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.
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.
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.
breadboard pcb (cut in half)
0.1uF ceramic cap
1.0uF elec cap
330ohm resistor (for led)
5k potentiometer & knob
3mm led green (or red, or amber,etc)
2.1mm barrel jack adapter
2 x posts for output power
wires of various lengths 22 - 24AWG
heat shrink tubing (for exposed connections)
Altoids or similar sized tin
wall wart 9 volts dc with 2.1mm barrel jack
hot glue gun
brad point drill bits
files or sandpaper
dremel with sanding drum to enlarge/shift holes
I found brad point drill bits, although for wood, do an excellent job cutting through the soft tin of the Altoids container. Becauase of the side cutters on the bitface the hole made comes out perfect without a lot of fuss & bother using just a hand held drill. see hole in side of tin in drillbit image.
When drilling holes in top of tin I find it best to use a block of wood to support the tin while applying pressure so the metal doesn't warp. The two larger holes were drilled with a normal drillbit, hence the flat-sided circles. Washers when fastening components to the lid will hide these irregularities. The smaller holes were drilled with a bradpoint and thus are clean & round.
The 2 caps, 2 resistors and any wires needed on the board can be soldered in place now. I used solid core here & stranded wire for all the wires that need to flex when the tin is opened & closed.
I believe in repurposing electronics so you might have noticed almost all parts used here have come from other electronics, or in the case of the container, from numnums! I do test all parts with a digital multimeter before soldering in place. As far as cost for this project I'm sure a lot, if not all, these parts can be found in your parts bins. Personally, I bought the Altoids - 2.20, circuit board - 1.50, toggle - 0.50, green led - .20, & the green solid core wire - maybe a few cents. Under 5 bucks - not bad!
I find a clean, well-lit workspace to be ideal. Wish it would just stay that way!
Hope you enjoyed & it will be a pleasure to hear your comments! Be safe & re use, re purpose when possible.