The 78XX family of linear voltage regulators can be very handy to have about when bashing together experimental circuits. Cheap, proven, easy to fabricate and using a minimum number of external parts, they are near indestructible but can still suffer physical injury when flopping around the benchtop or tossed in a drawer for some future calling. This Instructable simply offers an inexpensive way to safeguard this important resource using scrap and salvaged parts.
Step 1: The Easy to Do Build...
The image is rather self explanatory but here’s what you do:
- Use an awl or sharp tool to punch a hole through the screw cap. Fish a short length of 5 mm corded plug through and knot the end to provide a strain relief function.
- Drill or ream a hole with a file tang into the vial's bottom to mount the female 5 mm receptacle type you have on hand. The one I used had a threaded nose— most common ones have a threaded back barrel and will require lead wires soldered to it before mounting so as to facilitate soldering to the circuit board after tightening the nut.
- Construct the regulator circuit on perfboard using any of the vast number of data sheet examples found online, and make the interconnects to the plug and cord. Obviously you can choose the voltage most suitable for your needs but be advised external heat-sinking is impractical for this housing so try and keep your source voltage near to but slightly higher than the desired output voltage (typically 2.5 volts).
Some nice things about this approach are that excess cord can be stuffed back into the bottle cavity, and operational data can be written on the body with a Sharpie pen, such as output voltage, maximum input voltage, maximum suggested current draw, etc.