Manage any AV equipment from your phone. IR Transceiver for JACK 3.5

On September 26th, HackDay # 32 started in Penza . We decided to take part and implement an IR transceiver for JACK 3.5. The main requirement for our device was compactness and non-use of power sources.

We started our work by intercepting the signal from the control panel and examining its waveform. To receive the signal, we used the usual IR diode:


For the analysis of the signal, we used the Audacity program:


The received signal is extremely clean.

The diode acts as a demodulator and we do not know at what carrier frequency the signal is transmitted. To solve this problem, they downloaded an example of a signal from the resource that needs to be submitted for a Samsung TV, and using the same program they began to investigate.


The stereo signal is amplitude-modulated to a sawtooth signal with a frequency of 20 kHz, inverse for each channel. Presumably this is due to the fact that JACK can stably generate a signal with a frequency of not more than 20 kHz and a diode is connected to each channel. The signal is inverted so that the IR diodes are triggered on different fronts.

By changing the previously caught signal by this algorithm and making a transmitter specifically for this algorithm, we started testing.

Here the earth is not used, the diodes are connected opposite to the left and right channels.

The circuit worked, but we were not happy with the presence of 2 diodes. We decided to connect our receiver to this track, he also controlled the device. Therefore, their track is redundant and we left only one channel.

This solution only works on PCs and some smartphones from a distance of no more than a couple of meters. I really did not want to use an additional power source, but nowhere to go. To amplify the signal, we used a simple transistor switch.


The circuit has lost the ability to receive a signal. In the future, you can refine the circuit, we switched the receiver and transmitter.
For testing, we used a BBK DVD player and a Tricolor JS 7300 receiver. Our receiver is capable of controlling these devices from a distance of about 15 meters (how much was the corridor). At the demonstration of the projects, we wanted to control the ViewSonic PJD 5132 projector from a smartphone. It’s good that we decided to check the performance in advance - nothing really worked. The projector perceived our control signals only if the transmitter was brought close, which was problematic because it hung from the ceiling.

We decided to “play around” with carrier frequencies. When the frequency changed, our test devices began to work similarly to a projector, therefore, it is impossible to superimpose an information signal on the same carrier. In the course of long efforts, we selected the frequency and the demonstration did not break.

An application for a smartphone that automatically modulates the read signal was not made. We recorded ready-made audio tracks on the phone and styled the Activity similarly to the control panel.

In the near future we will complete it and post it on Google Play in the public domain. Its main features will be training in device commands and the ability to create a personal remote control.

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