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  1. BobK

    Maximum voltage generated by a function generator

    I think what it means is that the voltage is 10V with an internal resistance of 50 Ohms. If you measure it with a 1M probe it would read 10V. If you put a 50 Ohm resistor across the output, the voltage would be cut exactly in half. Bob
  2. BobK

    seeking some advice/knowledge relating to RF communication

    Maybe this is a stupid question, but is there reliable cellular service in the area? Bob
  3. BobK

    How to increase voltage?

    Sorry, I do not speak TLA. Bob
  4. BobK

    How to prevent a capacitor from dischargeing back into my circuit?

    Hmm. You've got a point there! Bob
  5. BobK

    How to prevent a capacitor from dischargeing back into my circuit?

    Charge the cap through a diode from a PIC pin. The diode will prevent it discharging though the protection diodes in the PIC. When the PIC resumes, the pin will be an input and you can measure the voltage before setting it to an output. I.e. PIC pin to anode, cathode to cap, other side of...
  6. BobK

    Non-changing current with C-EMF

    Because you are not using the correct voltage across the resistor. The voltage is the voltage from the constant current source (2.0042V) plus the counter EMF of -2V for a net voltage across the resistor of 0.0042V. If the current through a resistor of R Ohms is I Amps, the voltage across it...
  7. BobK

    5V AC adapter in place of 3V AC adapter?

    Did the fan actually come with a USB connector on it for power, or did you put that on it? Do you have a link to the fan? Bob
  8. BobK

    Darlington Pair Touch Switch meets Edward Holmes' Toy Piano

    There was a video of a guy (Russian) who build a keyboard using coins as capacitive touch sensors using just a PIC6F84, an old, not very capable 18 pin PIC. It was polyphonic and he played an amazing demo on the video. Now that is a touch keyboard project! I just spent 15 minutes looking and...
  9. BobK

    Non-changing current with C-EMF

    You You calculation is wrong. To maintain current of 1000A across the resistor will always have the same voltage across the resistor. The back EMF is not added to the voltage needed without back EMF. This is what is causing your massive power. In the presence of -2V counter EMF, the...
  10. BobK

    Transistor spice model

    Are you designing your own transistors? Otherwise, get the model from the manufacturer. Bob
  11. BobK

    Plotter machine from old CD/DVD drives

    When I said 2 positions, I meant pen up and pen down. Yes, this is a Z axis, but it does not have to be a range, just up and down. Bob
  12. BobK

    How do LDRs work?

    Have you tried Wikipedia? http://en.wikipedia.org/wiki/Photoresistor Bob
  13. BobK

    Plotter machine from old CD/DVD drives

    Pretty cool. Once you get Z working (for a plotter you really only need 2 positions, no?) I would like to see if you could make a PCB by using a resist ink pen and drawing on the copper. Bob
  14. BobK

    1w vs 3w LED running at 1w

    You might also find that the 3W LED operated at 1W produces more light than the 1W LED. Check the respective datasheets. Bob
  15. BobK

    Cheap alternative to graphic LCD, OLED & TFT displays modules

    Unless, of course, you want to buy 1,000,000 of them. Bob
  16. BobK

    Make your own non-inverting Schmitt Trigger

    You can make a Schmitt trigger from an op amp or comparator by utilizing positive feedback. Here is an example (scroll down to get to it) http://www.talkingelectronics.com/projects/OP-AMP/OP-AMP-2.html Bob
  17. BobK

    how i rewrite a microchip

    You do realize that microcontrollers can be had for less than 1$. Trying to salvage something and reuse is a total waste of time. And, even if those motors are stepper motors, they are unlikely powerful enough for a 3-D printer. Bob
  18. BobK

    motor control using FDMF5821DC

    Yes. It is also possible to use an electric drill as a hammer. Bob
  19. BobK

    Solar Powered Phone Charger

    You have been told what you need several times. No one of said you needed an inverter. I will tell you once again, what you need, this time more explicitly. 1. A solar panel outputting 5W at greater than 5V. 2. A DC-DC converter (buck converter) that can handle the input from the solar...
  20. BobK

    Help choosing a capacitor for a toy

    Adam, At what current? I have not seen any post that specified the current it uses. Bob
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