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  1. duke37

    Help mitre saw blows house fuse

    The original plug is three pin. One of the pins is on the socket. It will be connected with three wires.
  2. duke37

    dc-cdi 12/220 issue

    pin 4,5,6,14 to 12vdc and pin 7,8,9,12 to ground ? I think that is right, you can check the data yourself. Check the frequency also.
  3. duke37

    Hitachi desk fan capacitor replacement

    I'm no expert here but the higher the voltage rating the better. A motor run capacitor is intended to run continuously, a motor start capacitor might object to continuous running. Size might be a problem with a high voltage capacitor.
  4. duke37

    dc-cdi 12/220 issue

    You can look up what mosfet is required when you know what it is needed to do. See #2. I have never used a microprocessor but to reduce interference put it in a metal box and filter input and output leads. Fast signals are particular problem. What is the processor for?
  5. duke37

    dc-cdi 12/220 issue

    I got my neighbour to scan and save the picture. Hope this is better.
  6. duke37

    dc-cdi 12/220 issue

    If you are using fets, the gates need to be pulled positive and negative. An emitter follower will only pull positive so a resistor, gate to ground, should be fitted to pull down, try 10k. I attach a picture of a suggestion for a simpler inverter and for two versions of the output switch, both...
  7. duke37

    dc-cdi 12/220 issue

    Q3 and Q4 should be the same. The circuit is symmetrical. Q3 has no pull down resistor so a mosfet will stay switched on, You need to drive it differently from a junction transistor. What is leg G?
  8. duke37

    dc-cdi 12/220 issue

    A snubber is a resistor and capacitor in series to absorb very high voltage spikes. You need an oscilloscope to set these up properly. A resistor between the inverter and C3 will remove the complete short but will waste energy. The value of the resistor should be determined so that C3 is...
  9. duke37

    dc-cdi 12/220 issue

    Transformer pins 4 and 5 should go to the 12V supply. If these are right, the other connections are probably right also. Q5/C3 seems very strange, it puts a short across the output of the inverter. This may be all right with a self oscillating circuit which will shut down with a short but in...
  10. duke37

    Switch and pot replacement for drill motor

    You will not find a pot which will take the motor current, it cannot be in the neutral line. You could use a light dimmer to reduce the voltage to the motor.
  11. duke37

    dc-cdi 12/220 issue

    I calculated that the frequency is about 48Hz, about right for the transformer. The transformer seems small, I think that the transistors should be able to pass whatever the transformer can pass. Have you got pins 4 and 5 connected to 12V? A 1000μF capacitor across the supply would be no bad...
  12. duke37

    dc-cdi 12/220 issue

    By CDI I presume that you mean capacitor discharge ignition, is this so? The 555 may not produce an equal on/off waveform. When a TIP122 turns off the energy in the transformer has to go somewhere and when two TIP122s are present, the opposite transistor may take this energy so giving a lower...
  13. duke37

    12V Battery on a 230V/50Hz Pump

    There are plenty of 12V water pumps on ebay, both high and low pressure.
  14. duke37

    Radio frequency interference with digital medical systems!

    433MHz is used by lots of devices, car keys, door bells etc. Interference could cause lack of operation or incorrect operation. I heard of a radio amateur who switched on his 70cm transmitter and blocked all the radio car keys in the supermarket car park. The M1 motorway runs past the now mostly...
  15. duke37

    Can a clock pendulum be slowed down by adding a resistor to the PSB?

    The compound pendulum seems the way to go. Make a pendulum with a cross arm with a weight at each end. This could be hid behind the 'clock' face and will increase the moment of inertia. There may be trouble with the pivot if made of plastic due to the increased loading.
  16. duke37

    IR Temperature sensor -> Multicolored LED

    Get a sensor with an output proportional to temperature to give a voltage in a convenient range. Feed this in to an op-amp with the other input maintained at the required reference point. Use a dual power supply with the two leds connected to ground, one running from positive and one negative...
  17. duke37

    Hovering Drone....W/Kg Calculation.....

    The energy required will depend on the rotor design. Aircraft produce thrust by throwing air backwards, this is matched by the wings pulling air forwards. The thrust as @AnalogKid says can be done by throwing a lot of air back at low velocity or a little air back at high velocity however the...
  18. duke37

    Power for 12v water pump

    I do not know what you mean by 'convertor'. It could be a transformer giving 12V AC or a power supply giving 12V DC. The pump may be fussy as to the power. A universal motor (simple electric drills) can often be run on either AC or DC. The residual current breaker should be positioned at the...
  19. duke37

    Methods to reduce wall power current?

    If the device has a thermostat, then reducing the power input will extend the ON time to compensate.
  20. duke37

    How to calculate run time of inverter

    I can not answer your question, I have no experience. The battery will be less efficient at high discharge and charge rates. Charging is nomally controlled by voltage, not time.
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