Search results

Search Forums New Posts
  1. duke37

    Exhaust fan for soldering build

    Magnetic materials can change shape when magnetised (magnetostriction) so transformers will hum. If the core consists of metal laminations, they can tap together and be quite loud. Should not affect the operation.
  2. duke37

    555 output to transformer failure

    How do you connect three cells in series and one in parallel?
  3. duke37

    Dodgy Chinese flip flop...or my circuit?

    You could use a cheap (2N2222) transistor with a base resistor (1k) to drive the relay. That would protect the circuit whatever is being driven.
  4. duke37

    Need help finding a weight sensing on/off switch? Like in lawn mowers.

    Fit a microswitch under the seat with a rod to activate it through a hole in the seat.
  5. duke37

    Transistor LED circuit_LED not blinking

    9V is a bit much since it can reverse bias the bases too much. Use a 6V supply or put a diode in series with the base
  6. duke37

    What type of switch is this and how does it work?

    In the UK we have PAT testing. All exposed metal parts must be connected to the earth wire and capable of carrying enough current to blow the fuse which should be as low a value as possible. It should be fed with an earth leakage breaker in circuit. You should test that there is no connection...
  7. duke37

    Dodgy Chinese flip flop...or my circuit?

    To protect your last circuit, run it with a small bulb in series with the supply. When all looks well, take the bulb out. Try it with a 330Ω resistor instead of a relay with no led. Try the led directly from the 14V to check that works correctly. Add the led if it is OK.
  8. duke37

    What type of switch is this and how does it work?

    Is that another coil at the top of the picture? If so,I agree with Bob. There does not seem to be any moving armature for a relay. The wire is fairly thick and it should be possible to rewind if necessary.With a shorted turn the fan will still work with an increased speed.
  9. duke37

    Electric Guitar Ampenstein

    Do not bypass fuses, they fail for a reason. Do you want a fire or a fatality if the electricity is going the wrong way? You can use a magnetron to blind yourself and others. For bending wood, use steam.
  10. duke37

    Understand VCO

    I got the text but not the circuit. The description seems to have been done quite well.
  11. duke37

    Dodgy Chinese flip flop...or my circuit?

    As I see it, the flip flop produces a switched voltage at a maximum current of 1500mA. I do not know where 1500mAh comes into it. The led should have a controlled current of 15mA. Putting 14V across it will kill it, possibly making a short across the output and so killing the flip flop. The...
  12. duke37

    555 output to transformer failure

    You will need a square wave from the 555, i.e. equal low and high times. I do not think that the circuit as shown will do this. What frequency are you generating, 90kHz? You could wind your own 1:40 transformer or use a buck convertor which can put much more voltage input than 9V, Limited by...
  13. duke37

    555 IC not amplifying enough

    I would do it if I were not shattered.:D
  14. duke37

    Transistors Query!

    A transistor will not generate current, you need a dynamo or alternator:). The current gain of transistors is variable over a wide range. You should not use a circuit which depends on it. To drop 9V to 5V, use a 7805 regulator which can manage up to 1A and may need a heat sink. Do not forget...
  15. duke37

    Need someone to check my circuit

    The power required to maintain a certain temperature will depend on the heat loss and not the volume of the bath. The time to reach the temperature required will depend on the mass which is heated. PID will not be needed if you have a time constant of a few minutes. Thermally insulate the...
  16. duke37

    Ultra Bright LED Dimmer with a sliding potentiometer

    The potentiometer will control the on/off ratio of the 555. It will NOT have the led current going through it. The resistor in the output which has been mentioned is to limit the peak current and can be made physically big enough to dissipate the required heat.
  17. duke37

    Transformer primary voltage exceed the rated voltage

    If the input voltage is high enough to saturate the core, then the input current is only limited by the wire resistance and the transformer will soon be damaged or your house will burn down. Another case where core saturation could be a problem is using a 60Hz transformer on 50Hz. Normally...
  18. duke37

    555 IC not amplifying enough

    A square wave has a little more fundamental than a sine wave of the same peak amplitude so should be more effective. It is also is easier to produce. The main problem would seem to be getting the right frequency. It may be possible to include the glass into a feedback oscillator but coupling...
  19. duke37

    Which chip used to optimize measuring many batteries.ject

    The 4066 has four switches which could be utilised. If the batteries are in series, the voltage could be very high. If the batteries are in parallel, there will be only one voltage to measure.
  20. duke37

    555 IC not amplifying enough

    The 555 will not be able to supply much current and a 741 much less. A simple transistor or fet as an amplifier can push the current up to 1A or more. You probably do not need much power to shatter the glass. Chose a glass (expensive) that will ring when stroked around the rim then set the...
Top