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  1. duke37

    what do I have here?

    I have one somewhere that resonates at 100kHz. I compared it to Droitwich and could slip a cycle in more than 10sec.
  2. duke37

    Hight input impedance DC buffer ?

    The output impedance will only become asymmetrical when the transistor current has reduced to zero so will depend on signal amplitude and load.
  3. duke37

    Light dimmer

    Maybe some temperature effect in the diac or potentiometer.
  4. duke37

    24VAC Step-up Transformer

    By stepping up the voltage, you will step down the current by an equal factor. In fact, if the available current is not sufficient, the voltage will collapse.
  5. duke37

    Which FM Aerial Plug is this?

    I read somewhere that they also come with two different threads.
  6. duke37

    24VAC Step-up Transformer

    You can make anAC relay more sensitive by driving with DC obtained with a bridge rectifier. An AC relay driven via a diode will be more sensitive and even more so with a diode across the relay.
  7. duke37

    Electronic Circuit error

    You need to localise the fault. Remove Q1 and see if the voltage is pulled low. Connect a link to replace Q1 emitter/collector and look at the effect. If the voltage is pulled low, remove D1. If the voltage then stays up, check D1 for short or correct direction. I do not find it easy to check...
  8. duke37

    150 w converter dc 12v to ac 220v inverter boost

    I see GND- , there will be GND+ somewhere for the 12V DC in. Possibly the other side of the large electrolytic capacitor. The low voltage trace will need to pass over 10A so will be wide. There is another connection by the corner of the transformer but I cannot read the letters. Is that a...
  9. duke37

    Unable to get solenoid controlled by Arduino to work anymore

    Your schematic shows the output connected to the base of the transistor. This is wrong. The arduino shoud drive the base through th 1k resistor. The emitter should go to negative supply and the collector to the solenoid.
  10. duke37

    Simple moisture meter circuit?

    Just click on "a schematic for a DIY project"
  11. duke37

    Recommendation for bidirectional brushless DC motor torque on the cheap

    Accereration This is mass * rate of change of velocity. If accelerate in 1sec Acc = 1.25 m/s/s Force is mass * acc = 5 * 1.25 = 6.25N This is much less than the lifting force. If however you accelerate in 0.1sec then the forces are comparable.
  12. duke37

    Recommendation for bidirectional brushless DC motor torque on the cheap

    To lift 5kg (not KG) you need a force of 5G that is 5 * 9.81 = 50N roughly. The torque will be 50 * pulley radius. The power will be force * speed = 50 * 1.25 = 625W. This will be quite a beefy motor.
  13. duke37

    help! Unknown prong type!

    It looks to me to be bigger than two pin din, so check the size. What voltage does your wall supply? I assume that you want the snowman to run from a wallwart which provides the correct voltage at sufficient current. Get the polarity correct. It is not clear to me what the plug is connected to...
  14. duke37

    SERVO POSITIONING??

    It would be simpler to use a solenoid to yank the barrel back. return with a spring. Then all you need will be a pulse generator such as a 555 and a driver (mosfet) to drive the solenoid.
  15. duke37

    Looking to power a peltier with <9V

    I would try a 6V/12V battery charger of the old type. A 4A charger should be able to run more than 4A for 10sec. Why does the efficiency change with current level?
  16. duke37

    Speaker power (wattage) and consumption

    And keep the volume down below clipping level. When the amplier clips it produces high frequency harmonics which can damage the tweeter should one be present. Just treat the system with respect.
  17. duke37

    Speaker power (wattage) and consumption

    The speaker efficiency is very low. The output will be well less than 1W.
  18. duke37

    Resistors, Capacitors, Zener diodes... Why the funny values?

    A mere chicken:) You will have to run to catch me up. The trouble with old age is that you have to learn the same thing over and over again.
  19. duke37

    Blocking DC voltage on an AC circuit

    A DC component in the transformer secondary could push the core into saturation and allow the primary to pass very high currents. One way to get arround this is to put a capacitor in series with the secondary. If the offset is in the primary, then a selected diac in the control may help...
  20. duke37

    Resistors, Capacitors, Zener diodes... Why the funny values?

    An analogy of the odd values can be seen in the choice of frequency in the normal music scale. There are twelve notes in an octave - yes there are - and the difference in frequency between one note and the next is the twelfth root of two, about 6%. Multiply the frequency of a note by this...
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