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  1. BobK

    help with power consumption.

    There must be a voltage and current rating for the motor. The power is the product of the two. Bob
  2. BobK

    detecting low voltage with PIC

    The 1K is only there to limit current if both ports accidentally become outputs. That would limit the current to 5mA which is well within their sink / source capability. When you have a long cable, a voltage can be induced in the cable by your AC power for example. The voltage can be high...
  3. BobK

    Generating Multiple Frequencies

    I have no idea how one generates -100 frequencies. Does this involve time reversal? Bob
  4. BobK

    detecting low voltage with PIC

    Assuming this is not going through a long wire, you can connect them directly. The only caveat is that a programming error could have both pins as outputs and at opposite logic levels, perhaps destroying that output drivers in the PICs. To prevent that, use a resistor on the order of 1K...
  5. BobK

    Voltage regulation

    And whether you want things getting hot or not. Dropping 7V at 200mA is 1.4W of power, enough to need a heat sink if a linear regulator is used. Bob
  6. BobK

    pull down resistor for npn relay driver

    10K would typically be fine. It is not critical. Bob
  7. BobK

    detecting low voltage with PIC

    Yes, you can connect an input of one PIC to an output of another PIC. Bob
  8. BobK

    Electric motor to turn a fishing reel

    Well, what you really need to do is determine what speed (or range of speeds) in RPM that you want and how much torque is needed, what power supply, then buy a geared motor that meets that specification. Bob
  9. BobK

    Generating electricity from cell phone tower transmissions

    Seeing as the cell phone transmissions are microwaves, why not use them to cook your food? Bob
  10. BobK

    Relation or difference between Input clamp current and Sink current

    You are looking at this spec: That is the ability of an output port to act as a ground to a current coming in. For instance, if you were trying to run an LED by connecting it to V+ and to the port which is set low, it would only be able to handle 2mA. The one you are interested in is this...
  11. BobK

    Help with 555 timer circuit

    An 8 ohm speaker on the output of a 555 should certainly produce a sound, and quite loud, assuming the 555 is oscillating within the audio range. 200mA is just the max current the chip can output, when loaded higher the voltage will drop, but it will not stop completely. I cannot explain what...
  12. BobK

    Effectively defeating PWM on Jeep Wrangler

    Agree with JW. The only way to do this right and keep the high / low beam behaviour is to convert the PWM to a higher frequency. It is doable, but would involve some level of skill. Simplest, hardware wise, would be to use a microcontroller. Bob
  13. BobK

    How to slowdown capacitor discharge

    Or, you could run the LEDs directly off the AA batteries and get about twice the life out of them. Converting to a higher voltage then converting to a lower voltage loses energy in both directions. If you studied physics, you would know before you try. You cannot get energy out of nowhere...
  14. BobK

    How to slowdown capacitor discharge

    Don't waste your time. The Bedini motor is yet another impossible perpetual motion machine. It does not work and anyone who claims it does is lying, probably to get some money out of you. Think about it. If any of these things was actually real, wouldn't all have them running our homes and...
  15. BobK

    Relation or difference between Input clamp current and Sink current

    Don't know where you got 2mA for the the input current. Looking at a datasheet for a similar PIC, i see that the input current is ±100nA. 2mA is ridiculously high. The parameter is called "input leakage current". What was the name of the parameter that gave you 2mA? Bob
  16. BobK

    Can someone help describe how this circuit works?

    Based on the notations on the diagram, I would say that it it sounds an alarm when the the loop is broken. But there is a delay after turning it on (exit time) and after the loop is broken (Entry time). So, you switch the alarm on, have so much time to go through the door, then it arms. If...
  17. BobK

    How to detect very high frequency sound ?

    Please tell me that this is not to detect ultrasonic waves that someone is beaming at you for nefarious purposes. Bob
  18. BobK

    Cheapest way to get data from multiple(100s) of sensors?

    Alright, we have collaborated for what I think is a good design! Bob
  19. BobK

    How to slowdown capacitor discharge

    I suppose it is possible that the short cranking provided all the energy to run that motor for that long. But that is a very small motor. On the other hand, there are so many fake videos out there, I do not trust any of them. If you want to no how much effort it takes to produce useful power...
  20. BobK

    How to slowdown capacitor discharge

    One way to look at is is energy conservation. Say you have two capacitors of 1F each. Each is charged to 10V. The amount of energy in these two capacitors is then 1/2 * 1 * 10^2 or 50 Joules each, so 100 Joules total. If you put them in series, there would be 20V across the two capacitors...
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