Raspberry Pi Zero is an amazing product, and some people are asking if it is possible to transmit magnetic stripe information using the Zero with AudioSpoof.
The main problem with this Raspberry is the absence of a sound output(jack). So it is the first & main limitation. Initially, I thought about the Adafruit device: Stereo Speaker Bonnet. It is a 3W amplifier, but without the possibility to control the volume on the board made it not feasible. Are you asking why the volume control is that kind of important? It is necessity to adjust in real-time the volume depending of the size of the coil and the amplifier’s power.
One of the main problems with the amplifiers on the gpio is how much voltage consumption the amplifier will drain. That is a priority.
Thanks to Lady Ada(I love you!) and her amazing support to the community, we can add basic audio output to the Raspberry Pi Zero version using a simple circuit:
This output by itself is not enough powerful to generate strong magnetic waves to be detected by the card reader; so we have to add a simple amplifier. To do this, I will use the LM386.
It is a simple pinout, the pins: 2 and 3 are the sound inputs. 5 is the + output. By default the voltage gain is 20. If we add a 1oμF capacitor implementing pins 1 and 8, the gain will be 200. However, I will try to keep it simple just as reference.
That could be an easy way to have “volume” at least. More detail about LM386 please visit: http://www.techlib.com/electronics/audioamps.html
To save time and to make the proof of concept video, I decided to buy a small amplifier: DROK Super Small 3W+3W DC 5V
So now everything connected, we can test it; the white card is basically my coil:
Proof of concept:
AudioSpoof code: https://github.com/salmg/AudioSpoof