Mech/Elec Qs reg. Tortoises

[FJ and G]

Bought a 6-pak & read instructions. AC is allowed but only up to 12V. My V=18. Guess I need to place some resistors inline? I could use DC but want to use track power, making a non-derailing type. Yes, 3 sec is long but plan to extend the insulated rails. Any ideas?

Second Q not as important. Considering a 3-way switch using Tortoise power. Can it be made to index to 3 locations?

Any other tips or tricks appreciated. BTW, using for my handmade track.

Thanks.

Dave VErgun

[lionelsoni]

Dave, I was sure that tortoises use DC can motors, with the polarity determining the direction of travel. Do you have some new, different model?

If your tortoise is DC, as I suspect, you can run it on half-wave-rectified 18 volts AC, which has an average DC voltage of about 8. Simply return it to the 18 volt terminal and put a rectifier diode in series to each isolated rail, each with the polarity that drives the tortoise in the appropriate direction.

I have made a tortoise go to 3 positions, using the built-in electrical switch to determine the middle position. It is not very precise, but good enough for a Marx semaphore. Whether it would work for your switch, I don't know. What sort of switch is it?

[FJ and G]

Bob,
Forgot to mention that instructions recommend 2 diodes inline. THanks for the other info. I'll play with it for a while.

[lionelsoni]

Dave, I just dug out the tortoise data sheet and saw what you described.

I experimented with an idea that may make your anti-derailing application work better: Wire the tortoise as I described above, with diodes to each of the isolated rails from the same side of the tortoise motor, but add a 10 microfarad capacitor in parallel with the motor. This will boost the DC motor voltage (which is related to speed) to something like 16 volts while it is running, but will allow it to drop to a safe level, around 12 volts rms (which is related to heating), when it stalls. So the switch will throw significantly faster without any harm to the motor. I tried it out and it seems to work.

The capacitor must be a non-polarized type, not a conventional electrolytic. The capacitance must be close to 10 microfarads to get the desired behavior, rated about 25 volts minimum.