dbduck I have just one question. Why did you use extra lamps as a voltage dropping means instead of resistors?
I have just one question. Why did you use extra lamps as a voltage dropping means instead of resistors?
I already have the lamps (about 5,000 of them, complete with sockets and linking wire) but would have had to buy resistors. Also, the 'extra' lamps were positioned to supply needed illumination to the hidden staging yard(s) adjacent to the panel.
Just realized - now I'm going to have to come up with a way to light the hidden switchwork! The lamp count over the yard just went down to 2!
Chuck (Modeling Central Japan in September, 1964)
I have mentioned before that I have been using a 12.6V center-tapped filament transformer for accessory power, and that I was planning to use some of my supply of 2.5V miniature Christmas lamps for panel indicator lights. I expected to have to put additional lamps in series to bring the voltage from the center tap to each end into line with the lamp capacities. I use the full 12.6VAC to power twin-coil switch machines - with a 3-amp capacity it has no need for a CD circuit boost and I use non-stick power contacts (AKA studs and probe.)
Well, I installed some lamps - and ran into a problem. Seems that they could take power all the way across the 12.6VAC winding, even with the 6.3VAC center tap not only dead but disconnected. Fortunately the circuit had a total of six lamps in series (four serving only as resistors) so nothing died...
After some consideration, I added a pair of opposed diodes between the transformer coil terminals and the lighting circuits. Viola, no more unintended cross-power. And - no more need for multi-bulb strings for voltage matching. Most of the circuits are designed for two indicators in series. Now, with the 1/2 wave DC showing only 3V between the center tap and either end terminal, two lamps will light adequately, but three produce only a feeble glow. Suddenly the need for thirty-odd lamps pretending to be resistors went away.
Actually, the reduction isn't all that big a deal. I have literally thousands of those miniature lamps, purchased for a couple of cents each (sockets included) during an after-Christmas clearance sale several years ago. What IS a good deal is that I no longer need to hide strings of 'resistor' lamps turning on and off for at odd times for no obvious-to-the-obsrever reason.
(That one filament transformer is only intended to power a single zone worth of indicators and switch machines. There will be others in other places, to be installed as construction proceeds.)