. But i rather use a bench power supply than a usb port: it can deliver more current and it has a more stable voltage.

b.t.w. this power supply works good on the arduino too: you will be able to drain energy more from your 9-Volt battery.

author
aelias36 (author)2010-12-30

Nice instructable! Question though, (i'm probably gonna sound like a complete idiot for asking this, but,) what's the point of all the capacitors? Wouldn't the regulator work just fine by itself?

author
critiacrof (author)aelias362011-01-04

The capacitors have multiple functions. One is to prevent oscillations. Another one is to absorb peak current. Digital circuits can have high peak currents.
And finally stabilisation. The regulator is not capable of instantaniously changing the amount of current it supplies to the output. Without a capacitor it wil respond too late to a dip in the voltage and possibly overshoot. The capacitor gives the regulator more time to respond to a lower voltage.

author
aelias36 (author)critiacrof2011-01-04

Oh, I never knew that. Thanks.

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