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Hi I am a construction site manager with very little knowledge in electronics. I have recently invented a new site safety device which involves the use of multiple transmitters and receivers. I purchased the transmitter and receiver relay sets on line (433Mhz). The receivers have been individually coded by a solder link. The problem I have is when I transmit more than one signal at the same time the units act irrationally turning on and off. Why does this happen and can it be prevented? Any help would be greatly appreciated as the success of the product relies on the system working without interference.

john fitzsimmons
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    Welcome to EE.SE, John, but even as a first time poster don't you think part numbers and links to datasheets would be part of the minimum information required to answer your question? Add it to the original question rather than in the comments. – Transistor Apr 18 '16 at 22:10
  • It's called "data collision" and is avoided by protocol designs that are aptly named "collision avoidance systems". They do however require a lot more sophistication so please sketch out what your system looks like and specify transmission repetition rates etc.. – Andy aka Apr 18 '16 at 22:18

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Although you say you have individually coded the devices it appears that you are trying to use multiple transmitters on the same channel or else the receivers can't discriminate between adjacent channels. Without datasheets this is anyone's guess.

Of more concern is that you are using these as a "safety device". Be aware that your system needs to fail in a safe manner. i.e., if anything goes wrong, including flat battery, interference, breakdown, etc., that the output is guaranteed to shut down. Wireless safety devices are used in industry but you will find that the design is quite complex.

Transistor
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Welcome, John, but it would help to know what devices you are using.

Having said that, I know of no 433MHz transmitters that are designed to play nicely with other 433MHz transmitters. There just isn't a wireless protocol defined for that at 433MHz. The transmitters will interfere with each other anytime more than one tries to transmit at the same time, and it sounds like the receivers aren't designed to handle that very nicely.

What you need is a wireless system which allows for multiple transmitters. ZigBee is the first one that comes to mind, but there are others. A lot depends on the range you need.

Mark
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