Picture of LM317 portable voltage regulator
 First Instructable for me. I've been wanting to build an adjustable voltage regulator in an Altoids tin for quite some time. A variable voltage of between 1.2 & 6volts for testing small dc motors and LEDs retrieved from old electronics would satisfy my needs.Googling the net for project designs surprisingly didn't produce any results. I thought "See a need, Fill a need!" & thus began this project. I've been tinkering in electronics for only a few years now. I don't pretend to know much & appreciate any & all mistakes being brought to light so they can hopefully be corrected. 

With a DMM attached to the output posts to accurately set the voltage one could also power an Arduino or other small project. Using a 9 volt dc battery connected to a 2.1mm barrel jack it's small enough to fit in yer pocket & so totally portable.

 I consider this a fairly simple & fun project leading to a totally useful & versatile tool when complete. Soldering on the breadboard pcb is a bit challenging but a decent iron with small tip makes short work of it. 
Remove these adsRemove these ads by Signing Up

Step 1:

Picture of
  Project Description:
 With 9 volts dc provided by wallwart or battery a project can be supplied with between 1.25 - 8 volts dc by connecting to 2 posts with alligator clips or bare wire. A toggle is included for on/off with an led to show when powered up and a knurled knob for voltage adjustment. All electrical wiring & components safely contained within an Altoids tin.

 After making who knows how many drawings attempting to fit this circuit into the tin I found putting it down on graph paper allowed me to see where everything goes quite readily. I've just drawn enuf to get the gist of it. It is a regular breadboard after all with double power rails top & bottom (tho I have only used the negative rail) & 2 solid rows of 5 holes high each.

 Figure 30
 Is Texas Instruments datasheet. You'll find an almost identical schematic when googling Nat Semiconductor, Fairchild, et al. This is the basis of my design. Please note the R1 resistor here is 240 ohm, I've replaced it with a 470 ohm for a reason I've now forgotten but I do remember reading somewhere this value should be 100 - 500 ohm.

 The 3rd image is a page of my design notes showing the late stages of how I arrived at this particular configuration. I've actually been working on this for over a year, off & on, with the project only coming together during this past month.

How has this lasted you over the years? I found that altoids tins need a bit of insulation to keep the parts from sliding around and eventually breaking. Also, moisture can be a problem, rust can accumulate have you found that this has happened to you?

What utility does this serve? Just curious, I am not extremely well versed in the function of voltage regulators. Nice work! One thing that I would love to see is a digital version of the blueprint plans. It is kinda hard to make out with a picture of a drawing.

Hello envirolutionary, Thank you for your comments.

In answer, as a small power supply it has held up quite well with no sign of rust (yet). I would suggest applying some light machine oil on a cloth & giving the whole can a wipe. Should prevent any rust as long as the air where you are isn't tropically humid. lol. The stiff solid core wire I used keeps everything inside the tin rigidly in place.

I built this voltage regulator to supply power to small projects. At the time I was disassembling various electronics & felt this a worthwhile endeavour. Since building this I now have a 30V 5A adjustable power supply with digital readout that better suits my needs. I must admit my drawings worked well for me but might not be the best for others. I need to investigate Fritzing I suppose. If I can I'll see about getting some better schematics up.

Thanks for your interest!

terrible tinkerer (author) 2 years ago
Thanks for the input pfred2, I did find some very useful nuggets of wisdom, man you are leagues beyond where I'm at & I appreciate your views. Yer method of determining the value of current limiting resistors by jumpering a pot, ingenious! I've been struggling to understand the "equation" method, which really takes the fun out of things, whereas yer "hands on" approach is right up my alley! Very Cool!
pfred22 years ago
I've built a number of regulators based on LM317 ICs. You may be interested in looking at one I've posted here for some circuit layout ideas.