iPhone as a frequency generator
To show that iPhone is not just a fashion accessory, as many like to say, read below how to make it a useful device. It is a frequency generator with solid characteristics. Quality will satisfy the needs of amateur electronics and it will be sufficient for the basic measurements and adjustments in audio technology.
Only two components are required, assuming that you have the iPhone:
- Application "Freqgen" which is free and available in the AppStore.
- Adapter that you have to make. Construction is very simple, and the whole process is shown below.
Is a frequency or test tone generator application over the range of 20Hz - 20 kHz, and it is possible to choose between waveform: sine, square, triangle and saw. Thanks to quality of audio output for headphones, which is built into iPhone, frequency accuracy is very high. The output is near CD quality (44,100 samples per second, 16 bits/sample)
Frequency is selected by typing the numeric value in the box with the keypad, rotary selector, using a small keyboard at the bottom of the screen, or by shifting octaves with octave up/down buttons.
The first thing you need to get is a 3.5mm plug, the iPhone uses version with 4 pins, but also receives regular with 3 pins that you can find on regular stereo headphones. My adapter is made from old stereo headphones. We need only one cable, so the other can be removed like shown on picture below. Plug is factory connected with shielded cable so no soldering is needed on plug, unless you use new 3.5mm plug. In this case, solder shielded cable to selected pins.
A short video of everything in use: