Controlling colour light signals with R8247 and Elite

[idlemarvel]

I have configured an R8247 to give continous output, but when I test the output with a voltmeter it seems to provide -12v DC rather than the +12v I was expecting. This was confirmed when I tried to power a Traintronics two aspect signal (which expects

+12v). I can only get it to turn on a light if I reverse the wires. (This is connecting the wires directly not through the supplied Traintroics circuit board.) This would be okay except the red and green lights have a common return, so effectively I can only

operate the red or the green. Is the R8247 working as expected? Has anyone got R8247 working with Traintronics signals? Is there a CV setting to change the output of the R8247 to +12v? I would be pleased to hear from anyone. Thanks.

[ace10086]

It's not something that I have checked but if the 8247 does have the +ve voltage on the common and switched ground then there isn't anything you can do to reverse it.

I assume it isn't possible to rewire the lights?

[idlemarvel]

Thanks ace, unfortunately it is not possible to rewire the lights

[tsclass87]

idlemarvel said:

Thanks ace, unfortunately it is not possible to rewire the lights

the traintronics need their own decder to operate correcttly with the elite (a TT301).
however,although this works it is not a straight forward

as a single click to change the lights.
currently, I have to double click the control button as if turning each colour led on then off.
this does not help when using railmaster as your icons never match the colour signal on the layout.
have queries

with the manufacturer and hornby care on how to get around this problem.

[poliss]

Swap the leads round on your voltmeter and I bet you'll get a reading of +12v.
I recommend getting a copy of Digital Command Control by Ian Morton which shows how to wire signals to an accessory decoder.

[idlemarvel]

poliss said:

Swap the leads round on your voltmeter and I bet you'll get a reading of +12v.
I recommend getting a copy of Digital Command Control by Ian Morton which shows how to wire signals to an accessory decoder.

I think

if I swapped the leads and didn't get the reverse reading I'd be worried that someone had changed the laws of physics while I wasn't looking :-)

I have the excellent book you reference poliss but it doesn't cover this situation. It would appear that

with the R8247 and I believe other accessory controllers the common (black) is +12v and the red and green are ground. As the Traintronics signals use LEDs it is necessary to have the polarity correct. They expect common ground and +12v on the switched connections.

And is it not possible to switch the wires at the signal end because the red and green lights share a common lead. Net result is that you can turn red and green on and off but only at the same time! I need to reverse the polarity of the output from the accessory

controller somehow. I'm sure that's possible with some simple circuitry but I wasn't expecting to have to do this.

[Rog RJ]

Probably easiest to use the decoder to drive a couple of relays, or you could probably use a single latching relay if you are only using two aspect signals?

[Flashbang]

Hi
If its any help the basic wiring from an accessory decoder is shown here....
http://www.brian-lambert.co.uk/DCC.htm#Accessory%20Decoder.

[idlemarvel]

Flashbang said:

Hi
If its any help the basic wiring from an accessory decoder is shown here....
http://www.brian-lambert.co.uk/DCC.htm#Accessory%20Decoder.

Thanks flashbang, that's an excellent link, and it confirms that

accessory decoders have positive common which means they won't work with traintronics signals out of the box. Latching relays looks like the answer for me. I will report back.

[ace10086]

using latching relays would also allow you to use the same decoder port for both a point motor and signal, if you so wished, which would reduce the number of decoders needed.

[idlemarvel]

I have successfully wired up a Traintronics 2 aspect colour signal to a Hornby
R8247 accessory controller, controlled using Railmaster via an Elite controller,
using a latched relay as suggested by rog and others.

This is a long posting

and will be very boring unless you have the same
requirement!

To recap the problem, DCC accessory controllers have a +12v positive common
(what is normally the black cable if you use Hornby points attached to the
middle of the three output

connectors on the accessory port) and the red and
green are ground 0v.

However the Traintronics signals require a ground common and +12v on the red and
green when they are set. So although you have a 12v difference between the
black and

the red, or the black and the green, whichever is set, it is the wrong
way round. Because the Traintronics use LEDs, the current direction is
important. You can't just reverse the wires because the signal wiring has the
same common wire for the

red and green lights, so they would be either both on
or neither on.

Here's how I did it. Bear in mind I am new to electronics so others with more
experience may have better ideas. It is written by a novice for the novice.

I used a Maplins

N38AW 2A Miniature DPDT Latching Relay at £4.09.
DPDT means double pole (on-on rather than on-off) double throw (two switches).
I didn't need two switches but I couldn't find a DPST. Latching means the
switch stays put and remembers the setting

until it is triggered again. Relay
means you feed a short pulse from one circuit to "flick the switch" (set or
reset in the jargon), where the switched circuit is electrically independent
from the circuit that flicks the switch. This is important

and the reason for
having the relay in this case, to enable us to deliver the correct voltage and
polarity to the signal.

For details of the N38AW, see this link:
http://www.maplin.co.uk/2a-miniature-dpdt-latchingrelay-37529

The full

specifications are here:
http://www.maplin.co.uk/media/pdfs/N38AW.pdf

(There are other suppliers and other devices, Maplins happens to be convenient
for me, and they do mail order if you can't get to a store.)

First, I connected the Traintronics

signal to the wiring block suppied with the
signal. See this diagram for details:
http://dl.dropbox.com/u/14067828/traintronics.jpg

Because the wires from the signal are very thin, and almost impossible to
connect securely to the screw connectors

IMO, I soldered short connecting leads
of thicker wire to these thin wires. See picture here:
http://dl.dropbox.com/u/14067828/IMG_0098.JPG

Then I configured the accessory controller to give the shortest pulse allowed
(0.1s). The specifications

for the relay say that it switches in 5ms so 100ms
is probably too long. To do this set CV 515 (for accessory port one) to value
1. See accessory decoder instructions or other posts if you are unsure how to
do this. Repeat with CV 516, 517 and

518 for the other three ports if required.

Now to wire the relay. I used green, black and red wires connected to the
accessory port + C and - like you would for Hornby point motors. Refer to the
N38AW specs diagram in the link earlier. Connect

black to pins 1 AND 2.
Connect red to 16 and green to 15. These connections set or reset the relay, so
at this stage you can try operating the accessory. You should hear a faint
click from the relay as you switch the accessory.

Now connect

the +12V for Green from the signal block to pin 6 and +12V for Red
to pin 8. This is the switched output from the relay. Finally connect your 12v
DC power (I used the Aux power outlet from the Elite which is actually +15v DC)
+ to pin 4 and the

- to the 0V on the signal block.

See the above picture to see all the connections. The orange and yellow wires
are the Aux power leads. Note that in my case I have "hard wired" the feather
lights to come on with the green - on my layout it will

always be on as the
"non-feather" route is a dummy for show which goes nowhere. See:
http://dl.dropbox.com/u/14067828/IMG_0099.JPG

Hope this helps somebody.

[stevecamden]

Now that I have got my points operating from Railmaster, I have been thinking of latching relays too (N38AW 2A Miniature DPDT Latching Relay) to control 2 aspect signals. I think I want to activate the relay in parallel with the point motor, but I don't

want to change the pulse time for the motor as this is working fine.

I was wondering what would happen if you gave the same pulse time to say the latch relay above to activate it. Is that a problem?

Any views on the cheapest way forwards greatly

appreciated!

I don't particularly want to use PAD ports solely for lights.

Steve

[idlemarvel]

I created this post a few years ago but recently I have changed my layout and needed to control the feather lights on my traintronics colour signals by the following points. Both points and signals are controlled by R8247 accessory controller via eLink

and Railmaster, and normally you can only set red or green. You need to read the preceding post to understand the general problem with traintronics and R8247.

I used another latched relay to switch the feather light as described in previous post, but

the difference is that the input voltage is provided by the green light from the signal, so that the feather only shows when green is showing, like in the prototype.

On the latched relay controlling the feather, the pins should be connected as follows:
Pins

1+2, 15 and 16 to C, + and - of the decoder port controlling the following point
Pin 4 from the signal green light input (pin 6 or 11 of the signal latched relay)
Pin 6 goes to signal feather

See youtube video http://youtu.be/D6w2gm_u6Lk to see

it in action.

[Michael_A]

idlemarvel said:

I created this post a few years ago but recently I have changed my layout and needed to control the feather lights on my traintronics colour signals by the following points. Both points and signals are controlled by R8247

accessory controller via eLink and Railmaster, and normally you can only set red or green. You need to read the preceding post to understand the general problem with traintronics and R8247.

I used another latched relay to switch the feather light as

described in previous post, but the difference is that the input voltage is provided by the green light from the signal, so that the feather only shows when green is showing, like in the prototype.

On the latched relay controlling the feather, the

pins should be connected as follows:
Pins 1+2, 15 and 16 to C, + and - of the decoder port controlling the following point
Pin 4 from the signal green light input (pin 6 or 11 of the signal latched relay)
Pin 6 goes to signal feather

See youtube

video http://youtu.be/D6w2gm_u6Lk to see it in action.