151 semaphore

If you're talking about the postwar 151 semaphore, you should be able to light the light all the time and then control the flat, it has three connections.  Wire power to the light directly, and control the coil with the track contactor.

Ground (common)

Lamp

Coil

Here's a diagram.

If you run them off track power and use modern engines, I would add a TVS on each  semaphore coil. These things can really generate voltage spikes. I would run them off a separate circuit using a dpdt relay. One contact set turning on track power on the block,the other running the semaphore off a separate accessory circuit. 

Switching track power with toggles and relays is described here

http://www.jcstudiosinc.com/Bl...=635&categoryId=

Dale H

The TVS is certainly cheap insurance, so that's a good idea.

You might want to take a look at the post war American Flyer semaphore.  It is bi stable and as you operate the semaphore it would turn your track on and off. 

I'm not so sure that the old 151 can take being energized for long periods of time.  I seem to recall mine getting quite hot.

You use low voltage on the light bulb circuit, works fine for long periods.  You can also substitute a lower power and/or higher voltage bulb.  The original bulb did get hot.

I think the simple answer is if you want the signal to show Red (Stop) when there is no track power to the block, the semaphore arm would be in the down (horizontal) position which requires the semaphore coil to be energized so obviously you can’t use voltage from that track block which would be zero.  If you want to show Green (Go) when the block has power the semaphore arm would be vertical with the light shining through the green lens which means the coil would not be energized. 

But you don’t want to use track voltage anyway because track voltage varies with the desired speed, the type of engine and the load on it (length and weight of consist) so it may not be high enough at all times to supply sufficient power to the coil to move the arm fully down to the horizontal position.

If you’re not using DPDT relays like Dale suggested, you would need a DPDT switch with one pole having track power on the normally closed contact and the other pole having power from another source (an accessory terminal) to the semaphore coil on the normally OPEN contact.  Power to the semaphore light would be constant accessory power.   

And I agree with others that the #151 is not designed to be activated for long periods of time.  Been there, done that and burned a few out!  You’re better off using block signals.

HTH,

Bill

The light bulb on all the time is fine. The coil on for long periods say 5 minutes will burn it up.

I would wire it so the bulb has its power source and common separate from the track. The coil can be powered from this source also. The coil common can be controlled via a relay with the N/O making common for the coil. The track hot would activate the relay.

I would use the postwar block signal and a relay. No burning coils.

One way possibly to reduce the current through the #151 semamphore is as follows:

1) Power the #151 semaphore from an "accessory transformer", independent from the train-powering transformer.

2)  Put a diode, a resistor, and the activating contactor in series with the power to the solenoid.

3)  From the resistor, by-pass the contactor and the solenoid coil with an electrolytic cacapacitor.

When the contactor is "open", power from the accessory transformer will charge up the electrolytic capacitor to full voltage.

When the contactor closes the circuit to the solenoid, the full charge on the capacitor will "kick" the solenoid into action, but the resistor will limit the amount of "holding" current which the solenoid will receive.

I would guess that the resistor would be somewhere in the range of 5 ohms to 10 ohms (5 watts), and the bigger the electrolytic capacitor, the better (maybe 1000 microfarads, 35 VDC).  Experimentation with different values may be necessary.

If I succeed in attaching the diagram, it may make this idea clearer.

In the diagram which I just posted a minute ago, I had forgotten to show a connection between the top output wire from the transformer to the light bulb in the #151 semaphore.

All this discussion about burning out the coil on the 151 is why I suggested looking at the postwar American Flyer semaphore.  They are a much better design for your application. 

The energized 151 makes noise when energized that would drive me crazy.  A simple solution for this application is an illuminated lockon (assuming conventional operation).

Has anyone attempted to operate the MTH 151 semaphore with DV as opposed to ac?  I just wired up a new one to ac and it makes so much noise that it's not pleasant at all.  I believe the noise is due to the ac supply to the coil magnet.  Also - I'm finding that it will not operate with the 14vac accessory supply.  Looks like it takes at least 16ac to operate the flag.  Wondering is anyone else has experienced that.

Thanks for posting the diagram of the 151.  Wish the manufacturer would do that.

Stephen

I found 2 AF's on Ebay.  One starting at $50 and one starting at $89.  4-5 of them would more than I am inclined to spend just to get some more "action" on my little RR.   I will keep watching.  I may consider just wiring the 151's in the stock Lionel manner with contactors.   I actually wanted to use them instead of lighted lock-ons, just for the action part.   thanks for all the info.

If you run with DC, note that it'll take less voltage due to the greater impedance running on AC.  With 16 volts DC, I suspect you could easily cook the coil.

If you run it on DC,lower the voltage until it just works.

Dale H

Thanks guys for your responses!  My timing probably wasn't the best in that I've had family from out of town visiting and they will be here through the end of June.  My young grandson, Patrick (just turned 7) is one of the visitors and we've been sidetracked with other 'train' projects.  Including the addition of a new-to-us Alaska (where he's from) diesel engine to Patrick Station.

I plan on following up with the two issues I've raised and will report back with what I find out as soon as I can.  -Stephen