I should know this but I am too lazy from all that Christmas food[:D]
In order to test the operation of any Tortoise, I plan on a pair of allegator clips wired to a full wave bridge, a DPDT toggle switch, then to the tortoise. If I connect the clips to the rails, is there sufficient voltage to actuate it? The IR drop of the bridge is ~2 volts I assume.
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.
Mark.
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.
Rich
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.
Rich
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.
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.
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.
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.
–Randy
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
[tdn] Use DCC power for a Tortoise AT YOUR OWN RISK !!!
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.
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,
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.
Rich
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.
Mark.
Maybe so, but there is no reason to do it even temporarily as long as a DC power source is available.
Rich
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. [banghead]
Mark.
I see yes and I see no.
I have done ti to prove a point and it works fine.
Rich
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.
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.