I've got a 4 year old LG TV remote control, which I recently took apart.

I've also got a Popcorn Hour A-100, without the original remote.

So my question is - given that I don't care about the plastic packaging - is basically how to transform the old TV remote into the NMT (Networked Media Tank) remote which I require.

I'll divy it up into 3 seperate questions:

  1. Is there a way of finding out which IR signals are required to operate a specific device, namely my NMT?
  2. Is there a way of finding out which IR signals a remote puts out, with the push of every different button (or am I approaching this all wrong, and the push of a specific button does not trigger a different IR signal,but merely sends the information to the micro-processor which in it's turn tells the IR signaler what to do) ?
  3. Lastly, is there a way to re-calibrate a remote so it puts out the IR signals I require?
  • \$\begingroup\$ Under low lighting conditions, view your remote IR diode with a cell phone or web cam. If your eye is fast, you may be able to see the blink pattern. Without the original that you want to duplicate, it's not likely that you would guess the required Start/Stop pattern. \$\endgroup\$ Jan 4, 2014 at 21:07
  • \$\begingroup\$ @Optionparty - There is no way that a camera system or human eye can see an IR remote control transaction fast enough to discern the modulation pattern. IR controls typically send a transmission, which can consist of quite a few pulses, in less than 100 msec. The typical key code repeat rate, when a button is held down, is 10 times per second so the total transmission time for one sequence has to be less than the 100msec for the repeats to work correctly. The web cam / digital cam idea is only a good technique for checking if an IR remote is alive or dead. \$\endgroup\$ Jan 5, 2014 at 0:54

1 Answer 1


IR Remote controls are generally designed to be tight to their functional requirement in order to keep their manufacturing cost extremely low. This generally means that the chip in the remote is a dedicated chip designed to produce a certain IR protocol that is specific to the manufacturer's device family.

Each key on the remote will cause a different IR modulated sequence to be sent to the target device. All of the key codes for that target device will be within the same IR protocol family. A protocol family will support a certain number of key codes within the protocol whether that be 32, 64 or 128 codes (or some other number). I mention this because some remotes can support multiple target devices for example TV, DVD etc. Each target device may be a different protocol family. There are handful of different protocol families in use and are generally lined up with major equipment manufacturers such as Sony, NEC, Philips and others.

It is highly unlikely that the remote that you have in hand will be easily convertible for use with your alternate target device. You would have to first know what IR protocol family was required for your target device and what the required individual key codes are. Unless you have the actual remote in hand this information is almost impossible to reverse engineer. The best you could hope for is that the family protocol and key codes may be documented off on some web site.

If you did manage to find the target device family protocol and key codes then the process of converting the existing device would only be successful if it natively supported the same IR family protocol. It is usually possible to reverse engineer the IR protocol and key codes for an in-hand IR remote control. Two general methods are used for this, both of which require the use of an oscilloscope. With one scheme you probe the signal in the remote itself that drives the transmit IR emitter LED. In the second scheme an IR receiver component can be rigged up on a proto-board and then used to receive the signal from the remote control which is then probed with the oscilloscope. The latter scheme is somewhat easier to see the IR signalling envelope because the IR receiver removes the carrier frequency from the detected IR stream. At the transmit side you would see this carrier as part of the waveform and is typically 36KHz, 38KHz or 40KHz although other carrier frequencies may be used by some IR protocol families.

In the long run you would probably be best off to look into finding a replacement remote control for your target device or look at universal replacement type controls that can be programmed to emulate the IR family protocols and key code sets for several thousand different target devices. Even if the universal remote does not directly support your target device it is possible to sometimes experiment with selecting alternate similar type device selections and find one that will allow partial control of your device.


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