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  1. BobK

    Need Transistor to relay help ASAP

    CC, It's great to have an interpreter that speaks newbie :) Bob
  2. BobK

    Need Transistor to relay help ASAP

    I don't understand your question. Pin 4 connects to the center lug on the pot. Pin 5 connects only to the thorttle control. When lines cross, there is only a connection when there is a dot there. Hope this is what you were asking. Bob
  3. BobK

    Need Transistor to relay help ASAP

    That was one reason I suggested the LM339. I believe they carry them. Bob
  4. BobK

    Using a transistor as a relay

    Yes, it could be replaced by an Intel Core i7 :) Bob
  5. BobK

    Need Transistor to relay help ASAP

    The - can be considered the reference and the + as the input. The comparator does not follow the voltage, it is a descriminator. Think of it as a switch, it connects the output to ground whenever the - input is > the + input, and it disconnects the output from anything when the + input is >...
  6. BobK

    Need Transistor to relay help ASAP

    Here is a schematic of a transistor switch controlling a relay using a comparator to set a voltage threshold. The pot can be adjusted to set the voltage between 0 and 12V, so 6V should be very near to the center. Or you could use fixed resistor in the ratio of 3:1 (top:bottom) to get a 6V...
  7. BobK

    Need Transistor to relay help ASAP

    Here is a discussion of the schmitt trigger, which is a 2 transistor circuit that can function as a comparator. Bob
  8. BobK

    Need Transistor to relay help ASAP

    No, as CC keeps telling you, you cannot simply use a resitor. Transistors do not turn on or off instantly at a particular voltage or current, they are linear devices that will partially turn on at a voltage less than the threshold and this is dependent on the particular tranistor (even of the...
  9. BobK

    Near signal detector

    But I just love the thought of a turtle cop car! A blue flashing LED would be so cool! Bob
  10. BobK

    Need Transistor to relay help ASAP

    A comparator is an IC that will compare one voltage to another and output a signal depending on which is larger. So you would feed 6.0V into the - input and the throttle output into the + input. This would turn the comparator on when the throttle voltage exceeds 6V. The "standard" compare is...
  11. BobK

    Near signal detector

    How about a blinking high brightness LED on the turtle's back? Bob
  12. BobK

    Need Transistor to relay help ASAP

    That is not correct. Aside from the fact that the relay coil is not in the circuit, the transistor is backwards, and is shorting supply to ground if it turns on. The correct way to wire a an NPN transitor to turn on a rely is: C to one relay coil lead other relay coid lead to V+ E to...
  13. BobK

    Near signal detector

    The size and power requirements for the receiver. I am guessing that they are not especially small and low power since they are intended to by mounted on a wall in the house. Bob
  14. BobK

    Near signal detector

    I must be dense or something, but I don't get how a remote doorbell solves the turtle location problem. Does the turtle carry the receiver and you press the button and locate him by the sound? This seems rather impractical. Bob
  15. BobK

    Creating a different kind of hearing aid for my dad.

    That looks like exactly what OP is looking for! If it is discontinued that would be a shame. Bob
  16. BobK

    Running an LED off a 120v wall outlet

    But the high quality lights have a 20W halogen with reflectors and columnators, which makes them at least as directional as an LED. This is why I think you need reasonable high power especially at high magnifcations. Do a search on for microscope illumination products, you will see what I am...
  17. BobK

    Running an LED off a 120v wall outlet

    That looks good, but you might want to try something less powerful to start with in case Coca Cola is right an I am wrong. I would hate to think that my advice burned a hole in your eyes! Bob
  18. BobK

    Creating a different kind of hearing aid for my dad.

    Coca Cola, Are you sure that is the right link? All I see is something that allows you to charge 6 devices at once, not combine multiple audio signals. Bob
  19. BobK

    My Power Supply Saga

    I think his circuit would try to make ground = 1.25V, which means it would just open up the pass transistor fully. Bob
  20. BobK

    Running an LED off a 120v wall outlet

    The LED ones I found were also in the hundreds of lumens. The professional grade lights have columnators. What you are seeing in the microsope is a microsopic part of the beam coming out of the light, blown up to look like it is several inches across. It is not equivalent to looking at the...
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