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Topic: would you like a program challenge? (Read 2 times) previous topic - next topic

Henry_Best




the atmega 328 has 14 digital and 6 analog ports wouldn't this be enough?
I would just drive relays near the board and run the circuit from them.


That would depend on the voltage & current needed to light the signals, remembering that the 4-aspect signals can have two lights lit at the same time.

The second line says 'i would just drive relays near the board and run the circuit from them'  ?


That still doesn't tell me what voltage you're using. 240v AC would require expensive waterproof steel reinforced cable, if you're burying it. 12v DC, not so much, but you'll have to take into account the voltge drop over 200yds.

matelot

#26
Apr 04, 2013, 01:39 am Last Edit: Apr 04, 2013, 02:09 am by matelot Reason: 1




the atmega 328 has 14 digital and 6 analog ports wouldn't this be enough?
I would just drive relays near the board and run the circuit from them.


That would depend on the voltage & current needed to light the signals, remembering that the 4-aspect signals can have two lights lit at the same time.

The second line says 'i would just drive relays near the board and run the circuit from them'  ?


That still doesn't tell me what voltage you're using. 240v AC would require expensive waterproof steel reinforced cable, if you're burying it. 12v DC, not so much, but you'll have to take into account the voltge drop over 200yds.


Sorry Henry I don't want to sound unhelpful but the uno only needs to run relays or even opto isolators such as

http://www.ebay.co.uk/itm/280947061304

so the issue of power for the LED's is not important.
The whole circuit runs on 24 v dc but the board for the uno chip will have a 5v regulator , a 7805 , running it.
The present system is running the LED's at the moment but with boards in each signal box providing the correct switching. I want to run the circuit from a program chip and send just wires to each head.
That way I can also run an indication board at the signal box, Which I can't do at present.
I will take into account the voltage drop and change the inline resistors to adjust the brightness.
I do appreciate you keeping with me, thanks.


matelot


FYI, the analog ports of the UNO are analog only for input. They can be configured as digital I/O. See http://arduino.cc/forum/index.php?topic=22017.0


Thanks Sembazuru that is exactly what I wanted I now have 6 more ports.

Henry_Best


Sorry Henry I don't want to sound unhelpful but the uno only needs to run relays or even opto isolators such as

http://www.ebay.co.uk/itm/280947061304


Understood from earlier post.
Quote

so the issue of power for the LED's is not important.


This is the first time you've mentioned that the signals are LEDs, hence my confusion.


dc42


The whole circuit runs on 24 v dc but the board for the uno chip will have a 5v regulator , a 7805 , running it.
The present system is running the LED's at the moment but with boards in each signal box providing the correct switching. I want to run the circuit from a program chip and send just wires to each head.
That way I can also run an indication board at the signal box, Which I can't do at present.


Then I think the simplest solution is to run a separate Cat5e cable from the control unit to each signal. 100m reels of outdoor-use Cat5e cable are not very expensive. Each cable has 8 conductors, which is more than enough for 4 lights, 1 switch and ground (I suggest you use the 2 spare conductors as additional grounds). The final 2 signals have 5 lights and 1 switch between them, so you could manage with a single cable run for both.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.

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