Remote serial LCD display?

$WMc%

Hello All

I need to send serial data from a BS2·to a Parallax serial LCD that is about 1600 feet away from the BS2.I have 4 existing spare wires (12GA) that I can use.

The BS2 is located at the front gate, It controls the gate operation and a keypad for employee access along with a serial LCD so the employee can see that they have pressed the correct keys on the keypad.

My Chief Engineer has requested a LCD display in the control room that will display the same data seen at the front gate.

My Question is how to amplify a serial signal to travel a long distance (1588feet) with as few parts as passable?

I feel any answers to this would be beneficial to all BS2 users

Thanks in Advance

________$WMc%____

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The Truth is out there············································ BoogerWoods, FL. USA

Prettybird

Check out the LM311 comparitor chip. You can input 5 volts or less, set a reference switch level and go up to 15v on a single power supply. It can handle high frequencys. It can also handle 100ma easily.

TinkersALot

If your data rate is low-speed, then you could consider RS-422 driver/receivers to provide the physical layer between these two end points. Hope that helps.

Phil Pilgrim (PhiPi)

I second the RS422 idea. It's both simple and reliable. I've had excellent luck with the LTC490 transceiver.

-Phil

Prettybird

Line drivers and recievers are good too, but wonder about the 5v drop in a long run. Use to industrial situations in the past. That is why most DC control is 24vdc. Have to experiment. If your wire is in conduit underground, no need to worry about noise. Use to use line drivers and recievers for encoders but not 1,600".

stamptrol

A 75176 chip on each end will give you a good, solid differential signal out to about 400 feet. I use them extensively in rs-485 multi-drop communications.

Cheers,

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Tom Sisk

http://www.siskconsult.com
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$WMc%

Thanks to all for the relpys

I'll research Your suggestions.

The RS422/485 did get Me to thinking about a -12volt/+12volt setup, since I already have a 24volt transformer with a center tap.The RS422/485 transceiver might do this for Me?

____Thanks Again_________$WMc%_______

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The Truth is out there············································ BoogerWoods, FL. USA

stamptrol

The 75176 chips do it all without need for dual supplies. It switches the A - B outputs from 0 to 5 volts, alternately to give the differential signal.

Cheers,

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Tom Sisk

http://www.siskconsult.com
·

$WMc%

Hello All

I downloaded the data sheets for the SN75176, But I really couldn't determine a circuit configuration to use it.I have never used this chip before so its all new to Me. Do I need two of these 75176,one at each end? Do You have a generic circuit for a similar use with this chip as mine?

I also downloaded the data sheets for the LM311, This looks promising as well but I have never used this chip either. I was hoping for some generic example circuits in the data sheets, but I really didn't see anything that applied to My project.

Any additional toughts or Ideas·would be great!

___ThankAgain___________$WMc%______

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The Truth is out there············································ BoogerWoods, FL. USA

Phil Pilgrim (PhiPi)

Steer clear of the LM311 idea. One big advantage of using a tranceiver designed for RS422 is that the input common mode range extends beyond the supply rails. You won't get that from an op amp without additional external circuitry. The SN75176, BTW, is a rather old bipolar part and draws a lot of current. Moreover, it's RS485 (2-wire half-duplex) vs. RS422 (4-wire full-duplex). IOW, if you've got four wires, you might as well use them. The LTC490, OTOH, is CMOS (full-duplex). You can reduce the current requirements even more by using a capacitively-coupled termination network. The LTC490 datasheet explains how.

-Phil

stamptrol

Pick up a copy of Jan Axelson's book "Serial Port Complete" for everything (theory, schematics, sample program) you'll ever need to know about serial communication.

The 75176 is an older chip and continues to be used simply because it does a great job. Also has variations with built-in overvoltage protection. Look it up on DigiKey.
The LTC490 or LTC491 will also work.

Cheers

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Tom Sisk

http://www.siskconsult.com
·

$WMc%

Thanks Phil Pi

The LTC490 is just what I was looking for. The example circuits are great too.These examples I can·understand.

Thanks Again

_____$WMc%______

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The Truth is out there············································ BoogerWoods, FL. USA

$WMc%

Thanks Stamptrol

I'll check out Jan Axelson's Book.

I deal with serial communications all day at work. I understand most of the protocols but I haven't really dealt with the hardware that makes all this happen. The book sounds like a good read.

Thanks Again________$WMc%________

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The Truth is out there············································ BoogerWoods, FL. USA