Search results

  1. audioguru2

    Power Supply Meter Problem

    Hi Woody, Don't link the input to its own supply. Have you asked the meters' manufacturer what they recommend?
  2. audioguru2

    Electronic Stethoscope 2

    Hi Loveguru, Does the LED change slowly from red to green back and forth? Then you probably have 47uF for C3 and C4 instead of 47nF, so they are 1000 times too much capacitance. 47nF is also 0.047uF. Measure the DC output voltage of U1a and U1b, they should be very close (less than 20mV) to zero...
  3. audioguru2

    Voltage Reducer

    Hi Steven, Of course regulators reduce the voltage. The 78xx regulators need an input voltage at least 2V or 3V higher than their output, and can have a maximum input voltage of 35V.
  4. audioguru2

    Transformer VA ?

    Hi Zybitx, When you load the transformer, you will find out its power-handling capability when it burns-out or over-heats. If you know the size of the TV it was in, look at the power rating label on a similar TV. Or go to the electronic parts store and see the rating for a similar-size...
  5. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Kain, He, he. Yea, I dunno what was wrong with me too. ::) I was thinking of the 3A corrected version of this project that needs only a single 10,000uF cap. You don't need 50,000uF for only 5A, it would reduce the raw ripple to only about 0.4Vp-p. I think 20,000uF is fine. Your nice...
  6. audioguru2

    Frequency Detector

    Hi Art, Welcome to our forum, 1) What is making the frequencies? 2) How many frequencies do you want to detect? 3) Are the frequencies all the same amplitude, and the same each time they occur? 4) How quickly does each frequency repeat?
  7. audioguru2

    Transformer VA ?

    Hi Zybitx, Welcome to our forum. VA is the power that the transformer is rated to deliver to a load. Power is Volts times Amps. You show only five unusual voltages without any current (A). Usually a power transformer has only one output and its voltage is rated with a rated current or VA rating...
  8. audioguru2

    Convert 0-30V 3A PSU to 5A or more

    Hi Kain, Where on earth (or maybe not?) do you buy stuff? Where do you buy a big, powerful transformer for only $10.00? Here is Digikey's reasonable price for the IC and their high quality (105 degrees) 10000uF/63V cap is about $7.00:
  9. audioguru2

    Posting Instructions

    I am receiving instant messages from newbies asking about the very basics of how to post. I had the same problem when I joined our forum and still don't know all the details. Does anyone have detailed instructions including all the YABBC tags? Thanks ???
  10. audioguru2

    Voltage Reducer

    Hi Paul, Welcome to our forum. Use an LM7812 12V voltage regulator IC, 2 capacitors and a small heatsink (it wastes 3W while reducing the voltage). Search on Google (WWW Search button below) for its datasheet.
  11. audioguru2

    again, microphone input high school project

    Hi Zgnoh, At the bottom of this page is a link "WWW Search" to the Google search engine. You can enter part numbers, circuit names or anything. I entered LM3915 and it linked to this datasheet: http://www.national.com/ds/LM/LM3915.pdf You will see that it has 10 outputs arranged in steps of...
  12. audioguru2

    Power Supply Meter Problem

    Hi Woody, Your meters' displays are probably multiplexed and might be radiating RF interference to each other. Try small capacitors across their inputs and/or a grounded shield between them. Long ago there was a multiplexed display IC that had the rising and falling edges of the LED driver...
  13. audioguru2

    again, microphone input high school project

    Kevin, Ripple doesn't come from the input. It is the result of the cap discharging a bit into the load between charging pulses from the diode.
  14. audioguru2

    again, microphone input high school project

    Kevin, Without a load (but maybe your meter or 'scope) the cap won't be discharged by anything so won't have any ripple. Maybe your rectifier diode is too slow for your frequency. 1N400x diodes are very slow, try a fast 1N4148 diode.
  15. audioguru2

    Power Supply Meter Problem

    Hi Woody, You are correct. I checked the LED current for new LED digital meters and it is spec'd at 41mA, but they don't say how many segments are lighted. Therefore your little transformer is operating close to its limit. I have found that very small transformers are very inefficient, not...
  16. audioguru2

    again, microphone input high school project

    Kevin, yeah.
  17. audioguru2

    again, microphone input high school project

    Kevin, Your cap should have charged to the peak voltage of your triangle wave, or any other AC, minus a diode voltage drop. Since you say the DC voltage was low, then you also need a preamp as described in my very 1st reply to this topic. With a load resistance and capacitor value time constant...
  18. audioguru2

    Power Supply Meter Problem

    Hi Woody, You're overloading the little transformer with all the LEDs in your meters. If you have two 3-digit meters they have a total of up to 34 LEDs that could be lighted when displaying 1.88. Assuming a not very bright current of 10mA for each LED, their total current is 340mA! Plus current...
  19. audioguru2

    again, microphone input high school project

    Kevin, The charging time of the rectifier's filter cap depends on the cap's value and impedance of the source. If you use a 0.1uF filter cap, the milli-ohms output impedance of the preamp will charge it through the diode to the peak of the audio immediately. Then you could use a 1M load resistor...
  20. audioguru2

    again, microphone input high school project

    Hi Zgnoh, It would be cool to see your water fountain squirt by the various levels of music. With most pop music it would squirt to the beat of the music! 1) The LM3915 can have a switch to select a single output called dot mode when it lights LEDs, or bar mode when it lights all LEDs below the...
Top