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  1. BobK

    Digital calendar which flashes a LED when out of date range

    It will if you charge it every night! Bob
  2. BobK

    Digital calendar which flashes a LED when out of date range

    The simplest and cheapest way is to write an app for you cellphone. Bob
  3. BobK

    efficient batteries.. help!

    Seeing as Lithium batteries are by far the most efficient that are practical today, the limits you have placed on materials makes your project impossible. Now, if you lived in Victorian times, you might have been on to something. Bob
  4. BobK

    Electromagnetic Fields

    It sounds to me like you are reading material that is beyond your knowledge. You understand the terms they are using, so you come and ask us. You need to start with a basic text on electronics and learn things one at a time. Bob
  5. BobK

    Does electron die?

    The current in an RC charging circuit decays exponentially. The time constant (RC) tells us how long it takes to charge up to 0.632 of the voltage it is charging from. Each time constant takes it this same proportion from the existing voltage to the final voltage. 5 is an arbitrary number...
  6. BobK

    Detecting positive and negative edges

    And create negative pulses that you would have to suppress. It simply does not help you at all. The edges coming out of the other micro should be pretty clean already, but I was suggesting you use a Schmitt trigger input on the micro if one is available. The capture feature that Minder...
  7. BobK

    12V adapter + resistor = 9V adapter?

    Alec_t, He is running it off a 12V adapter, not a battery. Bob
  8. BobK

    Does electron die?

    There you go! Bob
  9. BobK

    12V adapter + resistor = 9V adapter?

    Use a 7809. Here is a link to the circuit. http://www.harrington.jp/diy/simple-9v-voltage-regulator-circuit/ You probably do not need the capacitor on the input, but on the one on the output is important. Bob
  10. BobK

    Does electron die?

    That is because you are simulating 9000 seconds. The capacitor is fully charged in about 20mS. Try 20m for the simulation time (20 milliseconds.) Bob
  11. BobK

    Complete electronic virgin!

    Just knowing how fast you are approaching an object and the distance to it is not enough. Consider a car going around a curve on a road lined by trees. Any prediction based on the instantaneous velocity (not speed) of the car will predict that it will hit a tree at any time! And the trees are...
  12. BobK

    Does electron die?

    LTSPICE calculates a stable starting state before taking data. The stable state has the capacitor completely charged, so you don't see the exponential fall in current which actually happens. To see that, you need to check the box "skip initial operating point solution" box on the "Transient"...
  13. BobK

    Detecting positive and negative edges

    I don't know why you need a differentiator. That would give you a positive going pulse at the start and a negative going one at the end. The microcontroller can detect the edges itself without a differentiator. And in fact, it would not like the negative going pulse at all. In PIC...
  14. BobK

    Circuit Help :) - LDR LED Cube (Urgent)

    That is some creative circuitry. I especially like the way the relay shorts the power, and the power and ground for the 555 and sensor circuit are routed through reverse biased LEDs. I would have never thought of either of those. Also, honorable mention for the two redundant inverters between...
  15. BobK

    Does electron die?

    Actually, I thought I did say that, but I am not up for reading that thread again, or resurrecting it. The only way I could make what others were saying true was to substitute "Ohms Law" with "some relation between I and V, but it may be non-linear and depend on other variables such as time...
  16. BobK

    Complete electronic virgin!

    I hate to tell you this, but this would be a major project requiring many engineers over a period of years to perfect. Why do you think cars have only incorporated anti-collision systems over the last few years? Bob
  17. BobK

    help with heat sink

    Also consider: not all of the power is lost in the transistor. Could will be some in the inductor, and possibly in resistors. Bob
  18. BobK

    Does electron die?

    Here is the thread. Be prepared to be dumbfounded. The basis is this quote: I disputed this, thinking it was non-controversial, and got basically no support for my position. https://www.electronicspoint.com/threads/ohms-law-or-not-ohms-law-that-is-the-question.252367/ Bob
  19. BobK

    Does electron die?

    It has nothing to do with linearity. Ohms law describes the relationship of voltage to current in a resistor. There are other equations (laws) that define the relationship of voltage and current in other components. For example: dV/dt = I / C for capacitors dI/dt = V / L for inductors Bob
  20. BobK

    Does electron die?

    No. Bob
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