I have an industrial grade regulated power supply made by Condor, rated at 15VDC at 5 amps. I am using it to power my Walthers 130' turntable, which is a little overkill I know, but I had it laying around. Now, I would llke to tap into some of the excess power to run about 30 Tortise machines. My question is how to reduce the voltage from 15 to around 8-9 to run the tortise machines; I find they run slower and quieter at less than 12 volts. Can I use a resistor on a separate line for the tortise's? If so, what rating should I use? OR, what other method can I use to cut the voltage? What voltage do you use on tortise machines?
Thanks,
Bob
Life is what happens while you are making other plans!
First, you need to know the resistance of the motor coil of your switch machines. Each motor will need its own dropping resistor. Essentially, you're cutting the voltage almost in half, so the resistor will be slightly lower value than the resistance of the motor.
To use a single resistor for the entire circuit, you'd actually need to build a simple voltage divider circuit. This is two resistors in series, connected across the output of your power supply. Motor failure could cause voltage shifts in this type circuit, so a simple regulator circuit would probably be better.
You could just try one of these from radio shack:
http://www.radioshack.com/product/index.jsp?productId=2062601#inTheBox
They're easy to wire and can be adjusted between 1.5 and 37 volts.
Just google the part number and you'll find wiring diagrams. You do not need the capacitors in the diagrams for this application. Just 2 resistors. There's even a link that tells you the value of the resistors to use.
Springfield PA
Put a couple of LEDs in series with the Tortoise motor - they will drop the voltage by about 2.1 volts each AND provide handy panel indicators.
You can also use resistors. A Tortoise draw about 18ma, a 270 ohm resistor would drop almost 5 volts, next value up is a 330 ohm, that owuld drop almost 6 volts. Use 1 resistor per Tortoise. Or a combination of series resistor and LEDs.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Randy,
I like your idea of using LED's because I had already planned to use them for turnout position indicators. I didn't realize they cut the voltage that much. The power supply is located next to my main control panel and would be easy to route the wires to the panel LED and then have another LED at the turnout for visual position when away from the control panel. I posted photos of the turnout position LED that I made look like a lantern several months ago, so this would work out just right. I guess I better start planning a circuit diagram to follow as I have about 25-30 Tortise machines.
PS: This is the turnout indicator LED I am using at the turnouts.
Just use a voltage regulator. 7808 or 7809 would do the trick. Last two digits is the output voltage. They are rated at 1 amp. Gang a couple of tortoise on each or use one per tortoise. At <35 cents a piece, they won't break the bank.
7809
7808
mfm37
How do you wire these voltage regulators ? they show 3 tabs and indicate a heatsink may be needed? I am not familiar with these but they look like a good idea.