Cheap RS485 to 9 Serial pinout.

[a31ford]

Greetings ALL.

 

I've got one of those generic DB-9 to RJ-45 "Terminal" connectors. It has all 8 of the RJ side populated, and 7 of the DB-9 (2 wires from the RJ go to the same pin on the DB.

 

IT SHOULD work, for the 100 feet or less option, (shown as the connector on the left, page 22 of the CTB-16PC DIY solder kit manual).

 

Does anyone have the pinout of the LOR version of this adaptor ?

 

AND, are the RJ-45 cables "standard straight through" wiring or "cross-over style" ?

 

Thanks in advance,

 

Greg Manning

 

 

[Don]

Been a long time since I've answered this question. If memory serves there are some electronics inside the DB9 connector that convert over to the RS485 protocol. That said, a regular DB9 converter won't work. Much better of getting one direct from Light-O-Rama.

 

The CAT5/6 cables are straight through.

[a31ford]

So.......

 

With A little investigative work, I've found this out, the small 8 pin IC on the SB16-PC LOR board is INDEED an RS-485 transceiver (Chip marked 65HVD3082) it's good to minus 40 C (that's good for where I live). 

 

And the following in the Cat5 cable into (or out of) the board, the RJ 45 connector is as follows, pin 3 is VCC (+9), pin 4 is "A" of the RS485 network, pin 5 is "B" , and pin 6 is ground (using the RJ-45 pinout).

 

Technically all one needs is the 3 wires "A", "B", and ground, HOWEVER, the VCC is needed for OTHER LOR functions.

 

I will ONLY be using the SB16-PC type boards at this time, so using 3 wire shielded cable is ok, in MY application.

 

As far as the RS-485 adaptor, I had some success, BUT it's NOT consistent at controlling the board, so I'm going to have to wait for the 485 adaptor I've ordered from LOR

 

I'm itching to see my first board working, (still got 3 more to assemble)......

 

Greg

[ErnieHorning]

The generic DB-9 to RJ-45 is not necessarily very reliable depending on the RS232 port they’re plugged in to.  If it’s one that requires no external power supply, it has to derive it from the RS232 port.  The RS232 port may not supply enough current to power anything because that’s not what it was intended to do.  USB would be a much better choice, even if you had to add a card.
 

Technically all one needs is the 3 wires "A", "B", and ground, HOWEVER, the VCC is needed for OTHER LOR functions.

 

Technically you only need 2 wires, "A", "B".  Ground is not actually needed. 

 

The type cable you use can also make a big difference, especially over long distances.  There’s a reason that most people are using CAT5 and not just because it’s cheap.  Capacitance can snub the data signal and wrapping braided wire around another one will do so.  I’m not saying your wire is bad but if it still doesn’t work, the wire or the RS232 port could be the problem.  CAT5 has very low capacitance and goes for thousands of feet.

[a31ford]

BTW Don, Thank you for the first reply.

 

Ernie, Actually ground IS required, the A & B are floating and can go + or - with reference to Ground,(Earth), the fact that many people use 485 without one, doesn't make it right, IN fact, with a ground, ( and shielded  2 pair (Belden 8723 or Equ.)) one can get the 7000 ft total length quite easy (and the 120 ohm resistors at each end), with NO repeaters.

 

Try doing that in a plant that has 20 some odd terminals in amongst heavy electrical motors  on a 300,000 sq ft assembly line.

 

Ground is a good thing (it also helps in protecting from EMF surges also).

 

But, for the most part, many of these systems don't even get close to 150 feet away from the director, so I see why many don't use it.

 

Greg 

[a31ford]

Actually I'm going to add a bit to my last post.

 

 Ernie is somewhat correct, and here is the reason why, Today's house electrical, (120/240)is grounded in the first place, IF (key word IF), IF you are using a 3 wire cord on the right side of any of your 16 channel controlers, this will provide a "FLOATING" ground (by virtue of the controlers power supply being pseudo grounded through the EMF of the transformers neutral side.

 

Here's the thing about this...... IF your show goes "wonky" every now and then, try adding the correct ground on the RS485 cable (LOR includes the ground on the circuit board, it's just a matter of using the correct cable between equipment).

 

Myself, Since I'm so ANAL about serial communications stuff,  I'm going to be using 2 pair, individually shielded (Belden 8723) cable for communications, AND using the proper 120 ohm resistors between 'A" & "B", at each end of the entire link.

 

See, I have a total run of 1450 feet of Comm cable, AND a couple of heavy motors near the area (well pump, and sewage pump).

 

Greg

[ClydeL]

Thanks for asking this question Greg.  Was going to run a small setup in the back yard and wanted a cheep RS-485 connector and found the parts to make it on Monoprice.  I don't have a stand alone unit and I do have an extra computer with the S2 software loaded.  Soooo, using this home-made assembled RS-485 should work for 2 controllers (max 3) at a distance of no more then 20' right? 

Was considering a new one during the summer sale but the shipping cost added to the sale price of the cheep RS-485 dongle is 15.00 to ship from NY to PA.  I can make one for the cost of shipping.

[Steven]

RS-485 (used by the LOR network as well as DMX and industrial uses such as factory automation) is a 3-wire protocol. The reason the 3rd wire (signal ground) is needed is because the voltage on the A & B signal lines are between 0 and 5 volts, and if ground is not connected, the voltage on both lines could drift to above 5 or below 0, which may saturate the receiver, which will prevent it from distinguishing the levels between the lines.

 

In contrast, 10baseT (Ethernet) uses 2-wire differential signaling, which does not require a ground. It does, however require a transformer in both the transmitter and receiver, which limits it to point-to-point use, and also adds weight and cost.

 

RS-232 (as present in the DB-9 connector on many computers) uses non-differential signalling, using a ground and voltages that go from -12 to +12v. Connecting an RS-232 line to a RS-485 network can work, but can be very unreliable, and could possibly damage the receiver, because the voltages exceed the 0-5 volt range of RS-485.

[Ken Benedict]

IMHO, it seems like a lot of very talented people are spending a lot of time trying to save $30 plus postage on a DIY device that runs the risk of damaging much more expensive controllers attached to the network line.

 

It could release the Magic Smoke that is needed to run your shows.

 

Repair costs could easily exceed the cost of the LOR version of the RS485 Converter.

 

But then you would have excellent hindsight.

 

Is it worth the risk?

[Steven]

IMHO, it seems like a lot of very talented people are spending a lot of time trying to save $30 plus postage on a DIY device that runs the risk of damaging much more expensive controllers attached to the network line.

 

This is a hobby, and IMHO, learning through experimentation is an important part of a hobby. The knowledge you gain by taking things apart and figuring out how they work is very valuable, and some may say is even more valuable than the cost of repairing something.

 

In this instance, the only possible damage that could come to the controller by driving the RS-485 receiver with excessive voltages is the RS-485 transceiver chip itself, which costs about $5 at the local electronics store. (It's also possible to damage the voltage regulator for the accessory power by keeping it shorted for an extended time. This part costs less than a dollar, and isn't even needed if you don't use an SC485, ELL, Input Pup, Network Repeater, or PIR Motion Detector.)

[Ken Benedict]

This is a hobby, and IMHO, learning through experimentation is an important part of a hobby. The knowledge you gain by taking things apart and figuring out how they work is very valuable, and some may say is even more valuable than the cost of repairing something.

 

In this instance, the only possible damage that could come to the controller by driving the RS-485 receiver with excessive voltages is the RS-485 transceiver chip itself, which costs about $5 at the local electronics store. (It's also possible to damage the voltage regulator for the accessory power by keeping it shorted for an extended time. This part costs less than a dollar, and isn't even needed if you don't use an SC485, ELL, Input Pup, Network Repeater, or PIR Motion Detector.)

+1

Edited July 16, 2013 by Ken Benedict

[ErnieHorning]

RS-485 (used by the LOR network as well as DMX and industrial uses such as factory automation) is a 3-wire protocol.

RS-485 is a standard, not a protocol but that's nitpicking.

 

The reason the 3rd wire (signal ground) is needed is because the voltage on the A & B signal lines are between 0 and 5 volts, and if ground is not connected, the voltage on both lines could drift to above 5 or below 0, which may saturate the receiver, which will prevent it from distinguishing the levels between the lines.

 

With respect to what?  If you don’t supply a return path, there is no potential difference.  Each controller can have its own virtual ground and easily operate with another one.  Sure if the voltage was high enough, you could have an inductive or capacitive coupling to earth ground but then you’d have other issues too.  I don’t see it as a problem.

 

I see more of an issue in adding the ground on a long run because now you can have a common-mode noise between the ground wire and each individual input wire, nullifying the whole advantage of a differential input.

 

If you’re blowing out a 485 chip, it’s more likely that this is happening because you’re operating in the rain and you had water conduction that by-passed one or more opto-couplers.

[a31ford]

HI Ernie, (List).

 

Ernie, the only reason for using a ground in RS485, is for the Shield, on long runs, (using foil or braid say 22/2 or 18/4 "twin shield", much of the work I do (Did) was using RS 485, on industrial networks, prior to cat 5 and tcp/ip.

 

Put it this way.... I'm one of the few people that owns a DB25 AND a DB 9, breakout box. (GAWD, am I THAT old ????)

 

300 baud, NO, sorry, 150 Baud, HANDSET set coupled modems..... still have a pair some where.

 

I sent this to zeighty the other evening.....

 

Here's a "BLAST FROM THE PAST", out of my personal library.....

 

 

Greg Manning

[ErnieHorning]

... the only reason for using a ground in RS485, is for the Shield, on long runs, (using foil or braid say 22/2 or 18/4 "twin shield", much of the work I do (Did) was using RS 485, on industrial networks, prior to cat 5 and tcp/ip.

.

 

I have no issue with a shield as long as it’s connected only at the source end but not both.

 

I checked around at work and our production controllers do not use ground, only a shield.  One controller that’s 400 feet from the computer is double shielded, but again only on the computer end.

 

... I'm one of the few people that owns a DB25 AND a DB 9, breakout box. (GAWD, am I THAT old ????)

 

300 baud, NO, sorry, 150 Baud, HANDSET set coupled modems..... still have a pair some where.

 

Here's a "BLAST FROM THE PAST", out of my personal library.....

 

I’m also one that has both DB25 and DB9 breakout boxes, though I haven’t used either for quite a while.  I also remember when The connector was correctly called a DE9.

 

I don’t own one but I did use a HANDSET set coupled modem.  I used a couple of telephone books to press the handset in tight; a square peg in a round hole kind of thing.

 

I believe I still have that book around here somewhere.  I also have two or three circuit design cook books from the same era.

 

Yeah, I’m afraid I’m older that dirt too.

[a31ford]

GAWD... "Older than Dirt", tooooo Funny !

 

I have to remember that one Ernie........

 

Greg