IR Remote Decoder Egr 326H Doug Carlin How IR works • IR is an invisible light that can transmit large amounts of information while preserving the uniqueness of each bit. Remote Encoding Scheme Each Remote Uses an Encoding Scheme Since I chose a Sony remote, its scheme is using the pulse-width coded standard. Sony uses a 12-bit protocol that consists of a 4-bit ID code 4- bit command code followed by 3 bits to sync the data. “1) Pulse-Width-Coded Signals vary the length of pulses to code the information. In this case if the pulse width is short (approximately 550us) it corresponds to a logical zero or a low. If the pulse width is long (approximately 2200us) it corresponds to a logical one or a high. “ Source http://www.ee.washington.edu/conselec/A95/projects/pierreg/main.ht m Objective To study the signals emitted from a Sony remote control and create an interfacing device with the PC. The extension of this project being researched is a possible source for controlling household electronics through the web. Motivation • With all remotes on the market (not to mention in the households it only makes sense to understand whether or not you actually need these advanced remotes or if you can replicate them. But how can you encode data that you cannot “see”. That is where the IR Remote Decoder comes • This project attempted to “see” the encoded data from a single remote and translate that back to what button/key was pressed (for under $50.00). • This may be used in the future to have a computer pc program to transmit the “button/key” to a device via a range extender possibly through the internet. Basic Design Diagram Pic Power Power Supply Supply Plug Serial PC (Wall RS232 Interface Transformer) On/Off Power Switch Infrared Detector Infrared LED Parts to Produce a Working Circuit Software Implementation Start Routine Clear Memory Display Ready Signal END Wait for no Signal signa Store Timing groups of 8 Subroutine bits into a table Initalize Timer while n<9 Store Start Timer Shifted Result Look for Set pulse Counter transitions Shift bits/ Stop Timer store timer info The Source of Error Reasons it was picked: • This transformer output is 9 Volts DC at 500mA. The voltage regulator used is a voltage regulator with a dropout voltage of 2 Volts. Therefore a voltage of at least 7 Volts from the transformer must be used for the regulator to operate properly. The closer to 7 Volts the less differential voltage, thus less power lost as heat. • Unfortunately the transformer put out 14 V and the circuitry was not able to handle the power dissipation.
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