Infrared Signaling and how it works.
IR remotes operate by modulating (turning on and off) an infra red (IR) light source. When the IR light source (the IR emitter) is "on" it is actually turning itself on and off thousands of times per second, too fast for the human eye to follow. The rate at which this occurs is called the carrier frequency. The terminology comes from the metaphor that the "carrier" carries the "information". This is done to provide a better transmission system and allow the overall IR system (transmitter and receiver) to operate in noisy (with respect to light) environments. It is important to understand that the IR receiver for a given remote is tuned to IR "carrier" frequency for that remote and will effectively not see IR signals sent on a different carrier frequency such as from other remotes. [Note: The human eye can never see an infrared transmission, so the concept of on and off is not with regards to visible light. Some equipment has a "telltale", a little red light that visibly flashes when the equipment receives IR signals. That is what we can see]
The "information" is placed on the "carrier" using several different techniques. The most common technique is Pulse Width Modulation. In Pulse Width Modulation the duration of the ON (carrier present, light flashing thousands of times per second), or Off (no light at all coming out of the IR emitter) periods is made to vary. Lets assume, because this is what is done, that we wish to send numbers representing what key has been pressed (and perhaps even what device this key is for). We first need to simplify the problem so that we don’t have deal with too many "Pulse widths". We can easily do this by representing the number in base 2, or binary. (I apologize if this now gets a little technical, but in reality it already has). In binary there are only two digits to worry about not ten as in decimal. Therefore we only need to have two distinct "pulse widths". If you think about it, the periods of on and off will need to alternate. If they didn’t it would be hard to judge their width. [Note: Other modulation schemes in particular RC5 do not use PWM. RC5 uses Phase modulation. Luckily for us we never have to decode or figure out the RC5 patterns because Philips has provided them as pure clean data. If you wish to know more about the RC-5 bi-phase method, read Guy Kuo's document.] Only one of the widths needs to vary. Either the width of the ON period or the Width of the Off period.
Hope this helps in a way.
So if i'm imagining the signal receiver in the roof of the car, you'd have a constant live with 2 switched lives, I imagine that a positive signal would be sent out to unlock the doors and same again down a different cable to lock the doors.
Get a multimeter to identify when the ceiling unit is down as to what cables go live when operating the doors
IR remotes operate by modulating (turning on and off) an infra red (IR) light source. When the IR light source (the IR emitter) is "on" it is actually turning itself on and off thousands of times per second, too fast for the human eye to follow. The rate at which this occurs is called the carrier frequency. The terminology comes from the metaphor that the "carrier" carries the "information". This is done to provide a better transmission system and allow the overall IR system (transmitter and receiver) to operate in noisy (with respect to light) environments. It is important to understand that the IR receiver for a given remote is tuned to IR "carrier" frequency for that remote and will effectively not see IR signals sent on a different carrier frequency such as from other remotes. [Note: The human eye can never see an infrared transmission, so the concept of on and off is not with regards to visible light. Some equipment has a "telltale", a little red light that visibly flashes when the equipment receives IR signals. That is what we can see]
The "information" is placed on the "carrier" using several different techniques. The most common technique is Pulse Width Modulation. In Pulse Width Modulation the duration of the ON (carrier present, light flashing thousands of times per second), or Off (no light at all coming out of the IR emitter) periods is made to vary. Lets assume, because this is what is done, that we wish to send numbers representing what key has been pressed (and perhaps even what device this key is for). We first need to simplify the problem so that we don’t have deal with too many "Pulse widths". We can easily do this by representing the number in base 2, or binary. (I apologize if this now gets a little technical, but in reality it already has). In binary there are only two digits to worry about not ten as in decimal. Therefore we only need to have two distinct "pulse widths". If you think about it, the periods of on and off will need to alternate. If they didn’t it would be hard to judge their width. [Note: Other modulation schemes in particular RC5 do not use PWM. RC5 uses Phase modulation. Luckily for us we never have to decode or figure out the RC5 patterns because Philips has provided them as pure clean data. If you wish to know more about the RC-5 bi-phase method, read Guy Kuo's document.] Only one of the widths needs to vary. Either the width of the ON period or the Width of the Off period.
Hope this helps in a way.
So if i'm imagining the signal receiver in the roof of the car, you'd have a constant live with 2 switched lives, I imagine that a positive signal would be sent out to unlock the doors and same again down a different cable to lock the doors.
Get a multimeter to identify when the ceiling unit is down as to what cables go live when operating the doors
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