Instructables

Make A Breadboard Power Supply

Picture of Make A Breadboard Power Supply
This was a weekend project that I did so I can use a breadboard and get power to it. Some of my projects involve using 5V for a logic supply, while for others I may need a higher voltage. In this instructable I'll show how you can use a fixed voltage regulator as a adjustable one. The advantage of this is method is that your minimum output voltage isnt 2V, such as in the LM317T, but your minimum is what ever voltage regulator you used. For example, in this project I use a LM7805 as a adjustable Regulator, It gave an adjustable Voltage from (Vin-2) to 5V. I say Vin-2, since there is about a 2V drop across the regulator.

The Main reason for making this is because I wanted to make a portable breadboard with a Power supply in case I was bored at someones house, had a circuit with me, and wanted to play with stuff. This orignally stemmed from me salvaging a BUNCH of Mosfets/Transistors and not being able to test them when I was away for a weekend. Thus, this thing is powered from a wallwart or anything that has a 2.5 mm Plug
 
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Step 1: The Design

Picture of The Design
I needed a PSU that gave both 5V and was adjustable in case I needed 12V. Granted, I could have used a LM317 AND an LM7805, but because Of board space, I couldn't use both. I could have used Just a LM317 Adjustable Voltage regulator, But I didnt feel like breaking out my volt meter if I needed Just 5V.

Then I looked around the web and found that a Fixed voltage regulator can be used as an adjustable version. The reason why this works is that it makes ground "float". By adjusting the pot, your adjusting the ground point seen by the regulator.

The switch shown in the schematic is optional. I removed it from the final design (but its still on the PCB). I later figured I can just remove the power Plug and use that as my switch.
Olivierh1 month ago

if you don't want to build it yourself, there is cheap power supplies on the internet and I think that would be cheaper

http://voltatek.com/en/home/27-breadboard-power-su...

rwaqar2 years ago
how van i use it to give me -10v ??
could you use a perfboard
Jodex4 years ago
Resistors in my local electronics store are so freaking expensive; Almost two euros each! Witch is about 2.8$ !  Once I planned making a guitar distortion pedal and just to spend time I counted how much the resistors will cost on that one and I got about 37€!
knektek Jodex4 years ago
well what i do is get a schematic of what you are doing and show it to your IT teacher. just say that i need the parts but i dont have them. i got a load of battery holders, caps and pots!
oli1122 knektek4 years ago
 Lol iv done that to tis easy make friends with ur DT or IT teacher and say its a project and hes like here's the key to the parts room take what u like LOL XD
knektek oli11224 years ago
now im at a place where i can spend £50 on electronics! cool
i'm lucky, in the philippines, i know a supplier just 5 minute travel by jeepney and walking. Their resistor costs .25 pesos, about .005 dollars, and well, their breadboard is 120 pesos, or frickin 1 dollar 40 cents
online bullshit cant beat these prices...
BTW, if you do live in the philippines, name is wiltron general merchandise, tel # 8821886 AND i am not advertising them, just for FYI's sake...
cdousley4 years ago
 i got the same breadboard, "But the crumbs get stuck in the holes."
phillyj4 years ago
When I try to download the schematics, the .sch file is saved as F03P09IFN82TDBA.tmp I just wanted to see it so I'm using Eagle 5.6.0 Light freeware. First time using Eagle also. Any ideas?
Nerdz (author)  phillyj4 years ago
Instructables did something to the file (for whatever reason). Just rename it to what it shows (PSU.Sch and PSU.brd). It works for me using this method.
Nerdz (author) 5 years ago
Id like to add Ive been using this module for a couple months now, and Ive noticed there are some problems;
  • While plugging in and taking out the adapter, the PSU might come out of the board, so to prevent this, you have to hold it down
  • While doing so, you might accidentally increase the voltage. Not good for TTL/PICs/AVRs :(
  • The Regulator gets a bit warm, although this isnt a bad thing and is to be expected.
frollard5 years ago
Good job on hitting hackaday! Anyhoo, great project - looks like it could be easily laid out on veroboard as well! I need exactly one of these.
Nerdz (author)  frollard5 years ago
I Hit Hackaday? =D =D =D

I also in the process of designing A SMPS version of this board, but it will be fully adjustable, since I dont know if the same trick will work with SMPS. But this may not be built because of lack of funds. It will Be SMD and I'll try to get it to fit on the same board-which is a challenge.

I could have made it 3.3V, But I dont need myself ever needing that voltage-unless I start getting into dsPICs or SD card communication.
Nerdz (author)  Nerdz5 years ago
And heres the link for those who are curious:
http://hackaday.com/2008/11/08/adjustable-breadboard-power-supply/
nice project!
for people like me w/o mad pcb making skillz, sparkfun sells a kit like this
http://www.sparkfun.com/commerce/product_info.php?products_id=114

http://www.curiousinventor.com/kits/bread_power
gmoon5 years ago
Great! Simple, inexpensive and utilitarian (I'd be surprised if commercial versions don't turn up soon.)

BTW, the Instructables interface includes drawing "highlight" boxes overlaying your images. Each box has a mouse-over text box you can customize....
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