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  1. BobK

    DC-DC variable voltage and current lab power supply

    A constant current supply attempts to supply the set current into the load by adjusting the voltage up or down. Of course there is a max voltage it can supply and it will fail to supply the set current if it requires more voltage than the max. A current limited supply normally is attempting...
  2. BobK

    LED FORWARD CURRENT & VOLTAGE

    If you don't know any of the forward voltage, current or power, I see no way to determine these parameters. If you know any one of them, you can find the other two. Edited to add: The basic problem is that the LED will operate at above the rated power form some period of time, then fail...
  3. BobK

    555 Timer Discharge Pin 7 Question..

    The discharge transistor is on when the output is low. You can see this in the block diagram in the datasheet. The base of the discharge transistor is connected to an inverter which is the output. So when the inverter input is high the discharge transistor is on and the output is low. Bob
  4. BobK

    DC-DC variable voltage and current lab power supply

    Well, there is no provision for it in the chip, but I can think of two ways to do it. 1. Compare the voltage across the current limit resistor to a reference and when it is at the limit light the LED. 2. Compare the voltage on pin 4, the voltage sense, and if it is below Vref of the...
  5. BobK

    Best type(s) of capacitor

    I am curious, what is the problem with multi-layer ceramics? Do they have a resonance or something? As I undertand they are quite good for low ESR applications. Bob
  6. BobK

    spreading out the PWM on a PIC16F627a

    Yes, given a fast enough micro. You will need to do say 100 levels at 100 updates per second. This is 10000 interrupts per second. The newest low-end 8-bit PICS run at 8 MIPs, so that gives you 800 instruction times to update 6 outputs. A piece of cake. Bob
  7. BobK

    spreading out the PWM on a PIC16F627a

    Adding hardware when the PIC can do it seems, well, inefficient. A good software PWM can easily handle fading of 6 LEDs. Bob
  8. BobK

    invention/adapter

    Yep, so it cost less than a dollar to replace the outlet if you can do it yourself, and a couple of beers if you can't but have a friend who can. bob
  9. BobK

    invention/adapter

    If you go overboard with features, the adapter is going to cost much more than replacing the outlet. Bob
  10. BobK

    IR Receiver Output Problem

    Okay, I didn't see the post about the LED. That is certainly the problem. Bob
  11. BobK

    Why does speaker on output click twice on 555 timer output?

    1 minute too late. Bob
  12. BobK

    Why does speaker on output click twice on 555 timer output?

    When the output goes high, the speaker cone is pushed out -- click. When the output then goes low, the speaker cone returns -- click. Bob
  13. BobK

    Increasing motor's RPM + Torque with stronger magnetic fields?

    The executive summary: Less magnetic field means less back EMF, means more current drawn at the same voltage means more power drawn means motor spins faster. Bob
  14. BobK

    IR Receiver Output Problem

    What else is connected to the PIC pin? If nothing else, then your PIC pin is an output which is overriding the output of the sensor. bob
  15. BobK

    How to generate AC frequency from DC waveform

    A bridged audio amp is the basically an H-bridge that is driven linearly. It is used to get twice the voltage and hence 4 times the power into a speaker. Bob
  16. BobK

    Increasing motor's RPM + Torque with stronger magnetic fields?

    Did you measure the current being drawn? Voltage is not the same as power. Voltage times current = power. Bob
  17. BobK

    IR Receiver Output Problem

    If you are reading 1.6V at the output with no signal something is wrong. What do your read when the PIC is not connected? Bob
  18. BobK

    How to generate AC frequency from DC waveform

    The circuit is called an H-bridge. It allows you to get 24V p-p from a single 12V supply. Essentially you have 4 transistors in two push-pull arrangels. Two switch from 0 to 12 and the other two switch from 12 to 0 and the same time. So the output is taken between them, at the junctions and...
  19. BobK

    Digital time zone clock/temprature sensor project

    Except for the number of outputs. One PIC + port expanders or shift registers, yes. Bob
  20. BobK

    IR Receiver Output Problem

    Connecting the output of the receiver to an input of the PIC should not change the output voltage. Are you sure the PIC pin is not set as an output? bob
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