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  1. BobK

    lowering voltage drop

    Sure there is, lower the current through it. The voltage across a forward biased diode is proportional to the log of the current. Bob
  2. BobK

    24 X 6 Matrix Display

    My calculator tells me it is $.04 each. :) Bob
  3. BobK

    how can i recording my analog data in my digital development board ?

    Oh right, missed the 30 FPS .:o Edited: Of course the OP has never told use how much he wanted to capture, could be a single frame. Bob
  4. BobK

    Common Emitter Transistor

    1. Use a P channel MOSFET with at gate threshold around 2 or 3V 2. Use a PNP and change to an open-collector comparator + pull up 3. Use and NPN and switch ground instead of V+ 4. Use a PNP and use and NPN as a level shifter to drive it's base. Bob
  5. BobK

    Re: 5 mm square LED. Solution needed.

    Solder them to a piece of perfboard with pin headers to go in the breadboard. Bob
  6. BobK

    turning off timer1

    Is the programmer connected? That pin is one of the programming pins and maybe the programmer is holding it low. Bo
  7. BobK

    Is this power adapter ok to use?

    I built my own NIMH charger to use with two drill-drivers that I had. They came with what was essetially a trickle charger, whch killed the batteries in about 1 year of light use. I learned about charging NIMH from sites like the one I posted above. To charge them correctly you need to detect...
  8. BobK

    Common Emitter Transistor

    The max output voltage of the LM324 will be V+ - 1.5V, so in this case 3.5V. So you have the emitter of the PNP at 5V and the base at 3.5V, which is enough to turn the transistor on. There is no way to turn it off when the base is connected to the output of the LM324, the voltage at the base...
  9. BobK

    Common Emitter Transistor

    Switching to a PNP will not do the trick without other changes. The LM325 can only ouput as high as V+ - 1.5V, so the PNP would be on even when the opamp went high. I would switch the LM324 to a comparator with open collector output and a pullup to V+. Bob
  10. BobK

    how can i recording my analog data in my digital development board ?

    The cyclone 2 is an FPGA with 68,416 configurable logic cells. It is likely capable of doing the job with configurable logic (not a cpu). It has a 256MByte RAM on the development board, so that would allow, by your calculation, for about 4 minutes of video. Now, whether the OP has the...
  11. BobK

    Is this power adapter ok to use?

    You cannot charge NIMH batteries just by connecting them to a voltage source. Read here. Then buy a proper charger for them. http://batteryuniversity.com/learn/article/charging_nickel_metal_hydride Bob
  12. BobK

    Charging Supercapacitor

    I think you could jump start your car from 5 of these in series. Bob
  13. BobK

    Two LED blinking

    Initially - input is held low by capacitor. + input is held higher by resitors, so output is high. This makes the + input at 2/3V+ via the resitors. (50K to V+ 100K to gnd) The capacitor then charges through the feedback resitor. Eventually the - input exceeds the + input and the output...
  14. BobK

    Charging Supercapacitor

    Wow, charge and discharge at 600A in 0.3 seconds. Bob
  15. BobK

    first kit, slight problem :-(

    Yes, a smoothing capacitor is a low pass filter. Ideally it will pass only 0 frequency, i.e. DC. On a synth, filters are used to shape the audio waveforms by suppressing different parts of the audio spectrum, so the purpose is a little different. For instance a triangle or sawtooth waveform...
  16. BobK

    AC Electromagnet

    But can I have one that is hand-held? Bob
  17. BobK

    Chronograph for bullets

    I don't understand why you want to debounce. This adds an unpredictable delay to the signal. For the most accuracy, you want to trigger as soon as possible after the connection is broken and ignore any bounce. Essentially you have 3 states: 1. Ready - both wires intact, counter is zero...
  18. BobK

    Power source

    In this post, it sure looks to me like you interpreted his 0-10V control voltage as the power input. Bob
  19. BobK

    Is there any different using two power supply?

    Didn't realise "mbed microcontroller" was a specific term. Thought he just meant "embedded microcontroller" Bob
  20. BobK

    Power source

    C.C., To be fair to the OP, he stated a "0-10V dimming input." I did not read that as being the power input as you did. Bob
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