LED With Circuitron Tortoise Switch Machine

Hytec Jul 18, 2018

  1. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    I want to install a bi-polar (Red/Green) LED with a Tortoise switch machine. Since the Tortoise requires voltage, positive or negative, to be supplied continuously to keep it in position, wiring the LED in series in one leg should show red or green depending on polarity. Also wouldn't the internal resistance of the Tortoise protect the LED from over-current? Or should I wire the LED in parallel with the Tortoise, and with a resistor to protect it?

    Is my thinking correct? Has anyone done this?

    Thanks.
     
  2. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

    4,696
    1,381
    70
    Hank, yes, what you are thinking works just fine with a Tortoise. It is even shown in the instructions (diagram 4 of the wiring diagram). Wiring in series with bi-polar, no additional resistor needed. Just note that in this method, you are reducing the voltage to the tortoise motor by the forward voltage of the LED.
     
  3. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    Thanks, the LEDs I'm looking at drop about 2 volts. Tortoise instructions specify 9-12 volts. I plan to use a left over (junk box) 12vdc 500ma power source from something long ago forgotten. So 10 volts nominal should work fine for activation. I'm installing 12 Tortoises which should draw less that 200ma when all are stalled. The instructions don't mention activation current, but I can't imagine it being anywhere near 300ma.
     
  4. lexon

    lexon TrainBoard Member

    1,025
    10
    22
    A Tortoise draws 20 ma when stalled.

    Rich
     
  5. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    Thanks Rich. At 240+/- ma stalled current for 12 machines, I must rethink my power source. I can visualize flipping 3-4 switches at once to establish a new route. This could demand as much as 1.5 A during activation. I had never used Tortoise machines, but now see that they take 2-3 seconds for full throw. Don't get me wrong, they're marvelous machines and versatile in mounting options, just a little finicky to get correct throw rod action with an offset mounting.
     
  6. Jimbo20

    Jimbo20 TrainBoard Member

    169
    145
    6
    The application sheet states that the stall current is 15-16 mA, and the operating current would be less than that as the sheet states that the series connected LEDs go dim during the actual throwing of a switch. Their application sheet also suggests that a 12v 500mA wall plug adapter will power 30 devices....
    http://www.circuitron.com/index_files/INS/800-6000ins.pdf
     
  7. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    Thanks, Tortoise's application sheet is what I was basing my original design on. However, Tortoise's statement that series LEDs go dim during operation indicates that operating current demand is more than stalled current demand. I agree that a 500 ma supply will handle 30 machines at 16 ma in stalled conditions. However, Rich's measurement of ~20 ma demand for stalled condition, and Tortoise's avoiding disclosure of operating current demand are disturbing, especially when I consider operating 3-4 machines at the same time. I'll measure operating current demand before I finalize my design.
     
  8. Jimbo20

    Jimbo20 TrainBoard Member

    169
    145
    6
    IMHO the fact that the LEDs go dim imply that the current reduces during operation (they are in series with the motor), and then when the motor stalls at the end of its travel, the current rises so the LED goes bright again.

    EDIT: Indeed this page confirms it:
    http://www.circuitron.com/index_files/tortoise.htm
     
    Last edited: Aug 14, 2018
  9. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    Thanks for your research. That makes sense because a stalled motor draws more current than an operating one due to back-EMF developed by the rotating armature.

    However, I question Tortoise's values. I pegged my multi-meter on the 300 ma range for both the stalled and operating states. Unfortunately I don't have access to an ammeter with a higher range. Also this may explain why I was draining a 9V battery after only 10-12 activations. Though it's possible that my 40+ year old multi-meter is finally giving up the ghost. :eek:

    Perhaps someone has convenient access to a Tortoise and an ammeter with a 1-5 Amp range, who can measure currents for the two states?
     
    Last edited: Aug 14, 2018
  10. lexon

    lexon TrainBoard Member

    1,025
    10
    22
    The LED did not burn out so I was not concerned. The total current passes through the LED.

    Rich
     
  11. Jimbo20

    Jimbo20 TrainBoard Member

    169
    145
    6
    Indeed - if >300mA was passing through the LED, the LED would be no more!
     
  12. lexon

    lexon TrainBoard Member

    1,025
    10
    22
    It would not take too long to drain a battery but I am curious, how did he hook up his meter to peg it? If the meter was in series like the LED, it should not peg on the 300ma scale.

    Rich
     
  13. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    I agree with both of you, though my Rail Power 1370, set at 11 Volts, hums when the Tortoise stalls which concerns me. A hum usually indicates high current draw. Gotta find a reliable ammeter. :unsure:
     
  14. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    I agree, but the meter was in series. I'll hook it up and measure again just to verify.
     
  15. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    OK, having acquired a new, and digital, meter, I now have hard evidence that the Tortoise works as advertised. The stalled current was 14.5+/- ma. Operating current was 4.7+/- ma. So all is right with the world.

    Now to solve why this 12th and last machine won't throw the single point of a trolley turnout to the full straight position. The point appears to stop at a slight blockage. When I lightly touch the point with a screwdriver blade the point pops hard over to the stock rail. I cannot detect any blockage to the point movement when I remove the machine and its spring wire. Of course it doesn't help that I had to mount the machine way offset from its center line. Though the three other machines mounted in the same way have no problem. Throwing to the point's curved position works every time.

    OK, I'll admit I am venting frustration. Though I'm open to any suggestions because nothing I've tried has worked.

    EDIT: Shh, don't anybody say a word or you'll jinx it, but the point has started to work. There's a slight hesitation before it pops into the straight position, but it's hard against the stock rail. I guess all I had to tell it was that I was asking experts for advice. So it decided to get its act together. Ain't the Trainboard a great place!! LOL
     
    Last edited: Aug 14, 2018
  16. lexon

    lexon TrainBoard Member

    1,025
    10
    22
    Well, that is good troubleshooting. I keep more than one meter around, having worked in electronics for fifty years. I now use Harbor Freight multi-meters and a couple O scopes. I have four meters as it is easy to misplace a meter. My D'Arsonval meter died maybe twenty five years ago. I built it as a kit about 1955.

    Rich
     
  17. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    Rich, the meter that died also was a D'Arsonval movement. I assumed it would live forever because it was mechanical, having replaced an earlier Heathkit digital unit from the mid-fifties. Ah well, I guess nothing lives forever. PS, I love troubleshooting. I assume that man's brain can analyze and overcome most everything nature can throw at it, except maybe for the dolphin species, including Orca, the ultimate dolphin.
     
  18. lexon

    lexon TrainBoard Member

    1,025
    10
    22
    Interesting enough. Mine was a Heathkit D'Arsonval movement I soldered together along with a AR-3 shortwave receiver.
    I forgot about a HP VTVM I bought at a NASA facility auction where I worked as a contractor but gave it away when I moved. That was quite a meter. A huge D'Arsonval movement. But moving off topic.

    Rich
     
  19. RBrodzinsky

    RBrodzinsky Staff Member TrainBoard Supporter

    4,696
    1,381
    70
    Hank,

    Look for something (usually debris) restricting the points or the throw bar movement. And, make sure the throw bar has no vertical movement. And sometimes the debris is up the point rail / stock rail, and not right next to the point.
     
  20. Hytec

    Hytec TrainBoard Member

    10,929
    1,029
    130
    Rick, you probably are right on point. I won't go into details, but this being my first experiment with 6.125" radius trolley rail, single point turnouts, ultra-cheap hollow core door disasters, and single point turnouts with long throw Tortoise machines, this has been a massive learning experience. But, Hey, that's what our hobby is all about, right? I may be a challenge, but I'm having a blast.
     

Share This Page