Theoretically, a 12V transformer with a bridge plus a filter cap ought to be a bit OVER 12V when all is said an done, the cap allows the voltage to operate at peak rather than RMS. Compensated a bit for the diode drops in the bridge.
Yes, Toritose stall current is under 15ma, that means it takes over 66 of them to equal a full amp. So yeah, doesn;t really matter how they are pwoered in the long run, unles you have a great big layout with hundreds of them. What's really nice is hooking a pair of LEDs in series with the motor for indicators, no resistors needed, the 15ma of the Tortoise being well within safe operating levels for most LEDs. Plus it serves to drop the voltage a bit, with a 12V supply and 2 LEDs in series, you're at 8V or less to the Tortoise. Even 1 LED, or a red/green pair anti-paralleled (same as a single bi-color LED), you cut 12V down to under 10V. Quieter and slightly slower in operation, PLUS position indicators with no extra wiring.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
DigitalGriffinThe tortoise warranty is void if you pump over 12VDC into it.
True of course - always measure the voltage to ensure you're not applying too much, and use appropriate sources of resistance.
Most people use 9 volts.
Most of the layouts in my immediate work group, plus those where I operate regularly, use 12V power supplies, which ends up somewhat less once run through the rectifier, filter cap, etc. Might be a regional thing like which DCC system is more popular.
Rob Spangler
The tortoise warranty is void if you pump over 12VDC into it. Read the fine print.
To be honest you can do it. I used to. But as soon as you short the layout (ie: Entering the frog the wrong way) you lose the ability to switch the points. So I used a dedicated 12V supply now.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
narrow gauge nuclearMost here know this, but all tortoise machines draw full stall current forever! Sure it is only a few tens of milliamps, but continuous and unending, nonetheless. This is part of the beauty of the tortoise that allows it to be electronically controlled via DCC without relays or toggle switches.
Which is why I find the worrying about powering a Tortoise from the DCC bus, be it temporarily or otherwise, to be a bit silly. Conceptually there is no difference between powering the Tortoise through an accessory decoder or through other means (e.g. a rectifier, filter capacitor and toggle switch). With the decoder, there's additional circuitry between the DCC bus and the Tortoise, but all it really does is act in place of the toggle to switch the rectified and filtered DC polarity to the machine, using electronic commands instead of something manual.
narrow gauge nuclearThis is part of the beauty of the tortoise that allows it to be electronically controlled via DCC without relays or toggle switches. The only way to avoid the continuous drain is a three postiion, center-off, DPDT switch..... on-off-on
I don't understand what you are getting at here. One cannot control a tortoise directly from DCC. One needs a stationary decoder, which is (usually) designed to provide continuous current. So you still need something between DCC and tortoise.
And the tiny current drain makes zero difference. Why would anyone bother with a center-off DPDT in a permanent installation that could result in a tortoise being stopped partially thrown, causing derailments? For the temporary testing the OP is talking about, he's obviously not going to leave a 9-volt battery connected for days.
These vague statements aren't correct and could mislead someone new to using tortoise machines.
Layout Design GalleryLayout Design Special Interest Group
narrow gauge nuclear The only way to avoid the continuous drain is a three postiion, center-off, DPDT switch..... on-off-on Richard
Richard
...Or use a Digitrax DS64, which gives you the option of cutting the output power to the Tortoise after a 16 second delay. Just set OPSW 9 to Closed.
Most here know this, but all tortoise machines draw full stall current forever! Sure it is only a few tens of milliamps, but continuous and unending, nonetheless. This is part of the beauty of the tortoise that allows it to be electronically controlled via DCC without relays or toggle switches. The only way to avoid the continuous drain is a three postiion, center-off, DPDT switch..... on-off-on
If I can't fix it, I can fix it so it can't be fixed
richhotrain True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us.
True wisdom comes to each of us when we realize how little we understand about life, ourselves, and the world around us.
Often, Grasshopper, it is not the answer we seek, but merely the right question.
It takes an iron man to play with a toy iron horse.
MisterBeasley Socrates would have loved what goes on here.
Socrates would have loved what goes on here.
LOL
Alton Junction
MisterBeasley richhotrain What do you say? Yes or No? Apply the Socratic method, as I frequently do. (However, instead of hemlock, I usually substitute an India Pale Ale.) The OP, as we have seen, was seeking a method for testing a Tortoise. Although the original question posed was slightly different, this was his intent, so by inquiry and intelligent discourse, we have led him to a better solution. Socrates would have loved what goes on here.
richhotrain What do you say? Yes or No?
What do you say?
Yes or No?
Apply the Socratic method, as I frequently do. (However, instead of hemlock, I usually substitute an India Pale Ale.)
The OP, as we have seen, was seeking a method for testing a Tortoise. Although the original question posed was slightly different, this was his intent, so by inquiry and intelligent discourse, we have led him to a better solution.
Ok .... I've apparently somehow misread the whole thing. I was under the impression the OP was asking if he could use the DCC on his rails, fed through a bridge rectifier and then through a dpdt switch as a means of testing his tortoise switch machines.
Don't know how I interpreted it as that, when in fact he was apparently just seeking any method for testing Tortoise switch machines.
No wonder I was never any good in English ....
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Mark R. Why does a simple yes / no question always seem to evolve into what "should" be done or what everyone else does. The OP WANTS to use the DCC track power because it's right there beside what he's working on .... he just wants to know if it will work for testing .... yes or no. Mark.
Why does a simple yes / no question always seem to evolve into what "should" be done or what everyone else does.
The OP WANTS to use the DCC track power because it's right there beside what he's working on .... he just wants to know if it will work for testing .... yes or no.
I have a crossover on an isolated branchline where I needed to use switch machines, but didn't want to have a separate power supply just for two machines, or run a long connection from the rest of the switch machine supply elsewhere on the layout. I tapped into the DCC bus for the branch, which is on its own circuit breaker, and powered the Tortoise machines after running through a diode bridge rectifier. The installation has been there over a year and has survived over a dozen op sessions with no ill effects. If a problem arose, I planned to add the dedicated supply or the extra wire, but since the DCC power has proven satisfactory I've just left it.
I understand the thinking this may not be an optimal way to run switch machines, but I think there's a lot of unwarranted worrying going on, especially about a test setup.
I see yes and I see no.
I have done ti to prove a point and it works fine.
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.
Maybe so, but there is no reason to do it even temporarily as long as a DC power source is available.
He wants to temporarily attach the bridge rectifier to his RAILS which has DCC power on them, then use the rectified DC voltage through a DPDT switch to TEST the Tortoise machine. NOT a permanent installation, just a quick way to use a readily available power supply (the track) to TEST the machines to verify their operation.
The responses have veered away from the original question at hand.
Remember, the OP asked about using bridge rectifier. He did not say anything about connecting the Tortoise directly to DCC.
Operating a Tortoise with DCC, VIA a bridge rectifier will work but a electrolytic cap on the output of the rectifier with the appropriate resistor for a minimum load would be advised for a steady DC voltage. That is the basis for power supplies operated by AC voltage.
As was said, the actual DC voltage would depend on the level of the DCC voltage.
Don't forget. ALL decoders have a full wave bridge rectifier with a filter cap in a DCC decoder. The DCC goes right to the input of the bridge.
Now would I do it, most probably not. As some have said, kind of a waste of DCC power.
A battery it is then. I still will use a DPDT switch so I won't have to reverse the connector every time.
Thanks guys,
73
Bruce in the Peg
A 9-volt battery is sufficient to operate a Tortoise to test it. That's a much simpler option, and you don't need to run long alligator clip leads from the top of your layout where the track is to the underside where you mount the Tortoise. Get the battery and one of those clips for it and you've got a complete self-contained Tortoise tester.
And, it will even work during a power failure.
Use DCC power for a Tortoise AT YOUR OWN RISK !!!
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.
Powering a tortoise permanently from the DCC track voltage is a bad idea. To cite just one reason, if you run into the turnout with the points set the wrong way, you'll get a short that shuts down the booster. Then you won't have power to switch the tortoise to the correct position. So you'll have to pull the loco and train clear before power restores and you can move the switchpoints.
For a test, use a 9 volt battery. For a permanent installation, use a wall wart (or two), wired using one of the methods in the Circuitron instructions:http://www.circuitron.com/index_files/INS/800-6000ins.pdf
Byron
It should be fine to do what you suggest as a test. It won;t overvolt the Tortoise. It will probbaly be a bit 'buzzy' sice the bridge will rectify but not filter the DCC, but it will not hurt the Tortoise. I wouldn't do something like this for a permanent setup, DCC track power is realtively 'expensive' compared to a simple 9V wall wart (I've found that below 6V, the Tortises are too slow) and should be used for powerinmg trains, not switch motors.
The 5 Volt DC output of an old computer power supply is even enough voltage for a Tortoise.
Since DCC is a high frequency AC square wave, it is not a good idea to connect a Tortoise to your DCC bus without a bridge rectifier. Even then, you're going to get some high frequency pulses to the Tortoise, which is not going to be good except for very short-term testing. The output of a bridge rectifier will be double the frequency of the input signal.
Basically I am only interested in operating one machine AT THE LOCATION of the machine to test it before connecting it to the system. I worry about the overvoltage more than anything else. I wonder what the max voltage is for a tortoise? I COULD use a series resistor if I relly need one.
That should work. I've heard of people running them on 9 volts all the time.
I guess I'm wondering why? A few would not be too big a deal, but more than a handful will add up to a significant drain on the DCC base. This is presuming that you're planning on tapping into existing DCC power.
There is a way to do this that's actually quite useful, but counts on additional investment. Buy an additional booster and dedicate it to operate turnouts. That way you have both turnout power and control separate from train power. It's sweet to be able to throw the switch to correct a wrong way move through a turnout, where a system configured as it typical is would require using the 0-5-0 to clear the short, then reset the turnout. If I ever run out of things to do and I still have some cash, I plan to update my own system like this.
Mike Lehman
Urbana, IL
Read the Tortoise instruction sheet carefully. It gives 3 options as I recall for powering the Tortoise.
I don't think that tapping the DCC bus wires is one of them.
It should work. The Tortoise only requires a few MA to operate.Some operate them at 9 vdc for more realistic operation of the points. I suspect it might buzz because the DC out of the bridge will be pulsing DC at the DCC frequency.
The bridge rectifier will drop 1.4 volts (0.7 volts perdiode). Not sure what the upper voltage limit is on a Tortoise, but if your DCC track voltage is around 16 volts, you'll be feeding about 14.5 volts to it .... which might be ok for a temporary test, but not a permanent installation.