Control Methods: IR Vs Serial Vs IP

Virtually every device in a Smart Home will be controlled using one of these methods. What are they? How do they work? Which one should I choose?

IR

IR or infrared technology is the same stuff that’s in the television remote you use every day. Point it at the TV, press a button and a small LED flashes a sequence at the TV. A light sensitive receiver on the TV detects and decodes the signal. This is a very simple one-way method of control and for the most part is reliable.

Smart Home control systems often use IR emitters as a simple way to control devices. Issues ocure when devices share the same or similar codes. Also if a single output is used to control more than one device, the codes need to be timed so that each device is controlled in sequence. Emitters can look ugly when stuck to the the front of devices.

Serial

This is a way of sending simple commands and receiving responses from a device. Serial uses a cable connected directly between the device and controller. This is quite an old technology but is very reliable. Serial is not particularly fast, so can’t be used for images but for text feedback, such as volume, it’s perfect. Some control systems use a version of serial as their own communication method, Lutron bus and Crestron’s CresNet are prime examples of this.

IP

IP control uses a network connection to send the same or similar commands to serial control. The main difference is, as it uses a network, one processor connection can connect many devices and it is much faster.

So which one should I choose?

We don’t always get a choice, often we are limited to what the device is compatible with. When we do have the choice we should consider the pros and cons and pick what’s appropriate.

IR

Pros

  • Most common: The vast majority of products have IR control – best for compatibility.
  • IR learners are easy to find and cheap: So long as you have the remote you can get some control working.
  • Wiring is very simple: It’s basically a red LED that flashes so you only need two wires (cores).

Cons

  • Multiple IR’s on a single output can be problematic.
  • Devices can share codes: Undesired behaviour can happen.
  • Signals can be “blinded” by bright lights: If the device is in direct light it may not be able to “see” the IR flashing.
  • IR emitters look ugly.
  • Emitters have to be precisely located and, as they are stuck on, can fall off.
  • One way control: There can be no feedback so without being in view of the device we can’t be sure control has worked.

Serial

Pros

  • Directly connected to the processor/controller: No chance of missed commands or connectors falling off.
  • Includes simple feedback: Text can be received and displayed on graphic interfaces, making for a more immersive experience.
  • Feedback can be used to verify control has worked: much better for reliability.
  • Faster than IR.
  • Can work over long distances.
  • You can terminate your own cables.
  • No authentication required (though some products require a checksum)

Cons

  • Pretermitted cables are available but there are two options, straight through (normal), or crossed (null modem). It is not always clear which you need so can be trial and error.
  • Terminating your own cables can involve soldering which puts some people off.
  • If no pre-existing control module/coding exists for your control system it can be complicated to make your own.

IP

Pros

  • Fast and includes feedback: A lot of information can be sent quickly meaning cover art images or video streams can be displayed on graphic interfaces.
  • Feedback can be used to check control has been successful.
  • Easy to terminate your own cabling.
  • Pre-terminated cables are readily available.
  • A single cable can be up to 100m long, with the use of networking equipment, control can be sent over extreme distances.
  • A single controller/processor connection can control hundreds of devices.
  • Devices can be secured with authentication.

Cons

  • Control is reliant on a network connection: If the network has been poorly configured or goes down, control is lost.
  • Network firewalls can block control commands: even professionally configured networks can cause issues.
  • Devices often require specific setup for IP control to work correctly.
  • Control can be complicated: software or firmware updates can break control that has been working fine previously.
  • Devices can require authentication: If passwords get changed, control can break.
  • Some IP control requires Internet access: If Internet is lost, control breaks.
  • When Internet is required control can sometimes be slow or not work at all.
  • Control module programming is complicated so you will most likely need a professional to make one, if one doesn’t already exists. This can be costly and compatibility into the future cannot be guaranteed.

Conclusion

When IP control works and the modules have been well written it can be very simple to setup and so this is becoming the to go to option for a lot of devices. Yes IP can have serious reliability issues, but the ubiquity and cost of networking equipment also makes this a very cheap option.

Where possible and only when simple feedback is required, in my opinion, serial should be used. Anywhere else IP is best, so long as you are aware of the potential for future issues. IR is a last resort for compatibility purposes, though in some cases you may have no choice but to use IR.

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