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  1. BobK

    Motor Unit operation

    A synchronous motor runs at the frequency of the AC power (or a divisor of it), hence the 3600 RPM whish is equivalent to 60Hz. You cannot slow this down except by changing the input frequency, so that is a no-go. Bob
  2. BobK

    Using Logic Systems

    I thought at one time that I might want to build a simple 4-bit micro out of transistors. But now I have upped the ante. My fun retirement project now is to design and build a 32-bit CPU using programmable logic, then develop the compiler and OS for it. I figure it might keep me busy for a...
  3. BobK

    Converting from AA to Li-Ion

    Show us the circuit. You can adjust the hysteresis of a schmitt trigger. Bob
  4. BobK

    Using Logic Systems

    I hear you. Fortunately I work in compilers, so I am still at the machine instruction level. But I could not get a job as an application programmer nowadays. You have to have 3 years experience with the XYZ framework running on top of the PQR platform communicating in the FGH protocol using...
  5. BobK

    Quick Op-amp Questions

    Okay then, you are probably better off with dual supplies. Bob
  6. BobK

    Quick Op-amp Questions

    What are you trying to do? I have often used opamps with only a resistor divider to make a 1/2 V reference. The power pins are connected to V+ and ground. The only problem with this configuration is that you cannot output ground (or V+). If the output can stay near the mid voltage range...
  7. BobK

    Digital Pot setup

    Your code is correct. The input to the controller is a CMOS and TTL compatible input which means it should have either a high or low signal connected to it. Low makes it run, high makes it stop. The bar ___ over the RUN means that it is active low, i.e. the function is on if the signal is...
  8. BobK

    PWM controller interfacing help needed

    Harald, Isn't your circuit providing a control voltage in the wrong direction? Your circuit may shift the level and the gain, but it is still providing a higher control voltage for a higher pressure, and (I presume) the higher control voltage raises the pressure. Isn't an inverting...
  9. BobK

    Digital Pot setup

    Setting the pin to low means that it is at ground. If the other end of the LED is connected (through a resistor hopefully) to V+, then it will turn on when the pin is low. You can also wire it the other way around, put the other end of the LED through a resistor to ground. Then the LED will...
  10. BobK

    How to connect POT and how this regiulator based charger behaves?

    This circuit is designed to limit the current to about 700ma. If you set the output to 5V then put a load resistor of 5R, which would normally draw 1A, the voltage will drop. Is this consistent with what you are seeing? Choose a load resistor of 10R, which would pull only 500 ma and see if...
  11. BobK

    Digital Pot setup

    No, you don't control an LED by voltage. The way they are typically controlled is by turning them on and off rapidly and varying the ON time. This is called PWM (Pulse Width Modulation). There should be info on using PWM in your PICAXE documentation. Bob
  12. BobK

    Running small relays... Voltage drop.

    How much is the coil supposed to draw, and what is the power supply rated at? Bob
  13. BobK

    Digital Pot setup

    Are you trying to run an LED off the DAC? That would not work. The way you control a LED to vary it's output is with PWM, another feature of the chip. Bob
  14. BobK

    How to connect POT and how this regiulator based charger behaves?

    It simulates fine for me in LTSPICE I can adust the voltage to anything I want and the current limit works. Sounds to me like you pot is bad, but you said it increased linearly when you measured it. Bob
  15. BobK

    Digital Pot setup

    The chip can provide enough current (up to 25ma) to drive an LED. Just be sure to use a resistor in series. Bob
  16. BobK

    Signs of Chinese progress

    Yes, my comment was intended as tongue in cheek. Bob
  17. BobK

    Signs of Chinese progress

    An actual fortune that I got in a cookie at a Chinese restaurant.
  18. BobK

    How to connect POT and how this regiulator based charger behaves?

    Is the wiper of the pot also connected to the negative of the battery and to the 1 Ohm resistor? Bob
  19. BobK

    IC with Interrupts and SPI/I2C

    This might help: http://www.microchip.com/productselector/MCUProductSelector.html Unfortunately interrupt pins is not a listed attribute. Most new PICs have IOC on many pins, why is IOC not good enough? It is more flexible than an interrupt in. Bob
  20. BobK

    A Digital Counter

    Fish debouncing! Bob
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