Switching between DVB-C and DVB-T signals

Nowadays, newer TVs has one common antenna input for DVB-C and DVB-T signals, which is the case for our Panasonic TX-55AS750 TV as well.
The TV is able to scan all channels into separate channel lists for the DVB-C and DVB-T signals.
Combining the signals with a simple T-connector wont work, as many of the TV channels overlap.

One option is to buy an extra DVB-tuner and connect it to the HDMI input!.. and an extra remote for the DVB-T channelselection. BUT on the Panasonic TV remotes, I have used for testing, you will find a “TV” button to toggle between the DVB-C and DVB-T channel lists.

The challenge is to make a piece of electronics that can grap and detect the infrared signal of the “TV” button in order to control an antenna switch connected to the common antenna input of the TV. The installation set-up came up to look like this:

I ended up using 4 remote control buttons for the infrared receiver:
1. “TV” button to toggle an antenna relay with signal inputs for DVB-C and DVB-T.
2.When the “Exit” button follows the “TV” button the antenna relay is toggled, just in case the TV and the relay are out of sync.
3.When the “eHelp” button is followed by the “Exit” button, the output for the antenna LED light is toggled.
4.When the “lastView” follows the “TV” button the antenna relay output is toggled. Successive “lastView” will toggle the antenna relay output as well.
The antenna relay I use is the Spaun SAR 12F, requiring a voltage supply of 10..20 V DC @ max. 35 mA provided by an external power inserter, and a 5..18 V DC @ max. 1.5 mA for the relay control signal. The relay datasheet is here: SAR12F

The electronics I made for the IR receiver and antenna relay controller :

A Sharp GP1UX511QS 38 KHz infrared receiver is used for receiving the signals from the Panasonic remote, but any 38 KHz infrared receiver should do the job. At the LED connector, 2 high brights LEDs can be added to indicate the DVB-T signal is switched to the TV and to indicate the antenna LED is turned on.

On request, I can provide a zipped version of the Eagle design files.

The 12 V power inserter is a stripped down and modified version of the Triax FP501 power inserter.. The 230 V AC supply and the internal 78L05 voltage regulator are removed. A 12 V DC connector provides power to the inserter via the black plug shown in the picture above.


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