Customer Service And Infra-Red (IR) Remote Controller
This story started with an unpleasant – but unfortunately too frequent – customer service experience. Remember the quote: “Satisfied customers tell three friends, angry customers tell 3,000”… As electronic repairers you know this and will do your best to satisfy your customers. It is a matter of business survival and self-satisfaction.
Unfortunately this doesn’t seem to apply anymore to large companies as we have seen a degradation of service quality over the time, to the point that it became disastrous in some cases. A few days ago my TV remote controller stopped working. Changing the batteries did not solve the problem and I could not see any flashing IR light – looking through a camera – when pressing the buttons. As it was still under warranty and didn’t look easy to open without leaving traces, I decided to go to the shop where I bought the TV. It’s a big store and it was not busy. Half a dozen sales people were hanging around paying no attention to customers entering the premises, even turning their head into another direction if they would see one; I had to call one of them for service. As soon as I removed the remote controller from it’s envelop the man immediately said: “No, this not, this one cannot” and walked away before I had the opportunity to say a word! I ran behind him and explained that I bought the TV from them a year ago and it was still under warranty. “You must go to the service center” the man said and, again, walked away. I had to run after him, again, and ask if he would, at least, give me the address of the service center. Reluctantly he went to a computer, brought the address on the screen, and told me to use my mobile phone camera to capture the address. Wow, what a service, I felt so unwelcomed and that guy was just eager to get rid of me. Thank you very much salesman, sorry to have disturbed your snooze… I learned my lesson, next time I go straight to Google and try to find the information myself.
I remember the time when large radio-TV and electrical appliances stores hired technicians to help customers with their technical queries. A few of my friends took this kind of job after their apprenticeship. Gradually this service disappeared, cost cutting of course, and the technicians were replaced with cheaper salespersons, most of them having no idea about technical matters. This was a different time, when customer service was considered as an important part of the sales, boosting the sales, instead of an annoying cost center…
The following day I went to the service center and learned that I had to buy a new remote controller because it was not included in the warranty. What do you expect, warranty/extended warranty never covers the parts that are more likely to fail! Anyway the service was OK and I got a new remote controller in less than two days. And the good news is that now I was allowed to break open the old one!
This is the type of device where we need a blade or a mini-crowbar to take it apart! There are many videos on YouTube showing how to do it and they are very useful, if only to tell you if there are hidden screws, which was not the case for this model.
As expected, there is not much inside, an electrolytic capacitor, a smaller SMD capacitor, the IR LED transmitter and an IC. And the keypad of course! The capacitors and the IR LED tested OK. There were no damage, corrosion etc… on the keypad so the only possibility remained the IC. The IC is labeled ADAM27P16G and is a 4-bit single chip microcontroller. With software inside obviously, so nothing can be done to salvage the poor remote controller except recuperating the caps and the IR LED.
Nevertheless this minor incident gave me the idea of finding a bit more about those IR remote controllers. One might think that all it takes is to send a digital word made of ones and zeroes to a transmitting IR LED then collect the signal at the other end using a IR phototransistor and pronto. Well, not any more, this might have been the way in earlier remote controllers but not anymore!
On the receiving side, TV, DVD etc… the designers usually specified an Infrared Receiver similar to the 1838T, which I will use for a couple of experiments: If you power the 1838T as shown below and connect its output to a LED through a 1k resistor you just built a simple remote controller tester… The LED will be flashing when you beam a remote controller at the device and press a key. And this works from far away, from the other end of the room for example. What a nice and easy remote tester, using only 3 components…
On another end, if you beam a constant source of IR or white light (that contains IR in it) the circuit doesn’t seem to react. You might see a glitch when you turn on or off the light. The device is expecting a particular type of pulses, not any kind of pulse.
A glance at the datasheet shows that the IR receiver is a more complex circuit, designed to decode pulses made of bursts of a 38 kHz carrier frequency, as shown below:
The following figure shows the bloc diagram of the device. We can see that there is much more than a simple phototransistor…
What a clever idea. It makes the remote control totally oblivious to any type of optical interference such as ambient light or other kinds of light, but reacting only to its own specified pulses.
To measure this I added another detector to my test rig, a simple phototransistor, without any additional circuitry, which should show us the real signal while the output of the 1838T will show the signal after decoding:
And here is what we can see on the oscilloscope:
Channel 1 (Yellow) shows the signal as it is received and Channel 2 (Blue) shows the signal after decoding. Let’s have a closer look:
How to interpret the digital output is another question. To avoid interferences between different devices, for example TV, DVD, sound system etc… manufacturers use different codes. There are also different protocols used by different brands. This normally works fine. However I remember a friend who was getting crazy as her ceiling fan was turning itself OFF randomly. She had it replaced, had the remote replaced, had the electrical installation checked, not to avail. It was during a gathering in her house to watch the football world cup that one of us noticed that the ceiling fan would stop when we changed the TV channel…
Some codes can be found at the following link:
Besides my whines about customer service (I had to get it out!), this short article demonstrated what happens behind the flashing IR LED that we can observe with our mobile phone camera. If you like to play with microcontrollers like Arduino or others, there are applications that allow you to read the codes of your remote controllers and even make your own remote. Have fun and be kind and patient with your customers.
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