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  1. C

    Drilling pcbs

    I get double-sided PTH boards 100mm x 100mm, 800 holes, legend and HASL made for $2.50 each. I wouldn't waste my time drilling the first hole for $2.50. I used to make my own resistors, then I found I could buy them for 1 cent each. Gee . . . .I am so clever.
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    Need to find a way to do different functions basedon incoming voltage

    12v or 24v This circuit turns on a red LED when 12v is present or the green LED when 24v is present:
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    Combining multiple amplified outputs to feed one speaker only

    Put a 1u (non-polar) on each of the tone lines and connect them across the speaker.
  4. C

    Combining multiple amplified outputs to feed one speaker only

    I would connect all the 0v lines together and put the 10R and diode on the "active"or "signal" line.
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    why it become 20vdc after bridge rectifier while supplied 18vac

    The regulator is either connected around the wrong way or the "common"terminal is not connected to 0v or the regulator is damaged. The 12v regulator can deal with 15v to 25v.
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    Combining multiple amplified outputs to feed one speaker only

    You could try 10R in line with a diode from each of the tones and connect the speaker directly to the audio amp.
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    Microcontroller controlled by pushbutton for LED flashlight

    The counterfeit product is just as good/bad as the original. You will have just as much trouble getting the thing to work.
  8. C

    PIC 1.5V Output

    Rather than building the TaJ Mahal to deliver 1.5v with PWM, you need to specify how much current you need. Nothing can be answered without this specification.
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    4017 & 555 Police LED Lights Project (noob question)

    "Can you please be more specific on why the resistor layout is not wasting power?" The resistors perform two functions. They limit the current and form a "gating" function.
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    4017 & 555 Police LED Lights Project (noob question)

    "Both diagrams have a current limiting resistor before the transistor, and for each series sets of LEDs. So they do indeed have current limiting." I said the Siren Circuit.
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    4017 & 555 Police LED Lights Project (noob question)

    Here is the simplest circuit: http://www.talkingelectronics.com/projects/50%20-%20555%20Circuits/images/PoliceLights-2a.gif
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    4017 & 555 Police LED Lights Project (noob question)

    The siren circuit is a very bad design. It does not have any current limiting. "They are just wasting power compared to the diode solution. " This is incorrect.
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    Resistor identification

    If they printed values on resistors, EVERY MAN AND HIS DOG would be able repair electronic equipment. The values are in rings so the resistor can be placed at any angle in a circuit and the value is still able to be viewed.
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    Suggestions for building a PIC dev. board?

    "if you don't need as much current you can dial back the base resistor." I don't know what you mean. The transistor is only taking 1mA and the output of the chip can be used for other purposes or other loads. Any of the outputs can be converted to inputs at any time during the running of the...
  15. C

    Potentiometer characteristics

    "I got it from your website under 1-WATT LED - a very good design" You are getting mixed up with series and parallel connection. "The O.P. did not give any other information other than the LED has presumably a 30mA maximum." I have never heard of any 3mm and 5mm LEDs with a current rating of 30mA.
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    Suggestions for building a PIC dev. board?

    "whereas the PIClick's outputs are all tied to a transistor." The outputs are NOT all tied to a transistor. You can add anything to any of the outputs. In the development board above, you won't get much brightness out of the 7-segment displays without driving them via transistors. And even...
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    Suggestions for building a PIC dev. board?

    "The picklick seems to have been built solely for output." What do you mean????? The PIClick has 5 inputs and 8 outputs. If you haven't already realised, the PIClick project is a play-on-words to the STAMP where the Stamp cost $18.00 to $45.00 for less performance.
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    Potentiometer characteristics

    Firstly you say 3mA change in current will be hardly noticeable and then you talk about 10% tolerance resistors can be a problem. Where can you buy a 10% tolerance resistor ??? Yes, believe it or not, LEDs are designed for 17mA and say 50,000 hours. When at 20mA, the life drops to 20,000...
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    help me to design simple buzzer

    " I need 90 beeps per min, 1.5 Hz" What do you mean?
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    Potentiometer characteristics

    "I doubt their would be an perceivable difference in brightness " Can you rite in Emglish? "Remember that resistor tolerances can range quite a bit" When was the last time you bought a resistor??????? "each LED would receive about 27mA of power." Where did you learn your electronics from...
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