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  1. BobK

    if there possible for pic to faulty?

    After you have been told twice, why are you asking again? Bob
  2. BobK

    need help with simple 3v to 34v transistor relay/switch

    From section 5.2 of the datasheet: So you simply clear the RBPU bit of the option register. In asm: BCF OPTION, RBPU Or in C RBPU = 0; Bob
  3. BobK

    Design question on microcontroller and TIP122

    A TIP122 is way overkill for a 250mA. You could use a 2N2222, it can switch up to 800mA. Assuming a gain of 100, you would need only 2.5mA to the base. I don't know what an 8051 can source, but it seems likely it could do that much. (or a MOSFET as Steve suggested, while I was typing in my...
  4. BobK

    String lights

    You could use a series of shift registers, and clock in a 1 at the beginning. It would ripple through all of them and eventually all lights would be on. So 8 8-bit shift registers + a 555 timer would do it. The biggest problem I see is all those wires. Bob
  5. BobK

    cree xm-l t6 bicycle light?

    From the looks of those lights, the case is the heat sink. Bob
  6. BobK

    cree xm-l t6 bicycle light?

    Thanks Steve, good explanation. Bob
  7. BobK

    UFO (undentified flat object)

    If it is an EL panel it would need 100V AC to drive. Based on the driver board, I think it might not be after all. Bob
  8. BobK

    UFO (undentified flat object)

    Electroluminescent panel. Bob
  9. BobK

    Is a voltage regulator always required?

    Let's see. You have a regulated supply. And you add a regulator. Now you have a regulated supply. Do you have to add a regulator to it? When do you stop? (No, you do not need another regulator if you already have a 5V regulated supply.) Bob
  10. BobK

    Motor controller circuit for 3hp pmdc motor

    You realize that what you are doing is illegal, right? Bob
  11. BobK

    cree xm-l t6 bicycle light?

    Here is the datasheet: http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/~/media/Files/Cree/LED%20Components%20and%20Modules/XLamp/Data%20and%20Binning/XLampXML.pdf The only thing I can find about thermal performance is: 2.5 C / Watt I have...
  12. BobK

    OP amp scaling voltage

    Yep, the AD8515 looks capable of doing what you want. I await the circuit. Bob
  13. BobK

    Question about Transformers and pulsed AC and DC.

    1 GHz ultrasound. I guess that makes microwave ovens an ultrasound device as well, at 2.45 GHz. I wonder if dogs can hear them? Bob
  14. BobK

    OP amp scaling voltage

    What op amp are you using and what power supplies? If the power supply is 0 and 5V, you will need an opamp capable of rail-to-rail outputs. If you are using and ordinary opamp you will need more like + and - 7V or more. Bob
  15. BobK

    Led Cube 8x8x8 problem

    Oh, wait. Of course it is multiplexed. By layer, I presume, so only 1/8 will be on at any time. So the current is more like 1.25 A. Bob
  16. BobK

    Led Cube 8x8x8 problem

    If you have 8x8x8 LEDs and they using the typical 20ma, that would require over 10 Amps to light all of the LEDs. But that does not explain why half the cube would light up, that is most likely a wiring error. Bob
  17. BobK

    if there possible for pic to faulty?

    .1uF is way to big for the capacitors in the crystal oscillator. Try 27pF. Or better yet, look up the capacitance required for the crystal, then multiply by 2 since the two are in series, and subtract maybe 5pF for stray capacitance. Bob
  18. BobK

    ADC pin draws much current?

    The ADC will only draw current when a sample is being taken. So, the way to deal with high impedance sources is to add a capacitor to ground big enough to supply the needed current when the ADC is sampling, and small enough to be fully charged by the sensor between sampling. This depends, of...
  19. BobK

    Solar Charging for Android Phone

    I just noticed the title. Android phone. I thought we were talking about an iPhone here. If the android phone has a removable battery, you have another option. That is to remove the battery from the phone for charging. This would eliminate the need for an additional battery. You could...
  20. BobK

    Solar Charging for Android Phone

    I doubt that there is a configuration that would allow charging at 80ma. I think your only hope to use that solar cell (the larger one) is to change an external battery as Steve suggested. You could trickle charge a battery made of 4 NiMH cells, then use this to charge the phone. If the...
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