Adjustable Power Supply
A general purpose dc power supply
When testing electronic projects a good adjustable power supply is indispensable. The LM317 provides the basis for a quality regulated dc power supply.
This kit combines an LM317 with a thumbwheel potentiometer to allow you to easily set the output voltage from 1.5V up to 2V less than the input. Three preset voltages (5, 9, 12V) can also be selected. Input power comes from an external source such as the power adapter available below.
The kit includes a circuit board, parts, and a printed manual. Kit assembly requires soldering and some of the parts are surface mount. If you've never soldered surface mount parts before, you may be surprised to discover how easy it is. See the manual for more details.
How to make an enclosure using an iPod box!
Download Manual (PDF 300KB)
APS Adjustable Power Supply Kit: $15.95
12VDC, 500mA power adapter (2.1mm plug): $5.95
An enclosure using an iPod shuffle box!
The Adjustable Power Supply fits nicely inside the clear plastic box that the iPod shuffle comes in. There is room for a potentiometer and output terminals as well. The picture below shows the iPod box after drilling a number of holes.
You will need to determine the hole diameters based on the type of terminal posts and potentiometer you use. The hole on the back panel provides access to the dc input jack. A few extra holes on the right side and the cover are needed to provide ventilation for the LM317 on the APS board which can get hot.
Assemble the APS board. Shown below is how it looks when assembled as described in the manual. If an external potentiometer will be used, as in this case, the following components are optional: R2, R3, R4, R5, JP1, JP3.
Next, solder #22 AWG or similar wire to the terminals on the APS board at VOUT+ and VOUT- and at both terminals at JP2 (these will be used later to connect to the terminal posts and potentiometer). After assembling and testing the APS attach 4 standoffs to the board and then use glue or epoxy to attach the standoffs to the enclosure.
Then solder the wires coming from the board: connect VOUT- to the black terminal post, VOUT+ to the red terminal post, ground terminal of JP2 to the potentiometer CCW terminal and the other terminal of JP2 to the potentiometer CW and wiper terminals. Clear tape can be used to secure the plastic cover to the base.
The finished power supply is shown below. The potentiometer is a precision 10-turn unit that provides good voltage adjustability. A standard single turn potentiometer could also be used.
To build one you will need the following:
APS adjustable power supply kit
clear plastic box from an iPod shuffle (3 3/8 x 2 5/8 x 1 1/2 in, WDH)
5k potentiometer
knob for potentiometer
red terminal post
black terminal post
(4) threaded stand-offs
(4) machine screws to fit stand-offs
#22 AWG wire to connect potentiometer and dc output terminals
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