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  1. BobK

    Dewalt Charger Circuit

    Typically the chargers that come with battery powered tools are trickle chargers, nothing more complex than a transformer, rectifier and series resistor. Bob
  2. BobK

    using wal wart to make variable voltage power supply

    Ohms, Amps, what's the difference? Bob
  3. BobK

    Trying to build my first circuit

    Okay, now I understand. The output has to be a + or - signal. And if I go from 1st to 3rd it would output two + pulses, for example. The problem I see with this is that the current state has to be kept in two different places. One inside the X-box controller and one in your add on. If...
  4. BobK

    help with semiconductor

    diac, silicon controlled rectivier (SCR), programmable unijunction transistor (PUT) can all perform this function. However, you are probably better off with a circuit involving a comparator and a MOSFET. This would be more accurate and flexible. Bob
  5. BobK

    Best cheap MCU for LED project

    I know only PIC microcontrollers, so I can give you info only about them, there may be others that are cheaper. So you need 1 input and 3 outputs. A 6 pin PIC could do the job. Partly it depends on how good a programmer you are. The PIC10F series are 6 pin PICS and range from $0.31 o...
  6. BobK

    4 photo-interrupters in my circuit

    You do not need to limit the current of the sensor. The Icc parameter is telling you the max current it will draw when connected to anywhere between 4.5 and 16V. You just need a power supply that can supply this much current. You do need a pullup resistor on the output. If these are...
  7. BobK

    Trying to build my first circuit

    If you have 6 switches, one for each position, what is the point of adding or subtracting? Each switch determines which position the shifter is in, without needing any knowledge of where it was previously. Bob
  8. BobK

    Making 100 leds flash?

    No. That is exactly figure 2.2 from the tutorial, the one it says "Do Not Connect LEDs in parallel". You want either 2.1 or 2.4 depending on your supply voltage and the forward voltage of the LEDs. Bob
  9. BobK

    prototyping PCB boards

    I find that stripboard is very good for prototypes, produces very neat boards with a little effort. The only drawback is that you will not get great component density. There is free software out there to help layout stripboard from a schematic, but I am at work now and don't remember what I...
  10. BobK

    using wal wart to make variable voltage power supply

    Did you really mean 24V at 3 Ohms? That would be 8 Amps. Also, that must be one massive wall-wart if it outputs 31.5V at 3.17A. Bob
  11. BobK

    4 photo-interrupters in my circuit

    Look at the If(+) parameter and note 16 on page 5. It specifies that the LED current for detection must be > 15 mA. The datasheet also lists the forward voltage as 1.7V at 20mA, so that is probably the normal operating current. You should have a current limiting resistor for each detector...
  12. BobK

    The magic of Colloidal silver

    The article you linked does not mention "colloidal silver" as a remedy for anything. It is about using silver ions to enhance the effect of antibiotics. It also says that it is toxic: And here is info from the Mayo Clinic: http://www.mayoclinic.com/health/colloidal-silver/AN01682...
  13. BobK

    The magic of Colloidal silver

    The article you linked does not mention "colloidal silver" as a remedy for anything. It is about using silver ions to enhance the effect of antibiotics. It also says that it is toxic: Bob
  14. BobK

    What kinds of Op Amp should I use?

    Being cryptic does not help to get your question answered. Why don't you tell us what these 2.7V sources are and what you are trying to do with them? Bob
  15. BobK

    The magic of Colloidal silver

    If you think the placebo effect works only on symptoms that are "in your head', you don't understand it. Most of the placebo effect is attributable to that fact that any subjectively reported symptoms vary up and down whether you are taking medication, a placebo or nothing. This is why placebo...
  16. BobK

    lighting a 7 segment LED

    This is your problem. All of the current for all segments is going through this one resistor. The more segments you enable, the higher the voltage drop in this resistor and the lower the voltage each segment will see. You need to take out this resistor and place a separate resistor between...
  17. BobK

    High Power LED PWM

    As Steve implied, you power supply is a bit weak for a 700mA 3.6V LED. Are you trying to make a flashlight? This site has lots of very inexpensive parts for doing so. Deal Extreme Bob
  18. BobK

    dumy load question

    12V auto lamps make pretty good power resistors. Use at least 2 in series for a 17V source. Bob
  19. BobK

    Making 100 leds flash?

    Easiest would be 1 N-channel MOSFET for 1 set and 1 P-channel MOSFET for the other. Bob
  20. BobK

    What kinds of Op Amp should I use?

    What are you trying to do? I suspect you are trying to step up a 2.7V power source to get 16V. For this, you need a boost converter. Bob
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