Trying to replace an IR remote for a mini-split (heating and air). Ardunio?

i've got wall mounted ac unit (kind of mini-split setup) uses ir remote control operations. here's don't it:

* there no real on/off "thermostat" function. can choose temperature, unit run forever (cycle between ac or heat , fan/vent) until turn off.
* remote crappy, , have aim precisely response.
* interesting modes dehumidify, different fan speeds, air flow direction, away/low power mode, etc (all things helpful), useless since have manually change them time remote effect, , nothing automatic.

my idea make kind of device can program accept input (initially via usb or ethernet, via small lcd buttons), read temperature , humidity in room, work sorts of software magic (i'm software developer trade; i'll bring magic) , send ir codes ac unit manage it. know i'll need following:

* sort of programmable logic board (thinking arduino right this)
* ir transmitter/blaster (preferably 1 cord can mount directly front of ac unit reciever is)
* ir receiver (temporarily only? need read in , make database of every possible code current ir remote can transmit)
* temperature sensor
* humidity sensor
* small lcd input buttons (eventually, not needed initial config)

challenges:

* 1 way data flow; there no way tell if device doing should be. there wires can potentially tap extremely basic info, unit under warranty , costs several thousand dollars.
* don't know type of ir signal remote uses (what frequency, string length, etc), don't know breed of receiver/transmitters need.
* have never tinkered arduino before; no experience on part (though coding skills strong)

i'd love feedback on plan, , maybe point in right direction on potential parts. i've been looking @ hardware options, , frankly i'm confused.

potential parts i've found far:

temprature , humidity sensors: dht11 or dht22 ($2.50 or $11; not sure if need upgraded one)

having done similar, can tell tough 1 reason: communication between remote , split unit 1 way. means unlike simple tv remote (which sends different ir code each button pressed), state info (fan speed, temp, etc) stored on remote itself. when press button on split unit's remote, send whole stream of information containing state information.

so signal 2 different button presses, on/off , fan speed, largely same, except on/off on/off bit(s) change, , fan speed fan speed bit(s) change. other information (temperature, cooling function, etc) transmitted according set on remote.

what means replace remote hardware of creation, need little more ir led , arduino. have reverse engineer remote protocol require oscilloscope (well, maybe not required make job easier) , chunk of free time.

i can offer suggestion though, enough i/o, rig button contacts on remote i/o pins on arduino , control there. keep in mind since have store states in variables in arduino sketch, , there no "syncing" between a/c , "remote" have built, important make sure code written such risk of "desynchronization" (i.e. arduino thinking has set temperature 65, when it's @ 68) minimal.

edit: ir frequency these units typically 38 khz, string length can vary typically longer average tv/dvd player remote. there many libraries available online tutorials decode ir signals simple ir receiver hooked arduino.

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