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  1. (*steve*)

    What's so special about mini-MELF 1N914s?

    I have 1000 of them. Anyone want to offer me $US1000? :-D Should I tell you they cost me under $5? I will make sure I get my boards gold plated when I use them.
  2. (*steve*)

    Need help in designing a simple device

    This should do it. I would use 1% resistors for R3, R4, R8, and R9. 21k is an unusual value. You can make it out of two 10k resistors and a 1k resistor. R2 and R6 should be trimpots (i.e. screwdriver adjustable, not with a shaft for a knob). U1 to U4 can probably be a quad op-amp. Note...
  3. (*steve*)

    What's so special about mini-MELF 1N914s?

    OK, a surface mount 1N914 is a pretty cheap "jelly-bean" component, right? Well, check out the price in the DO213-AA package! Also here. Why so expensive?
  4. (*steve*)

    Light therapy device

    Then we have an interesting task. Have you ever done surface mount soldering?
  5. (*steve*)

    What is ohms law (was Ic=C x dv/dt)

    We're not in Kansas any more. No need to limit yourself to the original request. :-)
  6. (*steve*)

    Analog Voltage recognition by Microcontroller ADC

    Depending on the value of the R and C in the input low pass filter, it may take some time for the voltage to settle at the final value, or it may have some ripple left on it. Are you looking for a specific value from the adc, or a value in a small range? What value are you expecting and what...
  7. (*steve*)

    Capacitor type comparison

    Without units those numbers are useless. 0.030 something's is way less than 12 something's, but more than 12 mili-somethings.
  8. (*steve*)

    Need help in designing a simple device

    I'll see if I can draw up the circuit for you with suitable value resistors. I can't do it on my phone so it will have to wait a while :-)
  9. (*steve*)

    Need help in designing a simple device

    You don't need pots, you need op-amps and fixed value resistors. You need gain, not just loss.
  10. (*steve*)

    Plotter Cutter Help

    Aaagh! Perhaps some better photos are in order. (Please see here).
  11. (*steve*)

    Plotter Cutter Help

    I don't suppose you have access to an oscilloscope? I suspect there is something that is reducing the duty cycle of the regulator to almost zero. With the photos you've shown, I can't figure out how the optocoupler gets turned on only when the voltage hits the required value. Typically...
  12. (*steve*)

    Which microcontroller best fits my needs?

    With Arduino (or an atmega environment) you can leverage heaps of code that's available freely. With cortex, I have no idea. I expect there's a development environment (no idea if it's free) and I have no idea what libraries are available. Oh, I didn't answer the previous question about...
  13. (*steve*)

    Plotter Cutter Help

    I'm not sure I understood what you did. It sounds like (If you did what I asked) that placing a 1k resistor between either output and ground did little to the output voltage. The next thing to do would be to carefully measure the resistance across the output of the optocoupler. This is the...
  14. (*steve*)

    Which microcontroller best fits my needs?

    Yeah, but if you feel the need you can overwrite it with your own code. Those extras shouldn't affect the performance. If you really want to , you can just use the same chip and leave off all the extra stuff. Modularity. Redundancy. Simplicity. Yeah, but uing the arduino means that all...
  15. (*steve*)

    What is ohms law (was Ic=C x dv/dt)

    Most materials are, or can be considered to be ohmic at a single point.
  16. (*steve*)

    Which microcontroller best fits my needs?

    Your requirements suggest you're a beginner with microcontrollers/programming. In that case, I'd go for an Arduino Mega 2560. Personally, I wouldn't put all my eggs in one basket. I would build a stack of independent modules based on simpler microcontrollers and interface them (via wireless...
  17. (*steve*)

    Time Counter From Manual Pulses

    Google "digital clock schematic". These days you'd probably use a microcontroller. If I had to put something together like this in an afternoon, I'd probably grab an arduino.
  18. (*steve*)

    What is ohms law (was Ic=C x dv/dt)

    My point exactly.
  19. (*steve*)

    What is ohms law (was Ic=C x dv/dt)

    And area = 1/2 base x height only works for a triangle with straight edges. For example A = 2.pi.r/2 * r Because a circle has straight edges when you look at a sufficiently small segment.
  20. (*steve*)

    R/2R resistor ladder

    It is the voltage present on A, B, and/or C when they are in the "1" state.
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