I had some 12VDC auto relays from my racing days laying around so I decided to put one to use
and let it operate the lights on a block signal.
The secondary side of the relay will work on AC without any problems.
The primary or coil side will not as DC is needed to operate the coil so the contacts will close.
I simply put a diode between the AC and the input side of the coil along with an electrolytic cap . The
negative side of the cap to ground. This worked fine using an insulated rail section for the coil ground. It
is trouble free while the 153C contactor has always been a headache.
Yup. The diode and capacitor will certainly do the trick.
Off subject, what did you used to race? Over the years, I've been involved with time speed distance rallyes, SCCA pro rallyes, a dirt track car, and radio controlled boats.
A bridge rectifier, like this one (276-268, 1.5 A, 400 V) from Radio Shack,
has the advantage of not drawing any DC current from your transformer. DC current tends to saturate the magnetic circuit and heat the transformer. This could be a problem unless you have a bigger transformer than you would otherwise need. (DC load current will also cause some modern "transformers" to shut down, in my experience) The full-wave DC from the bridge also needs half the filter capacitance of the half-wave circuit.
Do you know that you can operate a signal (like the 153) directly from the control rail with only an added lamp?
Bob Nelson
Yes, that's a good idea. I thought about using a bridge rectifier and had a home made one in my hand but it was bulky and ugly. The small one you show would have been perfect.
Does the lamp act as a current limiter when operating the signal or does it have another purpose?
8ntruck Yup. The diode and capacitor will certainly do the trick. Off subject, what did you used to race? Over the years, I've been involved with time speed distance rallyes, SCCA pro rallyes, a dirt track car, and radio controlled boats.
Here is a shot of my fastest car: A Chevy Beretta, 632" all aluminum motor, 0-153 mph in 4.7 secs. It was like being hit by a bus in the rear for 4 seconds.
That was one hobby that made this one look like a bargain.
The circuit is very simple: Red lamp to accessory voltage (or center rail). Green lamp to layout common (outside rails). Signal common to control rail. Wired this way, the red lamp is on and the green lamp is off when the train is on the control rail. Otherwise, both lamps are lit dimly in series. So the extra lamp is wired in parallel with the red lamp to drop its voltage almost to nothing, dimming it out and brightening the green.
The extra lamp should draw at least twice as much current at full voltage as the lamp in the signal. A parallel combination of two lamps of the same type used in the signal also works. This circuit was described at least 70 years ago by Albert Kalmbach (of Kalmbach Publishing fame), but using a resistor. A lamp works better, because, when the signal is red, it draws much less current than a suitable resistor does.
Very interesting, I have never heard of that one before. I will have to give it a try
Reminds me of the charging circuit of an old BMW motorcycle. The red gen warning lamp on the instrument cluster is an integral part of the circuit. If it burns out or isn't there, no more charge.
I should have mentioned that early 153 signals (before 1950) used number-50 7.5-volt screw-base lamps, with a 40-ohm resistor in series with the common terminal. To use these with the "Kalmbach" circuit, remove or jumper around the resistor and change the lamps to number-52 14.4-volt 100-milliampere screw-base lamps. After 1950, they used number-53 14.4-volt 120-milliampere bayonet-base lamps, without the resistor.
A good external lamp for use with either number-52 or -53 signal lamps is the number 57. It is a 14-volt 240-milliampere bayonet-base lamp. Or, as I mentioned, just use two of 52 or 53 in parallel.
Dave -
Nice car.
I'll agree, compared to fullsized motorsports, toy trains are quite the bargain.
I sure miss that car but not the racing expense.
1,000 a month just to race once a month plus one test and tune.
Not counting the cost of the car, engine, trans, rear, trailer and support equipment.
It is hard to describe the rush when going 0-100 in about 2 seconds.
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