Search results

Search Forums New Posts
  1. Alec_t

    NPN transistor audio amp

    Googling "one transistor amplifier" will get you lots of circuits to look at.
  2. Alec_t

    Electric Fence Charger

    The continuity test function on a multi-meter performs a DC test. Capacitors are designed to block DC, so will appear to be open circuit.
  3. Alec_t

    What reason could be for a food processor's motor to run backwards?

    No wonder it runs backwards. Even the label is reversed :). Seriously though, the cracks in the plastic blade-holder suggest someone has at some point removed the blade assembly from the motor shaft and re-assmbled things arse-about-face. Given those cracks, the assembly could disintegrate. I'd...
  4. Alec_t

    Convert 12V to 3V Without affecting Total Resistance

    Many analogue inputs require a source impedance of less than 10k for accurate, reasonably fast A-to-D conversion. But a10k voltage divider across your 1k would drop the '12V' by around 10%, i.e too much. That points to you needing an op-amp to buffer the signal.
  5. Alec_t

    SUPPRESSOR?

    Sounds like a 3-capacitors-in-one-housing EMI suppressor as used in many domestic appliances which include a motor. The 25nF cap would be an X-type connected directly between the two supply rails. The two 5nF caps would be Y-type, connected in series, the series combo being connected between the...
  6. Alec_t

    Help with MOSFET motor control

    So do I. My understanding of the circuit intent is that taking Start high turns on Q3 fully so that Q1 can then PWM the motor under 555 control. Taking Start low turns off Q3 and turns on Q2 to provide motor braking (albeit pulsed by virtue of the 555).
  7. Alec_t

    Burnt drain resistors on switching regulator

    For those resistors to fry, the MOSFET above them would almost certainly have passed excess current and died too. The possible reasons for MOSFET failure include load impedance too low, high-frequency spurious oscillation, incorrect feedback to the control circuit driving the MOSFET, and failure...
  8. Alec_t

    DC 12-36V Lathe Press 555 Motor, Torque vs speed

    The rated output power of the motor is 75W, so you won't get >100W out of it (except, perhaps for very brief periods) without overheating it. Your supply will have to be rated to handle the motor's start-up/stall surge current, which could be several times the expected 3A or 5A. Would your 24V...
  9. Alec_t

    Op amp problem ua741

    :confused: The datasheet shows the minimum input range is ±11.5V when the supply is ±15V. That is not rail-to-rail input.
  10. Alec_t

    Or gate with shift register

    I'm sure they are :).
  11. Alec_t

    Or gate with shift register

    I'd use a length of wire or a PCB trace.
  12. Alec_t

    Replacing thermostat in a fog machine

    The link shows a family of thermostats. Which temperature rating does yours have?
  13. Alec_t

    Generator questions

    The output voltage and maximum current would be highly dependent on magnet strength, coil inductance/resistance/number of turns, coil core permeability, physical dimensions and spacing of all components. There is no simple way of calculating the output. Build your machine and run it. Take...
  14. Alec_t

    Op amp problem ua741

    The 741 doesn't like input voltages within a couple of Volts of its +ve or -ve rail. Check the datasheet.
  15. Alec_t

    Driving a piezo buzzer: resultant tone is noisy. Why?

    In the linked buzzer device the piezo element is mounted in what is effectively an echo chamber, so that will have a natural resonant frequency (which looks to be about 5khz in the 'scope trace). Edit: As per the post below, 3.6kHz is a better estimate. Bob has better eyes than me :).
  16. Alec_t

    falstad

    ..... but LTspice is for serious simulations and doesn't have the same animated user interface that Falstad has and which beginners seem to like (but probably get fed up with after a short time :) ).
  17. Alec_t

    Omnidirectional Ultrasonic transmitter

    How about something like these?
  18. Alec_t

    Omnidirectional Ultrasonic transmitter

    I think the nearest you'll get will be an array of small transmitters pointed in different directions.
  19. Alec_t

    Have seen many Youtube videos related to induction heaters but never for water?

    I agree with Kelly. Standard heating elements would be far more efficient than induction heaters.
  20. Alec_t

    Solar Immersion Controller - Noise Issues

    If the manufacturer reckons your ADSL filter will cure the problem, isn't that effectively admitting that the product is emitting undue RF interference? Such emission would be contrary to the EC Directive.
Top