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  1. BobK

    Is it possible to make Capacitive touch operated tone generation with a microcontroller?

    1) yes. 2) yes, if you only need a square wave, any micro could do it. If you need to produce another waveform, you might need a more capable one. 3) You would want a micro with 6 capacitive touch inputs and at least 1 output, A PIC 16F1705 seems to fit the bill. It is a 14 pin chip with 8...
  2. BobK

    simple circuit drawing software

    ExpressPCB is another free program that I would recommend. I use it for my DIY PCBs. I find its schematic capture and PCB layout to be very easy to use and capable enough for most of my work. The best thing about it is the ease with which you can add new components. Bob
  3. BobK

    PWM solenoid use

    I thought it was Fix Or Repair Daily. Bob
  4. BobK

    AC circuit (120v single phase) smooth to a10 sec. average voltage sine wave

    As I understand it, he wants to analyze the waveform over many cycles, then produce a waveform that, at each point in the cycle, gives the average voltage at that point in the cycles analyzed. Bob
  5. BobK

    Taming an unstable power rail

    I would add 100nF caps close to power and ground of each of the ICs. 10uF caps will not serve the same function because of higher internal resistance and inductance. It is too bad you did not start out with a star configuration for the power. Next time you probably will (I learned my lesson...
  6. BobK

    AC circuit (120v single phase) smooth to a10 sec. average voltage sine wave

    I understand what you are trying to do, even if no one else does. But what do you want to do with this smoothed sine wave? Are you going to power something with it, or is it just a low current signal that you want? Bob
  7. BobK

    When should you buffer a signal?

    It is not the impedance that matters, it is the voltage across the divider. The buffer ensures that the input impedance of the next stage does not effect those voltages. Bob
  8. BobK

    Taming an unstable power rail

    Hi, and welcome to the forum! Here are things that come to mind. Do you have the recommended capacitor(s) at the input and output of the 5V regulator? Do you have decoupling capacitors at all of the ICs? You say the power plane is in sections. Are there multiple sections connect via traces...
  9. BobK

    PNP transistor in CLass B push pull amplifier

    My circuit is actually class AB. The transistors are both on in idle mode passing about 2mA of current. If you did not do this, the sine wave would have an ugly jag in it around the zero point. And the two diodes make up for the base-emitter voltage drop in the two output transistors so that...
  10. BobK

    what wattage value would I use for the resistors in this schematic

    If that was meant to be a hit a Colin, it doesn't work out that way. 4.5-0.6 = 3.9 3.9 ^2 / 100 = 0.15 W, so 1/4 W is fine. Bob
  11. BobK

    PNP transistor in CLass B push pull amplifier

    That is a classic push-pull output stage, though, as noted by others, a capacitor is needed in the output if it is to be powered from a single supply. Here is an actual low-power (1/4W into 8 Ohms) amp that I have built: The Red trace is the output. The green trace is the emitter current in...
  12. BobK

    PWM to 0-10v

    Where are you getting the 0.8V reference for the - input? The voltage on the - pin is not 0.8V but is 0.8V * G / (G+1), so, what Hop suggested has to be modified to put that voltage, not 0.8V on the + pin. And this can be done with a voltage divider. Since you gain (G) is 2.7, you would...
  13. BobK

    Capacitors

    The newer solar lights have Li ion batteries and work much better than the old NiCad ones. Back to the original problem. Energy harvesting will be most efficient if the right sized battery is used. The only reason I can think of for using a large capacitor at all is if you can either get away...
  14. BobK

    Capacitors

    The capacitor and battery are fully specified in post number 22. Do you really think it makes sense to harvest energy into a capacitor with a battery backup that has 2000 times the energy of the capacitor? If it takes a day to harvest the energy into the capacitor, you will charge the battery...
  15. BobK

    Voltage control

    Wow, a twofor! Yes, that thread should tell you what you need to convert from one range to another. Bob
  16. BobK

    Capacitors

    My point is that the battery holds nearly 2000 times the energy of the capacitor. Under what scenario would this make sense? The battery would likely self discharge at a rate higher than you could cycle in charge from the capacitor. Bob
  17. BobK

    PWM to 0-10v

    No. It is giving 42mV or 0.042V, which is probably as low as the op amp can go on output. If you want to get all the way to zero, you will need to use dual supplies, which will make 0 part of the valid output range. Edit: But effectively 4mV is probably good enough. Bob
  18. BobK

    How to control AC current flowing through a transistor with a Arduino Microcontroller?

    An optical coupled triac is a good option. Bob
  19. BobK

    Capacitors

    What is the point of trying to transfer energy from a capacitor that holds 1/1900 of the energy of the battery to the battery? Bob
  20. BobK

    turn on/off a heat lamp, automatic.

    Yes, it exists, It is called a thermostat. Bob
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