Tow Posted March 8, 2011 Share Posted March 8, 2011 The topic says it all. In order to save wandering up to the top of a church hall and waving the remote at the ceiling, I wish to run RS232 over CAT5 cable from the project to the back of the hall. This is about a 20m run and I am wondering if the cable will lose too much of the signal to work. My gut feeling is that while it exceeds what some sources recommend as the maximum length for RS232, it should work? After all, it will only be used to send mainly on/off and change Input commands at 19,200 baud and not handle a continuous stream of data. The projector at the moment is an ageing 3M S50 and may soon to be replaced by a BenQ MX511. So if anyone has any control software for them I would be grateful, it has been almost 20 years since I have written software to control a serial port! BTW, I am open to other suggestions but this is zero (my pocket) budget project, so RS232 to LAN converters or better still a 'proper' projector etc are out of the question, unless they can be sourced cheap from China on ebay! Link to comment Share on other sites More sharing options...
Brian Posted March 8, 2011 Share Posted March 8, 2011 The issue is one of capacitance. RS232 has a limit of 2500pF; with normal RS232 cable it tops out in the 15-20m range. However, if you use a low capacitance cable you can get away with longer runs. Some CAT5 cable will be down around 70pf/m giving you a 35m run. Link to comment Share on other sites More sharing options...
Paul TC Posted March 8, 2011 Share Posted March 8, 2011 Some CAT5 cable will be down around 70pf/m giving you a 35m run.I have in past used RS-232 (@9600 baud mainly, with some @19 2000)over 30 m of cat 5, including a section of multipair in risers to patch panels in a building with no issues, between PC's, Terminals, Serial Printers and Data Switches. We used a pair of wires for tx and a pair for rx and commoned one side at each end in the RJ-45 to 9 or 25 pin D adapters we used to hook up to a RJ -45 fly lead from the wall box. Other wires were used as required for control lines, CTS, RTS, DCD & DTR. Link to comment Share on other sites More sharing options...
Ian H Posted March 8, 2011 Share Posted March 8, 2011 Rs232 will work over 150mts ---- Had to re color balance a Versatile LED screen in a Baseball stadium last year used every 9 pin cable we could find and every joiner we could fine and it worked just dandy... Link to comment Share on other sites More sharing options...
Tow Posted March 8, 2011 Author Share Posted March 8, 2011 Thanks for the info. I would have connected the spare wires from the RX and TX twisted pairs to ground. Some thing like this :http://www.jneuhaus.com/serial/pc9.png Link to comment Share on other sites More sharing options...
timsabre Posted March 8, 2011 Share Posted March 8, 2011 I wouldn't do that as it will make the capacitance worse. 20 metres is nothing though, it should work fine whatever you do. Link to comment Share on other sites More sharing options...
AHYoung Posted March 8, 2011 Share Posted March 8, 2011 we run rs232 projector controls down 3pin data cable, im sure its run down 100m multis with various other lengths plugged in and never had any problems, most units are 9600 or 19200 baud which is pretty low bandwith. to control the unit you just need pin 2rx and 5 {gnd} connected, but as its 3 pin / core id connect pin 3 TX as well in case you need the feedback. also never encountered any problems having the rx and tx twisted together... Id lookout for a used Procon or Amx button panel as these are programmable devices that will send the commands needed ie on/off, blank, input select and avoids the need for a pc and any capers.... another solution might be to use a "magic Eye" these are designed to change your sky box in the living room from your bedroom, and the ir signal is sent down a length of rf cable, its effectively just a ir reciever and transmitter with a bit of cable in between, I just googled it and the going rate seems to be 4 quid. no idea whether it will work, but no reason to assume it wont, and its only the price of a pint wasted. if it doesnt. Link to comment Share on other sites More sharing options...
dbuckley Posted March 8, 2011 Share Posted March 8, 2011 Yes, I'm in the naughty club too, I run RS232 to projecors over hundreds of feet of standard mic cable, with a XLR to 9 pin D converter at each end. Though when I say "projector", I of course mean Kodak Ektagraphics (Carousel AVs in the UK I think) :) Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.