Which Remote Control Extender Do I Build?
Circuit :  Andy Collinson
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If you are thinking of building a remote control extender circuit then you may be unsure of which circuit to use. This article describes circuit differences to help you make the right choice.

Mark 1:
The Mark 1 version will work with any Infra Red (IR) remote control equipment. Will also work with faster modulated (115KHz) satellite decoders but subject to the limitations below.
There is no filtering between the received signal and the photo-diode, which makes the circuit susceptible to noise and interference from fluorescent lighting and other noise sources. Due to a compromise between noise pickup and gain, the sensitivity from remote control to the photo-diode is less than 1 metre. Careful must be taken to position the photocell away from all light sources, including strong sunlight.

Mark 1a:
Will work with most equipement as in the Mark1 circuit. Now has immunity to daylight and flourescent lights.
The range from the handset to the circuit is less than 1 metre.

Mark 2:
The photo diode has been replaced by an IR module.High immunity from fluorescent lighting and increased range from remote control to the circuit in excess of 5 metres.
Relies on the small residual carrier present from the IR decoder to re-transmit the pulse. This circuit works best with older equipment (pre 1995) as no modulated carrier is added to the decoded signal. May not work on modern apparatus.

Mark 3:
All the advantages of the Mark 2 including generating a modulated 38KHz carrier. Uses the same components as the Mark 2 circuit plus a few additional parts.
The final pulse is inverted and some equipment may require "fine tuning" to work. Will not work with faster modulated appliances.

Mark 4:
As with Mark 3 but also has an adjustment to fine tune the modulated output. No inversion of the final pulse.
Will not work with faster modulated appliances.

Mark 5:
Should work with almost all handsets including the modulation range 30-120kHz. Has high immunity to daylight and flourescent light sources.
The range from handset to circuit may not be as great as the Mark 4 version.

What is my remotes modulation frequency?
The vast majority of IR remote controlled appliances use 36-38KHz. If you have access to either a digital counter or an oscilloscope then use this circuit to measure the modulation frequency.

Final Words:
If you only have one piece of equipment that uses a common 38kHz then any of the extender circuits will work. If you have multiple equipment that uses different modulation frequencies then the Mark 5 version should provide the best capability.

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