DIY Infrared Remote Extender Unit

Here`s a few details on the Infrared Remote Control Extender unit I designed and built to control my NAD T752 A/V receiver. The NAD T752 has an IR input socket on the back of it for system installs where the unit has to be inside a cabinet or at least out of normal Infrared control range. Many newer A/V receivers have this feature, and so it came
DIY Infrared Remote Extender Unit - schematic

as quite a surprise when I tried to find information about how to best take advantage of this feature and found that very little was available. I emailed NAD, and they suggested I obtain a Xantech Hidden Link receiver or similar. This retails at around US$80, and is certainly not readily available in New Zealand. I thus emailed them a few more times hoping to obtain info on the signal that the T752 was expecting on this port. Luckily they were happy to oblige with the information I needed, and armed with this and a perusal of the documentation on both Remote Central and the Xantech homepage I put together what I needed to create. The NAD T752 is expecting the raw IR information (An active high 3kHz signal with the NEC protocol) to be modulated with a 40kHz carrier, and to be active high logic with a signal level of around 5V (TTL levels). Thus I could quite easily modify the Mark IV remote control extender circuit found here to achieve my goal. The above circuit is layed out so as implementation on prototype board is nice and easy. The black traces are underside traces made with the component leads etc. whereas the red colours represent the components and any wire links (2 total) needed. The circuit is viewed from the component side of the PCB. It`s quite a simple circuit. The IR receiver module and other parts were purchased from Jaycar Electronics here in New Zealand - it is a 38kHz unit which handles the receiving of...

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