field-guide-to-salvaging-sound/src/content/recipes/power-supply/index.md

title	BOMTable	order	shortDescription	BOM	Connections	pcb
Power Supply	true	0	Create a power supply for your future circuits	type count value Capacitor 2 10uF type count value Resistor 2 10Ω type label Misc 2x 9V battery clips type label Misc 3 conductive nails for the +V, -V & GND pins	-9v +9v GND	/recipes/power-supply/PaperCircuit.svg

This circuit provides -9V¹, 0V/Ground and +9V outputs, by combining two 9V batteries. If your project requires it, you can use any kind of battery instead of the 9V one, as long as they're two of the same ².

You could skip the capacitors and resistors and just connect the batteries together. However, they help filter electrical spikes, making the output smoother ³.

Testing

Before plugging in the battery's, check your connections⁴. When the batteries are plugged in, your pins should read -9V and +9V⁵.

Upgrade

An upgrade that could be useful is adding a power switch and/or LED to show if the power supply is active.

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1. Some chips, mostly op-amps, require a negative voltage, which does not come out of a battery by default. ↩︎

2. You can also get 18V: treat the -9V pin as 0V, making the 9V pin 18V ↩︎

3. { height=30px } ↩︎

4. You can test this using the continuity mode on your multi meter, which beeps if electricity can pass trough. ↩︎

5. Test this by using the volt meter on the multimeter. One probe touches your ground pin, the other the pin you'd like to test. ↩︎