Dapol 4mm Semaphores

Post

Posted
Rating:
#139631 (In Topic #7503)
Avatar
Full Member

Wiring

My friend dropped by yesterday all excited because he just received a pair of subject signals.  They do look good although probably won't suit those who are looking for accuracy to the nth degree.  The instructions state that only 16VAC must be used (def. NOT DC) which is fine.  Trouble is, the old DC controller I was going to use has a 19VAC accessory output.  Another friend advises that the LED spectacle will probably be brighter than it should be on 19VAC and that the arm will most likely move quicker than it should.  To my mind the voltage might be better at something less than 16VAC since oil lamps weren't that bright and signal arms moved at a leisurely pace.

Has anyone gotten around to fitting these yet and if so, what did you use for power?

John

 

John
 
Online now: No Back to the top

Post

Posted
Rating:
#139632
Avatar
Inactive Member
Hi John.

As the LEDs are DC, would it be possible to fit a ballast resistor to them?

Cheers
Online now: No Back to the top

Post

Posted
Rating:
#139633
Avatar
Full Member
I'm like the proverbial sack of hammers when it comes to 'lectrics.  I will meet with our club's electrical whiz on Sunday to discuss this further.  I will report on progress if no-one has done them yet.

John

 
Max, I looked up "ballast resistor" and I now think I understand where you are coming from.  For LEDs in parallel (as these will be) a BR in series with each LED will equalise (to some extent) the current so that each lamp should be of more or less equal brightness.

Last edit: by Brossard


John
 
Online now: No Back to the top

Post

Posted
Rating:
#139705
Avatar
Full Member
Hi John,

You can very easily reduce 19v to 16v provided you know the current draw in amps. If the signals are rated at 5mA, by introducing a 600 ohm, 1 watt resistor into BOTH the Positive and Negative inputs to the signal you will reduce the 19 volts to 16 volts. If they are rated at 10mA then use 300 ohm resistors This is calculated using Ohm's Law and if you want the details I will provide them.

I haven't examined one of the Dapol signals myself but LEDs generally operate at around 2.2 volts so there are probably built-in resistors to take the 16 volts down to 2.2 volts.

Regards,
Trevor
Online now: No Back to the top

Post

Posted
Rating:
#139706
Avatar
Full Member
Be good to see some pictures as I am thinking of buying some of these.

Bob
Online now: No Back to the top

Post

Posted
Rating:
#139718
Avatar
Full Member
Thanks for the info Trevor.  I have some regular resistors so I can do some testing.

Cheers

 

John
 
Online now: No Back to the top

Post

Posted
Rating:
#139732
Full Member
I advise caution before trying to use resistors to drop the AC voltage. These models use solenoids to drive the semaphore arms and will therefore NOT draw a "simple" current from the AC supply.

I would recommend using a 16v AC supply such as those provided by Hornby and Bachmann for their controllers. They can usually be found very cheaply for both 110v and 220v mains supplies.
Online now: No Back to the top

Post

Posted
Rating:
#139733
Avatar
Full Member
Now I'm confused.  I may end up getting a specific power supply but really wanted to put the old DC controller to use.  I should have mentioned that the layout is DCC.  An alternative might be to use a DCC device to activate the signal (solenoid point motor accessory decoder perhaps?).  Taking power direct from the DCC bus (11VAC or thereabouts) should illuminate the lights (in the same way as the Pullman cars I was running today).

Thanks for the responses.

Cheers

John


Edit: Thinking about it, an accessory probably won't do since it outputs a DC voltage (pulse in the case of solenoid or steady state in the case of slow mo') 
 

 

Last edit: by Brossard


John
 
Online now: No Back to the top

Post

Posted
Rating:
#139740
Avatar
Full Member
To be safe I would set up a test rig to try different resistor combinations on the 19v output and test to see what voltage you are getting.

Regards,
Trevor
Online now: No Back to the top

Post

Posted
Rating:
#139741
Avatar
Inactive Member
Having just lived through a major catastrophe (not of my making, I hasten to add), I would never use DCC bus power to drive anything else.
Online now: No Back to the top

Post

Posted
Rating:
#139742
Avatar
Full Member
Thanks chaps.  Tooth sucking in progress.

John

Edit:  I just did some testing using an old light bulb.  When connected to 19VAC it looked like it was going to burst into flames.  I then connected 500 K resistors onto each line - this time the bulb didn't glow at all.  Finally I connected 5ohm resistors to each line - this time the bulb glowed, but not brightly.  However, there was quite a bit of smoke from the resistors.  I haven't a lot of variation in resistor values.

So far instructions read - and heeded - nothing broken…yet.

I will probably go shopping for a proper power supply tomorrow.

 

 

Last edit: by Brossard


John
 
Online now: No Back to the top

Post

Posted
Rating:
#139750
Full Member
[user=565]Brossard[/user] wrote:
Now I'm confused.  I may end up getting a specific power supply but really wanted to put the old DC controller to use.  I should have mentioned that the layout is DCC.  An alternative might be to use a DCC device to activate the signal (solenoid point motor accessory decoder perhaps?).  Taking power direct from the DCC bus (11VAC or thereabouts) should illuminate the lights (in the same way as the Pullman cars I was running today).

Thanks for the responses.

Cheers

John


Edit: Thinking about it, an accessory probably won't do since it outputs a DC voltage (pulse in the case of solenoid or steady state in the case of slow mo') 
 

 


Control from a DCC accessory decoder should use a small relay.

The signals have a permanent connection to 16v AC and a separate pair of wires which when joined momentarily cause the signal to change state. If these wires were connected to a relay operated by a pulsed decoder output, then each time the decoder was operated the signal would change.

The LED is white and permanently lit from the 16v AC supply - clearly with a built in diode and resistor in series. It shines through the spectacle plate of the arm to show red or green.

Last edit: by Geoff R

Online now: No Back to the top

Post

Posted
Rating:
#139758
Avatar
Full Member
Thanks Geoff.  There's a consensus that a decoder and relay is the way to go for DCC.  However, my friend is impatient so I will get him a dedicated AC power supply today.

It's a puzzle to me why Dapol designed this for AC and didn't make any provision for DCC.  DC would be so much more convenient and voltage could be varied.  

Wondering what the standard for AC accessory output is for UK controllers.  Over here it seems to be 19VAC.

John

 

John
 
Online now: No Back to the top

Post

Posted
Rating:
#139762
Full Member
The standard Hornby and Bachmann controllers run off 16v AC. They use a mains plug type power supply which has a cord for the 16v AC. This connects to the input of the controller - same is used, at least by Bachmann, for the input to their basic DCC controllers.

Clearly the output of the standard controller is variable up to 12v DC (although these are not "smoothed" DC, but just rather crudely controlled half AC waveforms. Been produced for years and are perfectly adequate for controlling train sets.

So 16v AC has been the accessory standard. Used to drive older lamp style signals and platform lighting, etc, and more up to date also used to drive LED lighting which have in built diodes and resistors like the Dapol Signal.

If you have a look at RMweb - which several folk on here also belong to - you will find a whole section on Dapol, including the semaphore signals. There is also a member called DapolDave who appears to be one of the main designers of these signals within Dapol and is very responsive to questions and suggestions.
Online now: No Back to the top

Post

Posted
Rating:
#139763
Avatar
Full Member
Right Geoff.  Thanks for the info, it certainly explains Dapol's design choice here.  I asked this question on RMweb thread but I think it got buried in some recent argy barging.  I could drop a PM to Dapol Dave - but he's unlikely to deviate from the official advice.  I'm getting some advice from MR Forum as well.

We are on a long weekend here but all the shops are open…all that is, except the one I need for the power supply :sad:

John

John
 
Online now: No Back to the top

Post

Posted
Rating:
#139831
Avatar
Full Member
A bit of an update on this conundrum.

I got myself a 12VAC, 1A power supply today (actually measures 13.5VAC on my meter). The store I went to only had the fixed kind. The next voltage up was 18VAC (sheesh!) It was only $8 so the risk is low.

After a few false starts (including blowing the power supply fuse - easily fixed) I got the switch wiring done. When I connected to semaphore motor to the switch and pressed it, nothing happened. I checked the switch circuit and it functions with 1) an old light bulb and 2) the signal diode itself.

Since I had caused a short earlier I was afraid that I might have fried the semaphore motor so connected the second signal to the switch - same thing, nothing happened.

Feeling just a bit exasperated now. Surely the power supply I have should make the arm move even if slower than normal.

Thoughts anyone?

People in North America - take note. If any of you have any bright ideas, I'd like to hear them.

John

John
 
Online now: No Back to the top

Post

Posted
Rating:
#139851
Sol
Avatar
Site staff
Sol is in the usergroup ‘Super-moderators’
Use the multimeter in ohms mode to confirm the solenoid coil is still OK - even reverse the leads to make double sure there is not a diode in the circuit internally.

Ron
NCE DCC ; 00 scale UK outline.
Online now: No Back to the top

Post

Posted
Rating:
#139853
Avatar
Full Member
Hi Ron, checked the leads on both signals.  Both show open in both directions.  There is a capacitor in the circuit according the instructions.

I have contacted Dapol Dave (Product Development Mgr I think) hoping he can shed some light.

I'm wondering if the circuit needs a pulse of at least 16VAC to trigger the arm movement.

I will advise.

Cheers

John

John
 
Online now: No Back to the top

Post

Posted
Rating:
#139896
Full Member
John, I have not see one of these in the flesh, but I thought it had four connections - is that correct?

In which case I expected there to be a permanent connection between the two which supply power and the AC supply. Then the LED should be permanently lit.

The other two wires go to the switch and when it is momentarily operated, one of the coils is energised throwing the signal to its opposite state. This action also reverses the internal connections to the coils so that the next time the switch is operated, the other coil is energised returning the signal to the initial state.

You would almost certainly NOT see a continous circuit with a multimeter for two reasons. One is that the capacitor may well be in series to ensure a good strong pulse of current - a bit like a CDU, and secondly that there is only a circuit through the coils while the switch is being operated.

 
Online now: No Back to the top

Post

Posted
Rating:
#139898
Avatar
Full Member
Sounds like you have it Geoff.

There are indeed 4 wires. 

Red and Black directly connected to the power supply and LED pemanently ON.

2 Yellow wires for the arm actuator, conected to a spring loaded press to make switch.  A passing contact switch would be better - no chance of the switch being held on either inadvertently or due to switch failure.

I am standing by for advice from Dapol Dave.

Since the first batch of these signals sold out quickly, there MUST be some people who have successfully wired these up and got them working. 

Since I am in N America, I feel hamstrung by being unable to find a power supply that meets the 16VAC spec.  If I am having trouble, the not insignificant number of UK modellers over here will have trouble too - something that needs nipping in the bud.

John

 

John
 
Online now: No Back to the top
1 guest and 0 members have just viewed this.