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<p><b>New page</b></p><div>= RS-485 =<br />
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'''RS-485''' is an electrical communication standard designed for reliable data transmission over long distances in electrically noisy environments.<br />
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Unlike protocols such as [[DMX]] or [[Renard]], RS-485 defines only the electrical characteristics of the communication interface. It does not define the format of the transmitted data.<br />
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RS-485 has been widely used for industrial automation, building control systems, and animated Christmas lighting for many years.<br />
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== Why Use RS-485? ==<br />
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RS-485 offers several advantages over single-ended serial communication:<br />
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* Long cable lengths<br />
* Excellent noise immunity<br />
* Reliable operation in outdoor environments<br />
* Supports multiple devices on one communication bus<br />
* Low installation cost<br />
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These characteristics make RS-485 ideal for Christmas lighting displays where controllers may be located hundreds of feet from the show computer.<br />
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== Differential Signaling ==<br />
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RS-485 uses '''differential signaling'''.<br />
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Instead of transmitting data on a single wire referenced to ground, the transmitter drives two wires with opposite voltages.<br />
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The receiving device detects the voltage difference between the wires rather than the voltage on either wire individually.<br />
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This greatly reduces susceptibility to electrical noise.<br />
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== Typical Wiring ==<br />
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Most RS-485 systems use:<br />
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* One twisted pair for data (A and B)<br />
* Optional signal ground<br />
* Shielded cable when required<br />
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Twisted-pair cable helps cancel electrical interference and improve communication reliability.<br />
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== Common Applications ==<br />
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RS-485 is used by many communication protocols, including:<br />
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* [[DMX]]<br />
* [[Renard]]<br />
* Modbus<br />
* BACnet<br />
* Industrial automation equipment<br />
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Although these systems all use RS-485 hardware, they are not directly compatible because each protocol defines its own communication format.<br />
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== RS-485 vs. Ethernet ==<br />
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{| class="wikitable"<br />
! RS-485<br />
! Ethernet<br />
|-<br />
| Serial communication<br />
| Packet-based networking<br />
|-<br />
| Differential signaling<br />
| Differential signaling<br />
|-<br />
| Multi-drop bus<br />
| Switched network<br />
|-<br />
| Excellent for controller communications<br />
| Excellent for computer networking<br />
|}<br />
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== Advantages ==<br />
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* Long communication distances<br />
* High noise immunity<br />
* Low-cost wiring<br />
* Supports multiple devices<br />
* Proven industrial reliability<br />
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== Limitations ==<br />
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* Lower data rates than Ethernet<br />
* Not compatible with Ethernet equipment<br />
* Requires compatible communication protocols<br />
* Bus wiring must follow recommended termination practices<br />
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== Christmas Lighting Applications ==<br />
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RS-485 is commonly found in:<br />
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* [[Renard]] controllers<br />
* [[DMX]] lighting equipment<br />
* Some commercial lighting controllers<br />
* Legacy Christmas lighting hardware<br />
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Although modern smart pixel systems often use Ethernet or Wi-Fi, RS-485 remains widely used for AC lighting control and DMX-based equipment.<br />
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== Related Articles ==<br />
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* [[DMX]]<br />
* [[Renard]]<br />
* [[Differential Receivers]]<br />
* [[Pixel Controllers]]</div>ErnieHorning