![]() Now that you know what not to do, how do you do it correctly? Don't ever put power current for your lights onto the signal ground. Again the result is the data into the receiver has a big voltage offset from true ground from the transmitter resulting in maximum chip ratings being exceeded and blown chips. Running power current makes both ends of the signal ground be different voltages. The signal ground should NEVER be a power ground. 2 are live signals the data and the inverse of the data. As we all know, voltage is lost along the length of a data cable. Power on the Data Cable is error number 2. ![]() The SHIELD or the Ground in the data cable MUST be connected at both ends. A chip receiver without a common ground reference with the transmitter can easily exceed maximum input voltages in reference to the minus power pin and result in toasted chips. My advice is to read the data sheet for the maximum values on the transceiver chips. This part is true and sometimes without a shield connection, it works. A receiver chip is expecting 2 inputs to be differential. This is entirely against the spec and an easy way to blow chips. Understanding the standard is a requirement to get it right.Įrror #1 commonly seen and mentioned. The RS485 standard was written to address issues with long haul data transmission to engineer problems out. I'm going to get technical for the rest of the DIY people. I know not everyone here is really technical so the guru's bear with me. I have NEVER replaced a blown transceiver chip. This post is to protect your transceiver chips. In addition I have seen some posts where some think Isolate means no ground wire. Sorry to bump an almost year old thread, but I didn't see any solid answers on the blown chip issues. For instance RPM's and RJ's DMX dongles both have isolation in them but you typically only have one or two of them. With that said - if the interface is used to drive a large number of display items, then the cost can be absorbed. Putting in fully isolated interfaces adds a fair amount of cost to a controller - it's doable but not sure the cost benefits are there - at least for Renards. ![]() Even if the RS485 chip does blow - big deal - you're out a buck or two at most. There must be thousands of Renards alone so the data tends to suggest it's not a big issue. I guess you could plugin a dc board by mistake into the input but still.Įxactly right - been on the board a while and I haven't seen too many cases of folks blowing up their RS485 interfaces (I'm discounting those that put the chip in backwards, etc) while running in the yard. The supply is also floating so the only way to blow up more than just the chip. Unless it was useing a starconfiguration vs daisychain. Well to be far the ren stuff would make it hard to kill more that once controler. ![]()
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