How to efficiently control my dumb TV via Alexa?

Question

I have a more or less dumb TV (Toshiba 42SL863G) and home cinema system (LG HX806SG) which I want to control via Alexa voice command. At least switch them on and change into either TV or home cinema configuration. Unfortunately that seems to mean that I have to send some infrared commands.

The best solution I could find so far would entail a Raspberry Pi and enhance it with a custom build infrared transceiver like the one detailed here. Thus, I'd have a Raspberry Pi which I could then use with the LIRC library to control my dumb devices. Of course, I'd need to find out all the IR codes and then write a few scripts to trigger them in a sequence to set a mode like TV mode or home cinema mode.

The next step would then be to either outfit my future Pi with a ZigBee module or Z-Wave module and try to fake being a generic smart home device for Alexa or write a custom Alexa skill to trigger the Raspberry Pi scripts somehow.

That does not seem very direct. However, I seemingly can't find a more direct way to control these dumb devices. On the plus side that Pi would be a universal infrared command center.

Is there a better way to reach my goal?

Answer 1

Your approach seems to be the best you can do, since the models you've listed don't support any sort of integration with Alexa (and I think it would be infeasible to modify the TV/cinema system directly to connect it to your network).

The Logitech Harmony Hub seems to take a very similar approach of simply sending infrared signals to control 'dumb' devices (just like a traditional universal remote would), so it seems likely that your approach of using an infrared transmitter is correct (otherwise Logitech would have likely gone with a different solution to the problem!).

From the Logitech website, here's a description of how the Harmony Hub operates:

CLOSED CABINET CONTROL

Control your devices behind closed cabinets and doors with IR, Wi-Fi and Bluetooth® wireless.

For your specific use case, infrared (IR) is the only transmission type you need, since your TV and home cinema don't support the other methods.

However, on this note, it may be worth considering whether it's actually worth building it yourself as opposed to just buying the pre-built solution from Logitech for this purpose. I've checked compatibility for you using the compatibility checker and both your devices are listed as supported, and your method of using the Pi may be similarly expensive (but will also require the trouble of designing the software and finding the IR codes):

• Raspberry Pi 3 Model B - £32.99

From the guide you linked, here are the other parts required:

• Adafruit Protoboard - £10.13
• Two IR LEDs - £0.334 each
• Two LED holders - £0.097 each
• Transistor - £0.083
• 10 kOhm resistor - £0.167
• IR receiver - £0.471
• Hook-up Wire Spool Set - $15.95 ≈ £13 as of December 2016

(full model names omitted, and prices quoted as cheapest when this post was written for 1 unit)

When you total these, the price comes to approximately £57.70, which saves £41.30 compared to the Logitech Harmony Hub, but you will have to spend time designing the software to control the IR transmitter/receiver and the Alexa skill. Alternatively, if you decide to integrate it with SmartThings with the ZigBee/Z-Wave components you listed, the totals will be approximately £84 and £114 for the whole device (the latter is more than the £99 Logitech Hub!).

You may be able to reduce the price significantly, though, by using a more simple microcontroller, since I doubt it will be so complex that a Raspberry Pi 3 would be required.

In summary, if you're in for a challenge and don't mind getting your hands dirty, you could save quite a lot of money by designing it yourself (as long as you avoid the really expensive components). If you want convenience, Logitech's solution seems ideal since the integration with Alexa is already there and you also get control via your smartphone for free!

Answer 2

I had the same problem. Building infrared transceiver is a quite difficult task ( at least for me) I tried soldering all the components together and it did not work.

So, I looked for a board which does this and i found this irdevkit.com 26$ and ordered 1. I just tested it and it works! You can hook TX, TR to your development board to commuincate with the IR controller. To record an IR signal send E0 to the controller and it will start the learnning mode. To transmit IR code send E3 followed by the ircode.

Then I used a library to emulate my dev board as a wemos switch and Alexa started responding to my dev board as if it is a WeMos switch. Now I can turn on/off my tv using Alexa.

Hope this will helpful for someone else.

Answer 3

You can use HDMI CEC. The Raspberry Pi hardware supports HDMI CEC and so are your devices, you can then use the libCEC library to send commands over HDMI