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  1. BobK

    Measurement device

    Would you please clarify what you are trying to do? Both Kellys_eye and and Duke37 seem to think you moving something along the tape. My interpretation is that the tape simply sits there and you press it at various spots. The solutions are entirely different. Bob
  2. BobK

    Bypassing TV's internal speakers to home-made aux input

    Probably true if you are talking about high end equipment. For this application, not so much. Bob
  3. BobK

    Measurement device

    I am trying to decode what it is you are trying to do. If I understand you, you have a linear measure, marked as usual, and you want to be able to press at various marks and get a output that encodes the position at which it is pressed. If that is correct, what you need is a linear membrane...
  4. BobK

    T8 - LED shop lighting

    Any claim of lifetime should include the level of degradation. e.g. 50,000 hours at 70% output. Bob
  5. BobK

    Bypassing TV's internal speakers to home-made aux input

    There is a way. You would need to use an audio isolation transformer between each speaker output and the headphones. After the Isolation transformer, you can connect one wire of each to form the common without shorting the wires from the speakers. Here is an example of what I am talking...
  6. BobK

    Bypassing TV's internal speakers to home-made aux input

    The outputs are probably bridged, which means neither of the wires are at ground. When you connect both channels to RCA jacks, you are shorting two wires together since each RCA jack has one side going to ground. Bob
  7. BobK

    Foam cutter,load

    Before you go gung ho. Here is a site that has all the info you need to design your foam cutter: http://hotwirefoamcutterinfo.com/_NiChromeData.html You need to choose the wire diameter and current to get to the correct temperature. According to that site, about 600F is good for cutting...
  8. BobK

    Foam cutter,load

    It won't offer well controlled current, it will deliver a PWM signal. That should be OK for heating a wire. The wire should have the correct amount of resistance to act as the load. For 2A at 12V the resistance is 6Ω. Bob
  9. BobK

    Component

    When adjusted properly, this will tell you whether it is seeing dark or light beneath it. You would need two of them, side by side, to make a line follower. Assuming it is following a dark line on a light background, when the left one detects light, you turn a bit to the right, when the right...
  10. BobK

    Need help, regarding LED circuit

    If you look below, it lets you pick the size, color, and quatity. If you pick 10mm, white, and one, then press “buy it now”, the price is £1.99 Bob
  11. BobK

    Finding a nano amp transistor for Solar LED Light Marker

    The comparator does not help you with the low voltage for charging, it allows you to switch the LED with a low voltage. Yes, even 9mV. Bob
  12. BobK

    Need help, regarding LED circuit

    They are not cheap. £1.99 for 1 LED and resistor! You could get 100 for that price. Bob
  13. BobK

    Finding a nano amp transistor for Solar LED Light Marker

    You would need a comparator with rail-to-rail inputs and outputs. If your LED is on the order of 20mA or less, you could drive the LED directly from the comparator. The booster would have to be turned on by another transistor from the comparator output. Bob
  14. BobK

    Beginner looking for a specific component

    I think you mean an DPST switch, basically two switches side by side, operated by one toggle. DPST - double pole single throw. i.e. two switches switching something on and off. Bob
  15. BobK

    Compilers

    Microchip also provides free versions of their C8, C16, and C32 compilers for their 8, 16, and 32 bit processors. I use these and I am happy with them. Bob
  16. BobK

    Please help to buy those components

    First, get a component tester that can measure inductance: Component tester Get a 10 cm by .5 cm ferrite rod: Ferrite rod Get some magnet wire, 30 ga: Magnet wire Wind the primary on on end of the loopstick, checking with the component tester until the inductance is what is called for...
  17. BobK

    Please help to buy those components

    Is not a radio circuit? I build a TRF radio using MK484 which is pretty much the same thing but 3 stages all in a TO92 package to tune the local station that broadcasts the Red Sox games. It can separate the signal from a very strong station nearby, though I have to turn the antenna to null...
  18. BobK

    Please help to buy those components

    So, now are you telling us the book DOES tell you how to construct the antenna coils? And, by the way, that is what I meant by a ferrite rod. Bob
  19. BobK

    Bone conduction low frequency speaker

    If you really want to rattle you brain: Bass shakers Bob
  20. BobK

    Please help to buy those components

    In that schematic, the two coils on the left are almost certainly to be wound on a ferrite rod and make up the antenna for the radio. If the book does not tell you how to wind them, then it is useless. I don't believe they can be wound on a toroid because that would not make an effective...
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