Wiring two signals together

[Heinz57]

Hi all,

 

I am in need of some assistance with some signal wiring. Basicaly, on each track into the shed on my layout I will have two opposing signals, one for entry and one for exit. Plus a flashing beacon inside the shed that is on should anything be moving. I am looking to operate the two opposite signals and warning beacon from the same switch, but I'm not sure on the best way to do it. My rather crude diagram below describes it best...

 

 

So what is the best way to acheive this? I did originaly think of a standard on-off-on toggle switch, but I figured this would keep the red aspect on all the time even when the signal is green.

 

Any advice you can give is very much appreciated.

 

Matt

[Brian]

How about a 3 position Guittar switch? - Offers On/On/On switching.  Or a three position rotary switch with a few steering diodes perhaps?

[phixer64]

Hiya Ive done this on my layout. 2 signals controlled by one Wired up the first signal as normal.
Left signal - switch down = red. Switch up green

Right signal - switch down - green . Switch up red. All wired to a single pole double throw switch. 

 

Hope this is a help. 

Regards Jeff

[DCB]

I can't think of a three position slider or lever switch which can do those three different items.  Most are on off on some are off on on but a double pole on on on is a new one on me.  A standard three way four pole rotary would do it but the action is rotary.   I think I would make a unit out of a couple of microswitches and a diode matrix.

[Michael Hodgson]

13 hours ago, phixer64 said:

Hiya Ive done this on my layout. 2 signals controlled by one Wired up the first signal as normal.
Left signal - switch down = red. Switch up green

Right signal - switch down - green . Switch up red. All wired to a single pole double throw switch. 

 

Hope this is a help. 

Regards Jeff

If I understand you correctly that means one signal or the other must always be green, even when you are running a train from the background towards us.

[meil]

RS do quite a number of three way Toggle switches that look to be what you want. An example is their 734-7050.

You would control operation by suitable use of diodes.

Edited June 10, 2022 by meil

[DCB]

Red Green + Beacon to Green Red + Beacon is dead easy, its the Red Red with no Beacon which is the awkward one.  It needs a 6 terminal 3 way switch which connects left bottom to right bottom in position 1   left top to right top in position 3 and left middle to right middle in position 2.  Then you can feed a diode matrix and Robert's your Mother's Brother.  They usually connect left bottom to left middle, and also right bottom to right middle in position 1 and   left top to left middle, and also right top to right middle in position 3 and connect nothing in position 3.

[Heinz57]

Thanks chaps,

 

I have found these on RS, would they do the job?

 

https://uk.rs-online.com/web/p/toggle-switches/7347053

 

https://uk.rs-online.com/web/p/toggle-switches/7347012

 

Wiring in diodes isn't a problem, but what size do I need and where would I need to wire them?

 

Cheers,

 

Matt

[DCB]

2 hours ago, Heinz57 said:

Thanks chaps,

 

I have found these on RS, would they do the job?

 

https://uk.rs-online.com/web/p/toggle-switches/7347053

 

https://uk.rs-online.com/web/p/toggle-switches/7347012

 

Wiring in diodes isn't a problem, but what size do I need and where would I need to wire them?

 

Cheers,

 

Matt

I don't believe so.  You need an SPTT ( Single pole triple throw.)  On On On.  which is very much a specialised  odd ball,

Centre off ( on off on) are common, Centre on (off on  off)  less so and I never did fins the off on on sliders I needed to wire my isolated sections so had to use on off on annoyingly.

 

Sort of thing old fashioned electronics shops would have lying around  but you have to take your own multimeter to identify them. I am racking my brain cell for if Lucas made any for cars circa 1965 with the old Minis /1100s etc.  I had quite a few spare ones years ago.   

Edited June 10, 2022 by DCB

[melmerby]

You lot don't look very hard.

This took all of 30 second to find:

https://cpc.farnell.com/alps/stsss9131/slide-switch-sp-3-pos-vert/dp/SW04231?st=3 position switches

 

It says single pole 3 throw

Edited June 10, 2022 by melmerby

[DCB]

10 minutes ago, melmerby said:

You lot don't look very hard.

This took all of 30 second to find:

https://cpc.farnell.com/alps/stsss9131/slide-switch-sp-3-pos-vert/dp/SW04231?st=3 position switches

 

It says single pole 3 throw

 

That should do it.   Well done.

[Heinz57]

2 hours ago, melmerby said:

You lot don't look very hard.

This took all of 30 second to find:

https://cpc.farnell.com/alps/stsss9131/slide-switch-sp-3-pos-vert/dp/SW04231?st=3 position switches

 

It says single pole 3 throw

 

Cheers.

 

Unfortunatly they don't have enough in stock for what I need (I need seven). But I'm guessing these would be a suitable alternative? They are SP3T ON-ON-ON

 

https://uk.farnell.com/te-connectivity-alcoswitch/3-1825139-9/toggle-switch-sp3t-5a-120v/dp/3406892

 

Would I still need any diodes or anything or would the switch on its own do the job?

[melmerby]

3 hours ago, Heinz57 said:

 

Cheers.

 

Unfortunatly they don't have enough in stock for what I need (I need seven). But I'm guessing these would be a suitable alternative? They are SP3T ON-ON-ON

 

https://uk.farnell.com/te-connectivity-alcoswitch/3-1825139-9/toggle-switch-sp3t-5a-120v/dp/3406892

 

Would I still need any diodes or anything or would the switch on its own do the job?

They look the same functionally and somewhat more elegant. You are paying for a better switch.

They are AFAIK just three pairs of contacts, each pair makes depending on the switch position.

e.g.

 

[Dave John]

With a 3 position switch you would still need some diodes. Rough sketch. 

 

 

 

Any diodes will do , but 100 for under 4 quid... 

 

https://www.ebay.co.uk/itm/152055974146?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D2%26asc%3D239816%26meid%3D3d3b721c4234421a87ec35fdd8044d60%26pid%3D101224%26rk%3D2%26rkt%3D5%26sd%3D125160858155%26itm%3D152055974146%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganicWeb%26brand%3DUnbranded&_trksid=p2047675.c101224.m-1

Edited June 10, 2022 by Dave John

[John ks]

Here is a slightly unconventional way to wire the signal that requires a SPSP centre off switch (on-off-on)

And using LEDs for the signal aspects

 

 

Hopefully the drawing explains it all

The diodes are 1N4004 or similar (1N4004 is a 1A 400V diode, a 1N4001 is a 1A 100v diode & would also be OK)

John

[Heinz57]

Thanks for the drawings.

 

I have some SPSP on-off-on switches in stock already, making it cheaper!

 

The only thing I can't quite get my head around is if the red aspects are connected to the centre pin on the switch, the same as the live wire. How will it turn the red off when the green is on?

 

Matt

[DCB]

Looks like the diode from the feed to the green shorts it out,    I'm not sure about the wisdom of shorting the LED with a diode, you have a diode and a resistor and nothing else across + ve and -ve.   I don't like resistors at the best of times, but it's an interesting idea.

[John ks]

The new drawing only shows the red LED which may be a bit easier to see what is happening

In the LH drawing with the switch off  current flows from the positive through the LED then the resistor to negative & the LED lights

In the centre drawing with the switch on  the diode (as DCB explains) shorts out the LED 

Another way to look at it, the voltage at point B will be 12 volts

The voltage at point A will be 12 volts minus the forward voltage of the diode (1 Volt) ie 11 Volts

The Voltage across the LED will be 1 Volt which shouldn't be enough to turn on the LED as most LEDs need a forward Voltage greater than 1.8V

 

 

If you want to prove that it works then build the test circuit

With the diode disconnected the LED lights

With the diode connected the LED  is off

While i was writing this i built the circuit on a breadboard & it works

John

 

 

 

[Heinz57]

1 hour ago, John ks said:

The new drawing only shows the red LED which may be a bit easier to see what is happening

In the LH drawing with the switch off  current flows from the positive through the LED then the resistor to negative & the LED lights

In the centre drawing with the switch on  the diode (as DCB explains) shorts out the LED 

Another way to look at it, the voltage at point B will be 12 volts

The voltage at point A will be 12 volts minus the forward voltage of the diode (1 Volt) ie 11 Volts

The Voltage across the LED will be 1 Volt which shouldn't be enough to turn on the LED as most LEDs need a forward Voltage greater than 1.8V

 

 

If you want to prove that it works then build the test circuit

With the diode disconnected the LED lights

With the diode connected the LED  is off

While i was writing this i built the circuit on a breadboard & it works

John

 

 

 

 

Thanks for explaining, that makes more sense to me now.

 

The signals I am using are rated at 12v (to be specific I am using the shunt signals from Absolute Aspects). Obviously these are usualy connected to the 12v supply without the need for an extra resistor but to make the above circuit work will I still need the extra resitors?

 

Cheers,

 

Matt

[SHMD]

How many wires do the signals have?

(If the signal only has three wires - for two LEDs (usually, but not always, Common Cathode) - then this will also limit which circuit you can use.)

 

 

Kev.

 

[Heinz57]

Three wires - red signal, white (green) signal, common ground

 

Cheers,

 

Matt

[AndyID]

3 minutes ago, Heinz57 said:

Three wires - red signal, white (green) signal, common ground

 

Cheers,

 

Matt

And you apply plus 12 volts to turn on a signal. Correct?

[DCB]

As I read it with resistors built in to the signal and only three wires you can't connect a wire between the led and its built in resistor.  Simply deleting the resistor will end up with a  dead short through the diode from the green lamp, you will get two reds in the middle position and nothing, except the overload trip clicking for left or right.

Its like walking across the River Thames.  it worked in 1666 when the river froze, but change one tiny detail,, the temperature, and it stops working.

[Heinz57]

Yes you apply a 12v DC feed to turn on the signals. I belive the LEDs inside are rated at 12v, I don't think there's any resistors inside the signal head.

[AndyID]

3 minutes ago, Heinz57 said:

I belive the LEDs inside are rated at 12v, I don't think there's any resistors inside the signal head.

 

That's quite possible. You can get LEDs with built-in current limiters that will run on 12 volts.