I have a Digitrax DS64 controlling grade crossing signals on my layout. I have working LED crossing flashers and working movable gates. Everything works great except that the gates move up and down too fast. Therefore, I want to slow down the Tortoise by reducing the voltage driving it. How can I do this?
I am thinking this solution requires some type of voltage drop between the DS64 and the Tortoise, but not sure the best way to make that happen.
Jamie
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A pair of back to back diodes in series with either the wire to pin 1 or pin 8 of the Tortoise would work, but you'll need more than one pair - each pair will drop .7V. Or, even though you don't need it, put a 2-lead bi-color LED in series with the Tortoise. You can use it as an additional visual check that the gates are up or down, depending on which way you hool up the LED you cna make red be up or dow, the other will be green. or just hide it under the benchwork so you can;t see the light. The LED will drop about 2.1 volts
Or some combination thereof until it runs the speed you want. You don;t need any special high power diodes, the Tortoise only draws about 15ma max. Most diodes have a bandmarking the cathode end of the diode - by back to back pairs I mean take 2 diodes, and connect them together such that the banded end of one is connected to the plain end of the other, and the plain end of the first one conencts to the banded end of the second. Cut into the wire leading to pin 1 of the Tortoise and connect one end of the diode pair to the side coming from the DS64, connect the other end of the diode pair to the side going to pin 1 so the diode pair replaces the cut section of wire. One pair will probably not be enough, so connect addional pairs in line with the first one and so on. Like I said, I'd start witht he LED, that might be enough drop. Two LEDs would be about 4.2 volts.
Resistors are not recommended because the current through the Tortoise is not constant. It draws more when it stalls, so the voltage to the motor will be lower when it stalls than when it's running, sort of the opposite of what you want.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
You should be able to use a resistor in series with one of the tortoise motor leads. Since you are a model railroader, I think you should have a few resistors in your parts boxes. Start with the low values below 100 ohms. Unless you have a decade resistance box, selecting the correct size will be trial and error. (If you put two resistors in parallel, the resistance of each one will be reduced.)
Once you have found a size that works, measure it with an ohm meter and then buy the same value or very close to it. The wattage ratting can be 1 watt to be safe.
If you don't have an ohm meter (digital multimeter) you should have one for troubleshooting. After all, model railroads run on electricity and you need to test them somehow sometimes.
Elmer.
The above is my opinion, from an active and experienced Model Railroader in N scale and HO since 1961.
(Modeling Freelance, Eastern US, HO scale, in 1962, with NCE DCC for locomotive control and a stand alone LocoNet for block detection and signals.) http://waynes-trains.com/ at home, and N scale at the Club.
To expand on Randy's excellent analysis, two series connected Zeners would work too (reverse one of them). I also would not recommend resistors. Likely though the bipolar LED will get the speed to a reasonable value.
Karl
The mind is like a parachute. It works better when it's open. www.stremy.net
Thanks for the great info. If I use a two-color LED, can I just place it inline without the use of a resistor and not worry about burning out the LED? Also, can I use multiple LEDs in series to bump the voltage drop? I used to know all this stuff in another time. Jamie
Yup. The Tortoise draws a max of 15ma and since the LED will be in series, it will also see no more than 15ma, which is well within the limits of most any LED. That wil drop about 2.1 volts, check the LED forward voltage rating - that's how much it will reduce the voltage to the Torotise by. More than one in series will drop more - so if it's 2.1 volts per LED, two in series will drop 4.2 volts. The 2 lead bicolor ones are easiest to work with since they are two LEDs back to back in one package with just 2 wires - you need an LED or dioide in each direction since the Tortoise works by reversing the polarity tot he motor - just a regular LED, or a regular diode, will allow the Tortoise to go one way but not the other. 2 lead bicolor LEDs take care of that for you.
rrinker Yup. The Tortoise draws a max of 15ma and since the LED will be in series, it will also see no more than 15ma, which is well within the limits of most any LED. That wil drop about 2.1 volts, check the LED forward voltage rating - that's how much it will reduce the voltage to the Torotise by. More than one in series will drop more - so if it's 2.1 volts per LED, two in series will drop 4.2 volts. The 2 lead bicolor ones are easiest to work with since they are two LEDs back to back in one package with just 2 wires - you need an LED or dioide in each direction since the Tortoise works by reversing the polarity tot he motor - just a regular LED, or a regular diode, will allow the Tortoise to go one way but not the other. 2 lead bicolor LEDs take care of that for you. --Randy
does the voltage feeding the DS64 affect the output voltage? if you fed it with 9 volts from PSU and just used the loconet to issue commands would the 64 outputs have a lower voltage anyway???
locoworks does the voltage feeding the DS64 affect the output voltage? if you fed it with 9 volts from PSU and just used the loconet to issue commands would the 64 outputs have a lower voltage anyway???
According to the Digitrax DS64 documentation, when an external power supply is used, the static output voltage for slow motion turnout motors will be 14 volts (I incorrectly stated 15 volts in my previous post). Jamie
ok, but IF you only give it 9 volts to start with how would it put out 14? i could understand it having a limiter for voltage so if you fed it with 20 it only gave 14 to the motor, but not a step up tranny to increase it from 9 - 14. if ithe 64 would work on 9 volts i'd expect it to slow things down on the out side too as i doubt it would be using the CDU for slow mo stuff??
Frome the Digitrax Manual: 2. Connect a 12-14vdc, 300ma power supply to the AX1(-) and AX2(+) terminals on the front of the DS64.
Frome the Digitrax Manual:
2. Connect a 12-14vdc, 300ma power supply to the AX1(-) and AX2(+) terminals on the front of the DS64.
Dave
Lackawanna Route of the Phoebe Snow
9V means the DS64 wouldn;t work, or at least be flakey. It needs at least 12V. Plus if it's also connected to track power, it can pull from there. In a non-Digitrax system is MUST be connected to the track to get DCC commands, with a Digitrax system it does not need to be connected to the track and it will get commands over the Loconet, with power coming from the Aux power terminals (preferred method as a short ont he track won't cut power to operate turnouts - with the track shorted commands would still come over the Loconet).
Phoebe Vet Frome the Digitrax Manual: 2. Connect a 12-14vdc, 300ma power supply to the AX1(-) and AX2(+) terminals on the front of the DS64.
thanks for the bigger text, it made more sense that way. i was only throwing an thought out there.