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  1. BobK

    Function generator and impedance

    Easy. Put an amplifier between the output of the signal generator and the speaker. It is not just a question of impedance mismatch, it is a question of how much power can be supplied. A typical function generator is not designed to drive a speaker. Bob
  2. BobK

    What is the best way to tun on and off a pic16f1847 using a microswitch?

    Have the PIC sleep and wake upon the button press. Then check that it is still pressed after the desire interval before powering up the rest of the circuit. If you arrange that nothing else is drawing current while in sleep mode, the current draw is miniscule. Bob
  3. BobK

    Small Circuit needed for New Product Design - Help!

    For surface mount parts, the matrix board is not going to do it. You either need to use the PDIP version (which is much larger) or have a PCB made. I recommended that part because the LCD driver will operate while the micro is in sleep mode, which really simplifies the programming and gives...
  4. BobK

    Simple relay circuit help

    Of course colors do look different on different monitors. Bob
  5. BobK

    Hobbyist Techniques for Reflow?

    Did you use a solder sucker or copper braid? It is very hard to remove parts with just a soldering iron. Bob
  6. BobK

    Motion sensor lighting with a difference

    Any chance you could use something that passes infrared but looks opaque to the eye because it blocks visible light? Sort of like the front of a TV remote, which looks black but actually passes IR. Bob
  7. BobK

    Simple relay circuit help

    Huh? I see two resistors with orange orange red and one with brown black orange. 3K3 and 10K as in your schematic. Bob
  8. BobK

    Urgent issue with encoder interrupts and PID control

    Great! Keeping interrupt routines short and sweet is really rule number 1 of real-time programming. Now you have learned it well. Can't help you with PID controllers, as I have not done any yet. I plan to do some robotics experimentation myself on my sabbatical later this year, so I will be...
  9. BobK

    UV Light box design

    My theory is you start simple and only get more complex as you need it. It sounds like you are trying to build the ultimate device without ever having tried simpler and less costly methods. Bob
  10. BobK

    Urgent issue with encoder interrupts and PID control

    If I understand you correctly, you are calling your PID controller code from an interrupt handler. That is not the way to do it because interrupts will be disabled too long. Your idea to set a flag in the interrupt handler that is then checked in the main loop is the right idea. Interrupt...
  11. BobK

    Urgent issue with encoder interrupts and PID control

    If you are disabling interrupts in your code, the time that they are disabled must be < the time between interrupts or you are going to miss some. Can you rewrite to code to avoid disabling interrupts or at least keep the time minimal? If the problem is missing interrupts while another...
  12. BobK

    UV Light box design

    Considering that I got excellent results with a 15W daylight fluorescent mounted 5in above the board covered with an acrylic sheet, I think you are overthinking it. Take a look: https://www.electronicspoint.com/threads/photo-resist-pcb-help.268585/#post-1609340 Bob
  13. BobK

    Need help with a radio project!

    If it has a bridge rectifier for the power input, you can place DC of about 1.4x the AC voltage. And you can put the pos and neg either way! Bob
  14. BobK

    Hobbyist Techniques for Reflow?

    I have not tried reflow yet. I've soldered 0603 and SOT using paste and then just touching each side with tip of the iron. I've soldered 44 pin SSOP using drag method (tack two corners, then drag a blob of solder across all the pins on one side, making a mess, and clean up with desoldering...
  15. BobK

    Need help with a radio project!

    Kris already told you how mix the two channels. Simply place a resistor between each output and the single input. He suggested 3K3 which I would concur with. Bob
  16. BobK

    driving analog frequency through a digital component

    Analog and digital are not properties of a signal. They are two different means of encoding information into a signal. A signal might be a voltage, a current, a frequency, a phase difference, a duty cycle and probably others I cannot think of right now. Any of them can carry either analog or...
  17. BobK

    Small Circuit needed for New Product Design - Help!

    What kind of module? Like a text display? Bob
  18. BobK

    Measure time when ground connection is lost ?

    Your wristband, without any other connections to the body to ground, could only send current from one side of the wristband to the other. Bob
  19. BobK

    Small Circuit needed for New Product Design - Help!

    I just paged through the LCD driver section of PIC you found. What they go through the multiplex is mind boggling. You have to make sure that each pixel never sees more of 1 polarity than other and they go to great lengths to make this happen. Interesting reading. A periodic wake-up would...
  20. BobK

    Small Circuit needed for New Product Design - Help!

    Ah, there is a 28 pin PIC with LCD driver. When I looked, for some reason, I could only find a 100-pin one. So, with that new knowledge I would use the PIC16F1902. This would allow driving the LCD display while in sleep mode and waking only on button presses, which would make the battery life...
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