0
\$\begingroup\$

I was searching the web to get full knowledge of IR remote controls. My satellite receiver (Humax)'s remote control got ruined. So, I unscrewed the remote control took a look inside it. I know IR operates on 36KHz but what modulation techniques is being used. I just need to know the circuitry of the transmitter.

\$\endgroup\$
  • 1
    \$\begingroup\$ Not all remote controls use 36kHz. \$\endgroup\$ – stevenvh May 13 '12 at 13:26
  • 1
    \$\begingroup\$ What is it that you are wanting to do? With how your question is now you could either be wanting to make your own remote or you could be wanting to know how it works to try to fix the current remote. The answers will be different between the two questions. \$\endgroup\$ – Kellenjb May 13 '12 at 14:11
  • \$\begingroup\$ The circuitry won't help you at all. Typically it is a microcontroller, a transistor to drive the IR LED, the IR LED itself, and maybe (!) a series resistor. And a bunch of switches that are just PCB traces that can be sort-of shorted by the carbon/rubber of the buttons. All the magic is in the firmware in the microcontroller. \$\endgroup\$ – Wouter van Ooijen May 13 '12 at 16:33
3
\$\begingroup\$

You don't mention the word "protocol" in your question, but you must know that there's a number of protocols around, not everybody uses the same coding. That makes "full knowledge" a tall order. RC-5 Telaclavo refers to (as one of the most used) is totally different from the Sony SIRC protocol, for instance.

This page suggests Humax uses the NEC protocol:

"The Hex Code Generator for Yamaha is for NEC IR Protocol which is the same for Onkyo and many other manufacturers e.g. Toshiba,Humax etc."

Modulation is at 38kHz, not 36.

Details about the NEC protocol can be found here and here. The latter link also lists a few commands.

Building a replacement remote controller would be a silly idea; for a few dollar you can buy a universal, programmable RC.
If you really want to you'll need little more than a microcontroller. In the old days there were specific ICs for remote controls, the SAA3010 was the standard for RC-5, and was used in 100s of millions of remote controls. But today a microcontroller is as cheap. The program is easy: when you wake up on interrupt scan the keypad, and if a key is detected, send a serial datastream of the modulated code to the output. Repeat until the button is released and go to sleep.
There will be a transistor which drives the IR LED(s), and that's it. Most of the time a series resistor for the LEDs isn't even used.

further reading
Using the Philips 87LPC76x microcontroller as a remote control transmitter, NXP application note for an RC-5 remote controller.

\$\endgroup\$
1
\$\begingroup\$

Regarding modulation, and protocol, read Consumer IR and RC-5, both in Wikipedia. Copying them here would make little sense.

As far as the circuitry of the transmitter is concerned, an MCU that reads the keyboard (of the remote control) and drives an infrared LED is all is needed.

\$\endgroup\$
  • \$\begingroup\$ It's no use directing OP to a specific protocol like RC-5 as long as you don't know what protocol is actually used. The information about RC-5 is useless to other protocols. \$\endgroup\$ – stevenvh May 13 '12 at 13:45
  • \$\begingroup\$ The Wikipedia timing diagram shows a negative pulse between a "1" and a "0" bit. That pulse shouldn't be there! \$\endgroup\$ – stevenvh May 13 '12 at 13:51
  • \$\begingroup\$ @stevenvh The OP wrote "to get full knowledge of IR remote controls" and "Can any one provide me with an IR tutorial!!", so I understood the question as about IR protocols in general, not a specific one. The RC-5 is one of the most common protocols, so I think it is of use. \$\endgroup\$ – Telaclavo May 13 '12 at 13:54
  • \$\begingroup\$ Yes, but OP seems to have a pretty naive idea about remote control. He doesn't even mention the word protocol, probably thinks there's only one. I don't think the plural "S" refers to protocol"S". \$\endgroup\$ – stevenvh May 13 '12 at 13:57
  • 1
    \$\begingroup\$ @downvoter - please tell what you think is wrong here, so that Telaclavo gets a chance to improve his answer. \$\endgroup\$ – stevenvh May 13 '12 at 14:53

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.