I'm in the process of installing Tomar makers on a caboose. They work fine on a 1.5v battery, but I can't get them to work off the track power. I have the bulbs wired in parallel. I've tried a 1K, 680 and 470 resistor, but the lights won't light.
I have track voltage before the resistor, but almost no voltage after.
Any bright ideas?
Nick
Take a Ride on the Reading with the: Reading Company Technical & Historical Society http://www.readingrailroad.org/
Nice pun.
What I'd suggest is a small circuit consisting of a bridge rectifier powering a LM317 (T or LZ, depending on available space) voltage regulator. I don't have a diagram handy at the moment, but I'll try and knock one together when I get home.
Here's something similar used for 1.5v bulbs with DCC decoders:
http://www.tonystrains.com/technews/install-lamps-decoders.htm
Scroll down to section 3, on the IC regulator circuit. As is, that one will put out 1.25 volts, which will be slightly dimmer than normal. You'd connect the Vin lead (or "blue wire" on the diagram) to the + output from the bridge rectifier, and the "Function Output" to the - side of the rectifier.
I've used a similar circuit to power lights in a passenger car before. IT'll work on both DC and DCC, but it prefers DCC.
Robert Beaty
The Laughing Hippie
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The CF-7...a waste of a perfectly good F-unit!
Then it comes to be that the soothing light at the
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your way. -Metallica, No Leaf Clover
Are you running DC, or DCC?
Are the Tomar bulbs incandescent or LEDs?
My first thought is that if they're LEDs, and you're running DC, then the polarity is wrong. LEDs should light on DC.
Do you have a meter? If so, set it for 100 milliamps or so, and see how much current flows through the lights with the battery in place. (Put the meter in series with the lights to measure current.) This will tell you the resistance of the lights. Then, measure the track voltage you're seeing, so we can figure out the right size resistor.
It takes an iron man to play with a toy iron horse.
The user in the below photo uses and sells the kit. I have the kit also.
http://www.members.optusnet.com.au/nswmn/flicker_free_JB.htm
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Looking at that circuit I see a few issues. FOr DCC, instead of a bridge rectifire you should probably use 4 individual 1N5401 diodes, they react faster than basic rectifier diodes. Secont, R2 will almost certainly need to be less than 1K, since you will have no more than 5.1 volts across the zener diode.
For DCC - th idea of using an LM317 variable regular is probably the best. If the lamps are 1.5 volt, the lowest voltage usually possible from the LM317 is about 1.2 volts and this is how it should be wired. The 1.5 volt bulbs will last much longer on 1.2 volts and still be plenty bright. if they are LEDs - wire the LM316 as a current source. Various circuits for this can be found on Rob Paisley's site http://home.cogeco.ca/~rpaisley4/CircuitIndex.html
If the markers are in a powered loco, connect them to a function. Even if they are on a caboose, you might want to consider a function only decoder so you can turn them on and off. The old trick in a DC loco was a pair of diodes in series with the motor (two pair actually, one for each direction) with the lights across them - this gives the lights a constant 1.2-1..4 volts. For this to work in an unpowered car or with DCC you need a load of some sort, so this isn't very practical. Even if they are on a caboose, you might want to consider a function only decoder so you can turn them on and off.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
My layout is DCC, and the markers use bulbs not LEDs.
Thanks for the tips. Eventually, as the budget allows, all the cabooses will have function decoders.
Why not use an old light board from a locomotive. They put out 1 1/2 volts to the headlights. If you have installed any decoders, then you should have an old light board around. If not, they should be easy to come by.
By the way, how are you picking up track power in your caboose?