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  1. Alec_t

    Boost AC circuit

    How about use a solenoid valve which opens to release air when the well pump turns on, then closes when the well pump turns off?
  2. Alec_t

    Noob question regarding 555-DPDT relay-Motor

    As your motor is a low power one (since it runs from AA cells) you should be able to get away with reversing it 'instantly', but be aware that it is good practice normally to allow a motor to come to a stop before changing its direction of rotation.
  3. Alec_t

    Electrolysis (on as cheap as possible)

    For a given electrolyte conductivity, increasing the surface are of the electrodes will increase the current. Don't increase the voltage beyond 12V.
  4. Alec_t

    Water level indicator issues

    The top part of the circuit is missing. No wonder it doesn't work :).
  5. Alec_t

    EMF Detector

    Welcome to EP! 'EMF' = voltage, which you can detect with a multi-meter. Do you mean 'EMI' (Electro Magnetic Interference)?
  6. Alec_t

    Solar Car, Voltage determines Velocity

    Unless your wheels have a proper castor steering mechanism (e.g. Ackerman type) you will have in effect 'skid steering', such as is used by bulldozers. This will wear out your ty(/i)res in no time!
  7. Alec_t

    Epson EB460W projector- replaced auto iris now NO power

    Welcome to EP! Re-check that all connections are correct and sound. Any internal fuses?
  8. Alec_t

    Fitting resistor into lighting ring to stop flashing

    Be aware that a 100k resistor will be dissipating ~600mW and will get hot, so any adjacent materials and wire sleeving (heat-shrink seems unsuitable) should be non-combustible. The resistor should be well-spaced from other things to allow adequate ventilation. You should check with a qualified...
  9. Alec_t

    Beginner questions on wiring lights to speaker

    Google "color organ" for circuits you might find useful.
  10. Alec_t

    Wireless Power Transmission

    What steps have you planned to screen your kit electro-magnetically, so that it won't act as a powerful interference source to annoy the neighbours (and attract attention of the Authorities!) ?
  11. Alec_t

    Why are my LTSPICE results so different from the 1N4148 datasheet and real life?

    Did you mean to add links or attach something? Interesting though. At Vfwd=0.8V Vishay's datasheet shows a spread from 9mA to 20mA, NXP's datasheet shows ~40mA and Fairchild's shows 30mA. So on balance it looks like the Spice model is wrong.
  12. Alec_t

    Stop false alarms

    Welcome to EP! I can't help with the pulse counter, but I tamed my PIR sensor somewhat by putting a strip of reflective foil inside the lens part to restrict the angle of sight so that only bodies above a certain height would trigger the PIR.
  13. Alec_t

    Smoke machine heater replacement.

    Asuming the 800W heater is powered by the same voltage as the 600W one it will be drawing 33% more current. The thermal switch may or may not be stressed by that. Excess stress could result in a fried switch or worse ...... a lot more smoke than intended!
  14. Alec_t

    LM358 one opamp fails Please sugest what to do..

    If either the 12V or 400V is referenced to ground then your CT1 and CT2 inputs could be above your opamp positive supply voltage or below its ground rail. The opamp won't like that.
  15. Alec_t

    LED - troubleshooting why they do not work

    Welcome to EP! If a LED light has been working with a 38V supply then it probably consists of several LEDs in series. As you say, a common LED (white type) has a Vfwd of about 3V, so there could be 10 or more in a series string. If the LEDs are set in concrete outside the house the most likely...
  16. Alec_t

    Can hall effect sensor replace 50K linear potentiometer?

    I think you've got your Wiper and Dn connections transposed in the first schematic.
  17. Alec_t

    Circuit Diagram Help Needed

    Here's the text file. LTspice uses the .asc file extension, but you can open the file in any text processor, though you may have to change the extension to .txt. Goodness knows what Macspice will do with the file. Good luck. LTspice has a steep learning curve, but it's worth persevering. Its...
  18. Alec_t

    Circuit Diagram Help Needed

    Over 60 years :). I tried it without D1. The plot looks identical. Penfold's reference to voltage change with temperature applies to any semiconductor junction: the base-emitter junction of IC2a in this case.
  19. Alec_t

    Circuit Diagram Help Needed

    Yes. I don't think it does, unless you have a really large voltage coming from the keyboard input. The non-linear effect is produced in IC2a. The Penfold article explains. Here's a simulation of the circuit. The output voltage Vco is plotted for a keyboard input of 5V (yellow trace) and 12V...
  20. Alec_t

    Circuit Diagram Help Needed

    It would if it were forward-biased, but it is normally reverse-biased. The diode when reverse-biased plays no part in feedback. Feedback to the inverting input (pin 2 of the 741) is via Tr1. I haven't fully analysed the circuit.
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