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  1. audioguru2

    help about this supply

    Most regulated power supplies use a voltage reference like a zener diode. This project doesn't, so I don't think its output voltage would be stable. It would change with input voltage, output current and temperature.
  2. audioguru2

    Help: Purchasing a Digital Multimeter and Soldering Iron

    At the 1st job I had, I found a Weller temperature-controlled WTCP iron in the garbage. I bought a new switch and tip for it and have used it with an old transformer I had for more than 40 years. I would never use a soldering iron without temperature control. A while ago, I bought an expensive...
  3. audioguru2

    500W_inveter

    Hi Ren, A metallized plastic film capacitor could also be called a mylar capacitor. Over on your side of the pond they are called "green-caps". The 0.1uF/5% capacitor would be marked "104J" if it is a green-cap. I've also seen reddish-brown ones. ;D
  4. audioguru2

    pbx/pabx project sites

    Hi Nolram, I installed, programmed and fixed pbx and key telephone systems. The very old ones used stepper switches and were simple. The last key systems I worked on in the '80's used a processor in each phone, on each card then an overall processor. Customers' offices were used as beta test...
  5. audioguru2

    Please tell me the alternatives of these

    Hi Shaiq, The IR receiver seems to have its IR diodes forward-biased and conducting all the time. They are shown upside-down! All IR communication circuits I've seen have the IR diode reverse-biased like this one:
  6. audioguru2

    Capacitor circuit design...

    Too dangerous! Go to a place where they print photos and ask for a disposable camera. Remove its flash-tube. Switch the coil across its capacitor after it has charged. It has a few hundred volts but isn't as dangerous.
  7. audioguru2

    Infrared Transmission

    Hi Ante, Thanks. I was near 5000 and I tried to cheat a little. I corrected spelling in some old posts hoping that each revision would be counted. Nope. Why are there so many lousy designs on the web? ??? There are too many for us to fix. Many use old obsolete parts. Maybe the circuits on the...
  8. audioguru2

    Infrared Transmission

    Hi Ryan, Welcome to our forum. ;D The transistors in the transmitter don't have bias current so their output will be zero until a certain input level is reached. The result with enough input level is extreme distortion. The receiver applies a fairly high current through your headphones which...
  9. audioguru2

    Laser Communication

    It is drawn looking like an LED. A Laser pointer uses a 2.2V Laser diode with a resistance of about 38 ohms. The resistance of the button cells is about 24 ohms. Therefore the total resistance of 62 ohms limits the current from the 3V battery to 13mA. My pic shows the spec's of a typical laser...
  10. audioguru2

    capcitive touch sensor

    Hi Ksp, Transistors connected as a darlington are current amplifiers. Each transistor has a current gain of 100-150, so Q3 drives the 52mA relay coil and Q2's current is only 350uA. Q1 supplies only 60uA to R4 and next to nothing to Q2.The sensor supplies only 3uA. The darlington connection also...
  11. audioguru2

    Input signal for LM3915. need help.

    You have the power supply pins connected correctly. Add a supply bypass capacitor. The same power supply can be used by all ICs or use an MC33172 dual opamp or MC33174 quad opamp. They have different pins. The MC3317x series operate from a supply voltage from 3V to 44V. Your circuit doesn't have...
  12. audioguru2

    Mystery voltage on input pins of 7408N (AND)

    You decided to use old fashioned TTL with its high input current requirement. I told you what to do: Add a 270 ohm resistor from each input to ground. Your +5V input signals must be able to supply a total of 74mA to the resistors.
  13. audioguru2

    ir sender.

    The relay going off appies a current to an IR LED. An IR LED can transmit IR to an IR receiver circuit if they can "see" each other, if the IR LED has enough current, if the IR receiver is sensitive enough and if there isn't other IR interference from sunlight or incandescent lights. The only...
  14. audioguru2

    Laser Communication

    Hi Shaiq, Your receiver circuit is nice and should work well. It uses negative feedback around its transistors to cancel differences between transistors. Your transmitter won't work with a condenser mic, it must be an electret mic. Many people confuse the two. The transmitter will kiss the...
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    Hi Gruber, The current-setting pot in this project has a tolerance of 20% and the values of the resistors were chosen so it provides 3A if the pot's resistance is 20% high. If your pot's resistance is 20% low then with it set to max, the project will try to produce 4.2A. Such a high current will...
  16. audioguru2

    Variable DC Power Supply

    It looks like older silicon transistors have different Veb breakdown voltages than newer ones. Looking at the only 3V rating of an MPSH11, I saw the 4.5V rating of some old 2N2369 transistors I still have. As for reliability, I was taught that when an emitter-base junction avalanches, hot spots...
  17. audioguru2

    "Safe" 5000 V

    A piezo lighter.
  18. audioguru2

    Flyback driver experiments

    I've seen small flouro bulbs for sale as replacements (I guess they burn out too) but I haven't seen a torch that uses them. I cut apart a dead compact fluorescent globe. They have a lot of nice electronic parts in there. HV power Mosfets and capacitors, tiny transformers and coils. Their power...
  19. audioguru2

    "Safe" 5000 V

    Half of 3 million volts is 1.5 million volts, isn't it? It isn't exaggerated. There is a link on another post to a 1 million volts DC thingy that produces arcs Four Feet Long! It uses four TV flyback transformers in parallel to power its voltage multipliers. I don't think anyone wants to be...
  20. audioguru2

    capcitive touch sensor

    The Capacitive Sensor project explains very well how it works: "Q1, Q2 & Q3 form a high impedance super-Darlington that drives the relay, amplifying the 50Hz alternate mains-supply frequency induced in the sensor by the human body. Note: For proper operation, circuit ground must be...
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