New project question

[SteveyD]

Here's a question regarding a new project presented to me today.

1. A master control until that with the press of a specific button will light up a small light on multiple display boards up to 2 miles away.

So taking a simple push button input, it will light up a specific light. and carry that light turn on command to multiple display units as far away as 2 miles.

Input button 1 will light up all "light 1" displays in the chain,
Unput button 2 will light up all "light 2" displays in the chain,
etc etc, to light 5.

Or think of a Campus complex that with a single command unit in the main office that will light up a red,green,blue,yellow or orange LED/light at every exit door of every building on that Campus.

No other light can be lit other than the master command selected one.

Each remote display board has its own local power supply so only a signal needs to be sent.

Now a simple LED or Blinky routine will handle the button/light selection process. What I am looking for is a way to transmit the light selection command to the remote units along a long distance hardline like a cat 5 cable, and through a relay or a remote PIC have it light the correct display light.

This will not require a lot of power at the remote displays if an LED and uC are used, 5volts.

Just dont know how at this point to impliment the carrier commands over such a long distance.

Any suggestions?

 

[picasm]

You could use DTMF tones, a quick google search will find many microcontroller projects for it.

Alternatively, if you already have network connections near each panel, there are tcp/ip Ethernet modules available intended for applications such as remote home automation, monitoring etc. that could be used.

 

[SteveyD]

Yes, there are Network drop boxes at each location, thats what gave me th thought of using Cat5 to carry the signal as most of the doors involved already have the cable passing close by.

I'll check out the Tones.

Thanks

 

[ericgibbs]

Yes, there are Network drop boxes at each location, thats what gave me th thought of using Cat5 to carry the signal as most of the doors involved already have the cable passing close by.

I'll check out the Tones.

Thanks

hi,
Look at this PIC application note for Tones.

 

[SteveyD]

Perhaps I'm over complicating this project a bit.

I'll try to explain better, the longer I've had to think about this, the more I think a uC may not be required at all. Although using a uC would still be fun.

1. Take 5 lights, and 5 buttons in a single project box.

2. A single light is tied to a single button.

3. Only one button can be held down at any given time, the other 4 are released. The light corresponding to that button is then illuminated.

4. Now take 5 more lights in a separate project box, and wire them to match the lights in the first box.

5. Step 4 would be repeated as many times as required.

I was thinking each remote box would have its own power supply, but is it needed if I push 12V or greater down the lines?

Would 12vdc carry over the estimated distance of 2miles(max) to light up the LED? or would it be better to add a uC in each remote box to pick up the signal or the button press itself and control its own light bank?

 

[SteveyD]

Doing a bit more research on this, they only want 4 lights so the attached link shows a circuit very close to what should work.

**broken link removed**

Adding some 2n3904's between the Q1,Q2 1K resistors and the LED's would allow for power to be supplied to the LED's at the remote location.

Given the distances involved and the multiple remote display led's to be driven, I still am stuck on how to boost the output of Q1,Q2.

Other than using tones generated from a uC, is there another way to bridge the signal distances?

 

[Pommie]

To overcome the cable length you could use a constant current source and a higher voltage supply. By using a constant current source on the return connection you would only need one per remote location. If you also use PNP transistors to switch a 12V supply you would only need one transistor per output. Cat5 has a resistance of approximately 10Ω per 100M and so 2kM would be around 200Ω or 400Ω when you include the return connection. This means that at LED currents this is easily achievable with 12V.

Mike.