Vista Pd 485 Distance ?

[JLA]

Hi,

Does anyone know the suggested / safe / sensible distance limits for the 485 connnection on a Vista Powerdome, in belden, controlled via a DM -SD.

Thanks in advance,

J

[james.wilson]

485 is designed for 1km

[arfur mo]

485 is designed for 1km

correct, but at 2400 baud, higher the baud shorter the distance

regs

alan

[james.wilson]

good call see you do learn something new every day, i thought 1km was at 1200 Baud

[SUBS]

good call see you do learn something new every day, i thought 1km was at 1200 Baud

]

If you Google rs485, most sites say 4000ft, wouldnt be too keen on risking it meself though.

presumably it depends on the cable specs.

I have several sites - took jobs over, cabled by someone else's subbies. - with both rs485 and duplex rs 422 on ordinary 6 core alarm cable, runs of 300M, star wired, not daisy chained, had to use a dis amp to get the duplex 422 perfect, but the 485 works ok. not reccomeded though. Also have seen rs485 telemetry on cat5 where the pairs have been doubled up, ie ora+ ora/whi together & bu+bu/whi together (probably trying to reduce volts drop) also working fine. over quite large distances. so it looks like in practice, you can get away with pretty much anything.

Prefer not to have the worry personally, at least with the right stuff you know it should work

[sjonley]

RS485 is good for 1km like alan says. I have seen domes working upto 1km on 9600 baud rate and 1.5km on 2400 baud. Response times on 2400 baud is slower than 9600 ie pan left then quickly pan right might not seem to respond on 2400.

I would not recommend anything other than UTP for RS485 transmission. The twists in the UTP are there to eliminate inteference.

[SUBS]

RS485 is good for 1km like alan says. I have seen domes working upto 1km on 9600 baud rate and 1.5km on 2400 baud. Response times on 2400 baud is slower than 9600 ie pan left then quickly pan right might not seem to respond on 2400.

I would not recommend anything other than UTP for RS485 transmission. The twists in the UTP are there to eliminate inteference.

I wasnt reccomending using the wrong cable, just pointing out that at a pinch, you can 'get away with' quite a lot. IMO cat5 is often chosen due to the price, where its unsuitable, Where a better spec ie, lower capacitance per metre, or foil screened, or stranded cable would be better, or is reccomended.

As a subcontractor, I have been asked to use it for all sorts of things, like lock supplies, Pac readers, etc even once for a PIR and have politely declined, several times. A year or so down the line, everyone will forget who spec'd it, and blames the engineer who fitted it !

[arfur mo]

imo if you step outside the recommended stats you may well get away with it 5 out of 6, but on one site interference sources may well ruin your day,

pays yer money takes yer risk - and on the chin if not lucky

regs

alan

[james.wilson]

agreed

[ispy]

1500 mts no probs but remember if using more than 1 dome daisy chain with EOL or use 485 line extenders (hubs) BBV do them. thats the safest bet i've done loads of jobs like this and never had a problem.