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  1. duke37

    Hijacker needs help (LED traffic lights)

    I made one to drive a single light which included a red and amber phase. The 4017 drove three fets which could switch 5A at 12V. It is on this site somewhere, I could try to find it if you are interested.
  2. duke37

    Pulse Transformers

    You could look at TV and computer power supplies, possibly take one and rewind the transformer output to the voltage you require. You will need fast high voltage rectifiers and low ESR capacitors. An push-pull inverter would be easier to design, could be run at a lower frequency and would be...
  3. duke37

    27MHz colpitts oscillator qestion

    I have not used Multisim but would like to make the following comments. 1. The supply is not bypassed, this will not be a trouble with an ideal battery. 2. The tuned circuit has a very low impedance, I would expect the reactances to be 10 or 20 times the values that you used. 3. The base is...
  4. duke37

    Is there a way to measure voltage without losses?

    I presume that you need to measure the voltage of a battery with 22 cells in series. A digital voltmeter with an input resistance of 10M will take very little current which will be lower than the battery internal loss. Analogue meters will take much more current depending on the movement...
  5. duke37

    Pulse Transformers

    The quick answer is no. Mains is a sine wave at 50 or 60Hz and nothing like a pulse. To get isolation you will need a transformer, either a 'massive' iron cored transformer or a high frequency ferrite cored transformer fed by a switching circuit. The pulse transformer MAY work in the latter case.
  6. duke37

    Truck lighting question

    Have you connected the brake light 'upside down' so that when it is lit it also supplies power to the other lights? Check that the bulb outer is always at ground.
  7. duke37

    Regenerative braking dc motor controller

    That is the sort of thing that is necessary. Use a P channel fet for M3 as 'steve' said. I do not think you need D3. A capacitor should be connected across the motor to take account of the high frequency load.
  8. duke37

    Truck lighting question

    But is the common ground solidly connected to chassis? Take a wire from here and check that it is always 12V away from the battery positive or 0V away from battery negative.
  9. duke37

    555 metronome with leds

    A 555 gives an asymetrical output in that circuit. I am no expert on the 555 but I think that a symmetrical output can be obtained by disconnecting pin 7 (discharge) and connecting R1 to output instead of Vcc.
  10. duke37

    Op-Amp premature clipping

    As you say, an ideal op-amp can be considered to have the two inputs at the same voltage, also, it takes no current to drive it. In your case, the + input is connected to ground so the - input will be at a similar voltage (plus op-amp noise). The - input will then look like a ground and to...
  11. duke37

    DC circuit help

    You could make an oscillator with a 555 or 4093 with care to get the longer times, this could switch a changover relay. You will then need two powerful cross connected contactors to switch the supply.
  12. duke37

    Wind turbine project, wiring, etc.

    You will have a limited amount of room to put the winding in, so you have the choice of lots of turns of thin wire or a few turns of fat wire. The voltage per turn will be the same so if you have twice the number of turns, you get twice the voltage but the wire must have half the area so can...
  13. duke37

    Oh what to do with a Tetrode tube????

    Most of these tubes need to be operated vertically or the hot filament can sag and contact the grid. Some tubes can be operated on their side with the grid vertical so the sag does not reduce the grid/filament spacing.
  14. duke37

    Op-Amp premature clipping

    The circuit that you show three or four posts back, is a virtual earth amplifier. If you have plenty of gain, there should be negligible voltage at the input. As explained previously, the amplifier is controlled by current input. The gain will be R3/input impedance. Try a 1k in series with the...
  15. duke37

    Repairing RC Hummer - MOSFET replacement

    The 2SK 3435 seems to be a very good switching transistor but the others should do. 'Honest guv, I never put the battery in the wrong way round'
  16. duke37

    Repairing RC Hummer - MOSFET replacement

    The reference doesn't bring up the 2SK sheet. The IRF is very similar to the STP and should be OK. The capacitance is fractionally higher and the threshold voltage is also slightly higher. I don't think this should make too much difference. The FET has obviously gone pop with considerable...
  17. duke37

    What kind of switch do i need?

    The more poles you have, the more the current can be shared. I did not see the 5A rating, it seems a bit much to me for this type of switch. If you go for the 12 way, nine of the contacts will never be used. When you come to try it, I suggest that you connect battery A and see if it switches...
  18. duke37

    What kind of switch do i need?

    You will only need 1 pole, 3 way. The Maplin switch is 3 pole and the 3 poles should be connected in parallel to get the current capability that you are after. A 4 pole 3 way would be even better so that the curent is divided 4 ways.
  19. duke37

    Regenerative braking dc motor controller

    The motor will only act as a generator when it is spinning fast and producing over 200V. You need some circuitry to raise a low motor voltage to over 200V to recharge the battery. Trams and trains have used resistive braking because of the problem of getting the energy back into the supply...
  20. duke37

    Truck lighting question

    Many problems with vehicle lights are due to faulty grounds. If some other lights come on when the brake lights are activated, then these are providing the groumd connection for the brake lights. Check the ground to chassis voltage of the brake lights in the various conditions. It should...
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