Portable 5V Regulator





Introduction: Portable 5V Regulator

About: I am Electronic Visualization Artist. I look at things through the Looking Glasses.

I made this 5V Portable Voltage regulator to be part of my Palm Arduino Kit.

I placed the circuit right on the 9V Battery holder with double sided foam tape.
The circuit was one side circuit.

I placed the components on the solder side of PCB board, because I wanted to use the component side of the PCB to stick to the foam tape and place it right on the top of the 9V battery holder.

The 5V Portable Voltage regulator consists of

Slide switch
1N4001 Diode
100uF Electrolytic capacitor
10uF Electrolytic capacitor
78L05 Voltage Regulator with TO-92 package
and 2-pin Female socket with hookup wire
PCB about 5/8" wide x 1" long.

The schematic of this 5V Voltage regulator is from my notebook when I started to learn embedded electronics.  As when I first learned why the diode was added. Because it blocks current from flowing in the opposite direction. And it will block current from flowing backward and damaging the system if you accidentally hook up the power supply the wrong direction.

To built this Portable 5V Regulator is quite easy.
Just solder the components according to the schematics.
And be careful about the polarity of the the diode, and capacitors.
For the 78L05 IC also need to be careful on the pins connectivity.

I used 2-pin female socket as the power connector.

NOTE: Thanks to bamfieldjames for an excellent question regarding the LED indicator. So I revised the schematic (as shown), by adding a LED indicator. The dotted connection near 5V output is an option if it is not feasible make a connection at the switch.

Electronics Tips and Tricks

First Prize in the
Electronics Tips and Tricks

3 People Made This Project!


  • Creative Misuse Contest

    Creative Misuse Contest
  • Clocks Contest

    Clocks Contest
  • Oil Contest

    Oil Contest

41 Discussions

I've been looking to build a very similar circuit, but didn't realise it could be made so small!

Is there any chance you could post a diagram of the circuit board, as it's hard to tell exactly how you've built it!

I was wondering how long one 9v battery powered your arduino on this setup. I am looking to do something very similar.

can you explain to me, why you used the capacitors. In my circuit analysis programm they don't make a difference. I still get 5V

1 reply

The capacitors are typically not needed if the input voltage is relatively stable (like from a battery), and if the load is not a greatly varying load. However, as a typical design practice, they are added to help smooth out the input and output voltages. For most of my projects, I don't use the capacitors, unless I truly see some issue with my circuit not working correctly. Since this project shows very short leads, there would not likely be any interference caused by outside electromagnetic fields. If the input or output wires are very long, then there is more chance they could be affected by nearby electrical or even changing magnetic fields (like a motor or other wires with higher current), they could act like antenna and pick up noise which would affect your output voltage.

Capacitors don't like to change their voltage very quickly, so if used, they will help reduce or eliminate any unwanted changes from these outside influences. The frequency and amount of voltage ripple reduction is determined by the values (Farads) of the capacitors, and depending on the resistance, you can calculate the RC time constant to understand how smooth the ripples can become. They also help to reduce any unwanted voltage spikes that may occur, depending on how complex the circuit actually is.

Hope that helps.


4 years ago


Thank you so much for this instructable. I went to my local electronic hardware store, picked up the components, even got a simple multimeter for 8€ and soldered everything together. My measurement was 5.00V, it worked great.

Thank you so much for your circuit diagram, never saw something so simple and well explaining. I just connected everything the way you drawed.

I will use this to power my Arduino Nano with a 9V battery.

Thanks for sharing.

1 reply

Thanks for the kind words!

It would be nice, if you could click the "I made it!" button! :)

And please check you PM mail box.

So I made this cool little device, and it charges my phone just fine. I used the same parts as described in the parts list, however, when I test it with my hobby multimeter from Radio Shack, it reads 4.95 volts. As I'm using this primarily to power up my usb stick for an usb otg (0n the go) cable for my phone, I think it needs approx. just over 5v to power up the usb. That I'm uncertain of. Any advice?

Yes, you can use 4004 or 4007.
The PIV voltage for a 1N4007 is 1000V, and 50V for a 1N4001.

Whoops, was going to re-type this one along along with the other message above as one comment, but you replied to it pretty quick :P

That should be OK.
Looking forward to see the result on instructables.

Had just a couple questions about this. I'm trying to build up a DS charger (I, in a sense, inherited my late fiance's when we were young minus a charger), and it said I needed a 5v voltage regulator. Yours looks super easy and fun to build, so my questions are thus:
Is the switch just for turning the power on/off, or does it have some less obvious purpose?
Could the 9v battery be replaced with something like an old phone charge to step (I belive they are around 12v) down?

1 reply

Hi maxxion,

>>Is the switch just for turning the power on/off, or does it have some less obvious purpose?
Yes, it's On/Off switch.

On the second question.
>> Could the 9v battery be replaced with something like an old phone charge to step (I belive they are around 12v) down?

Frankly, I never use this Regulator connects to the Power more that 9V battery.
Since it was designed specifically for 9V battery.

Anyhow here is a data sheet for the regulator IC (LM780L5)
It said the max. voltage input is up to 30V. With the current output of 100mA.
You can try it (AT YOUR OWN RISK!)

If I were you I would look into something like this
5V 1A (1000mA) USB port power supply. (http://www.adafruit.com/products/501)
It has USB port with it. And find USB to DS (power port) converter cable.
Or if you could modify the USB cable to suit the DS power port yourself too.

Hope this help!

Thanks to all the voters!
I do really appreaciated!!

Pretty drawings of the schematics! Nice and very useful project, thanks!

1 reply

On the label of my charger it says its maximum output is 700mA. But this regulator's max output is only 100mA. Is this going to be a problem? What could I do to increase the max output?