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  1. BobK

    transistor switching question

    Do you realize why the original circuit did not work? If not, and for the benefit of anyone who does not, here is the explanation. The PNP transistor will be turned on by a voltage lower than that on the emitter. Since the emitter is at 12V, either 0V or 5V applied to the 1K base resistor...
  2. BobK

    Microcontroller controlled by pushbutton for LED flashlight

    It's not counterfeit if it is open source. Bob
  3. BobK

    Microcontroller controlled by pushbutton for LED flashlight

    On the other hand, it might actually work. The design is open-sourced, so it is likely to be an exact copy. Bob
  4. BobK

    Microcontroller controlled by pushbutton for LED flashlight

    Any socket solution is likely to be too large for your 14mm diameter board. The kind of pins for making temporary connects that Kris referred to are called spring-loaded contacts...
  5. BobK

    need to make a function generator

    What you need is Direct Digital Synthesis (DDS) chip instead of the MAX038. Google it. These can produce an arbitrary waveform at any frequency (up to a max of course) all controlled digitally. Bob
  6. BobK

    Stage Line 500W amp repair project

    If you look on the schematic, 45V is before the fuses, 45VL and 45VR are after separate fuses for the left and right channel. There should be negligible difference in actual voltages (assuming the fuses are intact). Bob
  7. BobK

    Using ohms law to calculate how many devices can be used with power supply

    A constant current supply provides exactly the voltage required to make the required current flow. If you measure the voltage across your red LEDs you will find that it is somewhere between 6 and 8V even though you are putting 12V into the driver. Now, as I stated before, the max number of...
  8. BobK

    Help: how to wire a potentiometer ?

    When using only 2 terminals from the POT, it does not matter which is connected to which point in the circuit. Just like it does not matter which lead from a resistor is connected to which point in the circuit. Bob
  9. BobK

    Help ID "Philips Remote alarm"

    PPM makes it sound like some kind of gas (CO for example) alarm. Bob
  10. BobK

    Stage Line 500W amp repair project

    Yep, blue, gray black brown is 6.8K You want red violet black red for 27K Bob
  11. BobK

    Flickering light (LED) circuit

    Alright, you just need to pass a little more current when the bulb is off to make the controller happy. Sounds good. Bob
  12. BobK

    2 pole low frequency shelving filter design

    Thanks for explaining that Adam. The capacitor blocks DC to the inverting input while allowing AC signals to operate normally. The capacitor is chosen to be a small impedance compared to the resistor it is in series with at the lowest frequency of concern. With a 10uF cap, the cutoff...
  13. BobK

    Flickering light (LED) circuit

    They were talking about WS467, same as one of them that you are using. When they say it steals power from the light, I assume they mean it is installed in a switch box with no neutral wire, which means the power to it comes through the light. I can see why this might not work with an LED...
  14. BobK

    2 pole low frequency shelving filter design

    Here: The output is centered on 1.6V. You will need capacitors on input and output to block the DC bias. Edit: You can reduce the 100u to 10u. Bob
  15. BobK

    Flickering light (LED) circuit

    Here is a thread about it on an X10 forum: http://forums.x10.com/index.php?topic=25646.0 They say noise created by the LED bulbs might be the problem. Bob
  16. BobK

    Flickering light (LED) circuit

    Aha, finally a clue. X10 uses communication over the power lines. I suspect that the noise created by one dimmer is interfering with the other. Bob
  17. BobK

    making a big magnetic field

    Well, the problem with that is, if you actually achieved your goal, you would probably destroy the cell phones of bystanders. That would be illegal. Bob
  18. BobK

    Activate a relay when resistance is within a certain range

    How did you determine that pushing the button causes a 240K resistance when it is pushed? That sounds very unlikely to me. And what resistance is it when not pushed? Bob
  19. BobK

    Using ohms law to calculate how many devices can be used with power supply

    You cannot run a constant current supply off 12V when the forward voltage is 12V. The supply will need a volt or two more than 12V to maintain the correct current. Can you link to the constant current driver specs? It should specify a maximum output voltage when run by 12V in. And do you...
  20. BobK

    2 pole low frequency shelving filter design

    That is because you are not putting a bias voltage on the + pin with that circuit, you are putting a current into it. You need two resistors, configured as a voltage divider to set the bias. If you keep the 100K resistor, try a 47K resistor from the + input to ground. This will give you a bias...
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