Which Remote Control Extender Do I Build?
Circuit :  Andy Collinson
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Introduction
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:
For:
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.
Against:
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:
For:
Will work with most equipement as in the Mark1 circuit. Now has immunity to daylight and flourescent lights.
Against:
The range from the handset to the circuit is less than 1 metre.

Mark 2:
For:
The photo diode has been replaced by an IR module.High immunity from fluorescent lighting and increased range from remote control to the circuit in excess of 5 metres.
Against:
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:
For:
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.
Against:
The final pulse is inverted and some equipment may require "fine tuning" to work. Will not work with faster modulated appliances.

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

Mark 5:
For:
Should work with almost all handsets including the modulation range 30-120kHz. Has high immunity to daylight and flourescent light sources.
Against:
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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