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  1. audioguru2

    Correct hall effect switch usage

    Hi Ryan, The datasheet for your hall-effect sensor shows that it has an open-collector transistor on its output. That transistor does nothing without a collector resistor to the positive supply. Even if you added a collector resistor, your circuit needs a high input like is provided by the...
  2. audioguru2

    Help: Circuit Design 4in NOR Gate

    Hi MP, I think you mean, "base-emitter" resistor. Its puny 7uA maximum current would be over-ridden by the gate driving current that is up to 161 times more. ;D
  3. audioguru2

    Transformer ratings?

    Hi Guys, Now if I could only get all the adwares and spywares that my new Internet Explorer6 is picking up to move like that. :o I found a site called "I am not a geek" that is helping me get rid of them.
  4. audioguru2

    Problems with headphones... static?

    Congratulations Steven, Hurray, you got the scrolling to work! ;D My 486 computer makes it jerk along, is it like that on newer computers? I'll try my son's Pentium4. Yeah, my old Sony walkman FM-stereo portable radio has bad static when I turn its dirty volume control. I'll have to clean it...
  5. audioguru2

    my retro pvr .. or personal video recorder

    Hi Mike, Welcome to our forum. I am renting (only 2 bucks a month) a Personal Video Recorder from my cable company. It is fantastic, it records 2 shows at the same time as I am watching another recording. It's great for time-shifting: Push "record" during a show, go get a beer or do something...
  6. audioguru2

    LM317 circuit doesn't supply enough current (only 20mA)???

    Hi Mike, What happens to your LM317's output voltage when you try to get more than 20mA from it? Does it just drop? Or do you get lots of hum and ripple?
  7. audioguru2

    Help: Circuit Design 4in NOR Gate

    Thanks MP, But I don't think an extra base resistor is necessary. The gate's output is either "active low" which turns-on the transistor, or "active high" which turns-off the transistor and keeps it off. A Cmos gate's output is at the supply voltage (or ground) without any load current.
  8. audioguru2

    Help: Circuit Design 4in NOR Gate

    Hi Simon, If you don't want to add doorswitches your circuit should work with a few changes (and if the relay coil's current is within the ratings of the transistor): 1) Add a diode across the relay coil to protect the transistor from the flyback voltage spike from the relay coil. 2) Replace...
  9. audioguru2

    high voltage photo flash capacitor charger

    Steven, the point of this discussion is that the relay's voltage is too low when driven by a 555 and 1N4148 that are straining so hard to cope with such a high current that they reduce the voltage to the relay. Your 12V relay's coil is probably getting less than 8.5V. Measure it to see. Maybe...
  10. audioguru2

    3V LED Chaser project

    Hi Guys, I just finished building another 3V LED Chaser, but this time I used Ultra-bright BLUE LEDs. Of course since they need 3.2V to light, I had to use a 6V battery of four AA alkaline cells. I used the same box, with 2 cells inside like before, and the other 2 cells top of its lid, secured...
  11. audioguru2

    high voltage photo flash capacitor charger

    Hi Steven, A voltage measurement across your relay coil will tell you what is happening with your circuit, but not what is happening with your lady.
  12. audioguru2

    high voltage photo flash capacitor charger

    Hi Steven, My wifey used to nag me, "Are you making another one?", "Your LEDs are blinding me" and "Get off the internet". But now that she has taken up knitting and going to cooking school, she doesn't bother me very much! Ah, now we get to know most of the details of your circuit, except the...
  13. audioguru2

    pseudo double-gang pots with transistors...

    Hi CRE, If you use a transistor (or FET) as a variable resistor the output will be terribly distorted because the signal voltage will also change the transistor's resistance. Why not use digital pots? They are ganged by simply tying their "up" and "down" control inputs together. They have...
  14. audioguru2

    high voltage photo flash capacitor charger

    Hi Steven, The 10uF electro in your 555 circuit is the timing cap that has nothing to do with the need for supply bypassing with the 2 additional caps. I don't know where you connected a 1N4004 since relays don't have inputs. Across the contacts? I can't remember the circuit of your HV driver...
  15. audioguru2

    Turn the lamp On & Off gradually...

    Hi Suraj, Getting the externally generated PWM frequency sync'd to the mains frequency would be difficult and would need more isolation. Forget having any mains isolation, nobody is going to touch the circuit. I know what you mean but the PWM isn't a triangle wave, it is produced by the output...
  16. audioguru2

    Reduce output Voltage of Power Supply

    Hi Ante, My bargain switchers are tiny little things that are rated at only 15W output. No air vents. I'm going to hack one apart to see where to drill a hole on the others for access to the voltage-adjust trimpot. I measured one and it has a 5.1V output without a load, and exactly 5.0V at 1.85A...
  17. audioguru2

    high voltage photo flash capacitor charger

    Hi Steven, You must measure the supply voltage to your timer circuit. If the battery voltage is low, it won't be able to supply the 400mA current spike from the 555's switching. The supply bypass caps are each connected from the 555's supply pin to ground (in parallel). The ceramic cap is for...
  18. audioguru2

    Transformer ratings?

    Hi Steven, 1) Click the moving "<M<" button that gives this: Bracket move bracket, bracket /move bracket. 2) Then type your words in between the center brackets. 3) You can add colour and size the same way, type your words in between the center brackets. G'day mate! 4) You can put a...
  19. audioguru2

    AM RECIEVER

    Hi Suraj, Thanks for the Navy link with its very good illustrations. But even those Navy folks got the theory wrong when they say, "The process of demodulation usually involves detecting the envelope of the AM signal. This may easily be accomplished by using a low-frequency filter (like a...
  20. audioguru2

    Transformer ratings?

    Hi Rhonn, Yeah, it's best to play it safe. If the mains voltage rose to 240VAC and the amp was lightly loaded or had no load but still had a high output signal, the output transistors would be swinging much more than their rated maximum voltage if you used a 220/25-0-25 transformer. You don't...
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