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  1. audioguru2

    Want to use LED Dot Matrix Board

    Hi Masterlieous, You must multiplex the display by lighting each column one-at-a-time, one after the other at a high frequency so that your vision is fooled. It is fairly complicated so I'll let someone else tell you how they already did it.  ;D
  2. audioguru2

    Can I run two regulator circuits off one transformer secondary?

    Hi RDL, No Problem. If the regulators share the same ground, they can also share the rectifier and main filter cap. Just make sure that the transformer, rectifier and filter cap can provide the total current.
  3. audioguru2

    fm tranismiter

    Hi Sasi, I don't know where to buy oriental transistors in Canada. Maybe in Hongcouver.
  4. audioguru2

    laser idea

    Sorry, I looked at 20nm instead of 20um:
  5. audioguru2

    Re: Alun's low voltage alarm

    Hi Alun, The project isn't corrected yet and still calls its quad open-collector comparator an opamp.
  6. audioguru2

    radio transmitter

    Hi Sp, Welcome to our forum. We have been talking about FM transmitters. I designed one that goes much further than only 2m and sounds great. Its pic and schematic are in this post: http://www.electronics-lab.com/forum/index.php?topic=2814.new#new
  7. audioguru2

    fm tranismiter

    Hi Alun, You have an excellent idea to solve my overmodulation problem!  ;D Let the preamp transistor symmetrically clip at full modulation: 1) Its existing max 5Vp-p output is way too high since full modulation is only about 20mVp-p. Use a decoupled voltage divider to feed its collector. Maybe...
  8. audioguru2

    Spellcheck Error

    It hasn't been taught English yet.
  9. audioguru2

    Puggy Potty Alarm

    Hi CRE, Changing the gain of the opamp won't make much difference because it already does exactly what the output of its driving 555 is doing, but is inverted. Maybe your piezo is drawing more current than the CA3130 can deliver. Measure its AC output voltage, it should be the same as the 555...
  10. audioguru2

    Re: Alun's low voltage alarm

    Hi Alun, This topic got moved and only its best parts were deleted! Did you notice that your fix for the original project got hijacked?  :o Let's watch and see if the project's schematic is corrected with it. It is too bad that it uses an open collector comparator instead of an opamp so it can't...
  11. audioguru2

    laser idea

    Its frequency is near the high end of ultraviolet waves and getting pretty close to X-rays.
  12. audioguru2

    fm tranismiter

    Thanks Trigger, I learnt that keeping wires very short in VHF circuits is very important.  ;D
  13. audioguru2

    PWM

    You can PWM the brightness of a lamp by audio loudness if you rectfy and filter the audio and use the resulting changing voltage to replace the pot in Alun's circuit. 
  14. audioguru2

    fm tranismiter

    Thanks Dazza,  ;D Yours should also work fine. Thanks Alun,  ;D Over here, a very popular TL071 costs less than a lousy old 741 or LF351. A TL072 dual costs even less! I always buy at least 10 and get a nice discount. Some experts like quieter audio opamps that cost an arm and a leg. This...
  15. audioguru2

    fm tranismiter

    Hi Guys, Here is a pic of my FM transmitter circuit built on a copy of Veroboard. It is Mod4, but using the circuit board of Mod3, so a few of its parts are very close together and I have resistor R6 and little ceramic cap C2 underneath. I have a 680 ohm resistor at the lower left as a...
  16. audioguru2

    PWM

    Kevin, If your inputs are not at the same frequency, you can't vary the phase difference between them and therefore can't produce pulse-width-modulation. If it is for a lamp dimmer or DC motor speed controller, if the input frequencies aren't the same then the lamp will flicker and the motor...
  17. audioguru2

    Re: Alun's low voltage alarm

    Wait a minute, Alun. We're not finished discussing it yet!
  18. audioguru2

    s-video to vga

    Hi Ras, You are lucky your signal isn't High-Definition. Maybe you need only a video card with a TV tuner on it. I got a Personal Video Recorder that records TV on its hard drive. Its digital picture and sound are much, much better than a VHS tape recorder and it can record and playback 2 shows...
  19. audioguru2

    s-video to vga

    Hi Ras, The converter isn't simple. I searched Google (why don't you?) for S-video to VGA Converter Circuit, and got links to hundreds of circuits. This is the 1st one:
  20. audioguru2

    Want to use LED Dot Matrix Board

    Hi Nan, If you can't find the datasheet for your LED matrix board, it would take you only a few minutes to make your own chart of its polarity and  how its pins connect to its rows and columns. Simply use a 4.5V battery (to avoid the 5V max reverse voltage rating of LEDs) in series with a 470...
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