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  1. duke37

    2:1 ratio step down transformer question from newbie

    *Steve* "It turns the transformer into a current transformer, and without load the voltage on the transformers other winding will go extremely high." I do not understand this, with a 240V to 50V transformer, 50V on the secondary will produce somewhat less than 240V on the primary. No load...
  2. duke37

    2:1 ratio step down transformer question from newbie

    I would think either transformer would do the job. If you have a Maplins close, they should have one and you would save postage. The primary is not used and should not be connected to anything BUT it will bite. Have you thought of just putting a resistor in to drop the voltage, some...
  3. duke37

    2:1 ratio step down transformer question from newbie

    Yes, that is the idea. By connecting the primaries in parallel, the secondary voltages must be similar. Connecting them in the correct phase, will give the same effect as an auto transformer but with lower efficiency since the power has to go out of one transformer and back into the other. In...
  4. duke37

    2:1 ratio step down transformer question from newbie

    Pulse transformers are no good at all in your application. The cheapest way may be to use a 24-0-24V (marginal) or 30-0-30V mains transformer without the primary connected. Your power is very low and such transformers for powering amplifiers are much bigger than you require. It will depend...
  5. duke37

    solenoid power boost

    I made a note of a circuit to speed up a relay some time ago. The circuit doubles the voltage on the relay by adding the capacitor voltage. It takes longer than normal to drop out as the capacitor has to recharge. You will need to size your components appropriately to drive the solenoid. K1KP...
  6. duke37

    Marantz 4300 Update & question.

    A complementary pair will be one PNP (or P channel) and one NPN (or N channel). A matched pair will have similar characteristics but since the PNP and NPN transistors are made differently it is not so easy to match them.
  7. duke37

    Voltage measurement with differential amplifier

    If you set up a vitual earth op-amp, feed it with a constant current and use your variable resistance for the feed back, then the output voltage will be proportional to the resistance. With only 1 ohm you will not get much output voltage, so will need to include a post amplifier. Your...
  8. duke37

    Logic Gates

    You do not need to amplify the output of a comparator. If you only get 1V out, I assume that you have not fitted a pull-up resistor. See the circuit I posted earlier.
  9. duke37

    Part Number Help - MO305512

    This is possibly a triac. Is it fed with a diac (looks like a diode).
  10. duke37

    Back EMF of an electric motor.

    I think the answer must be yes but there are many, many types of motors out there. A motor works as a generator when it is turning, producing the back EMF. The current consumed depends on the difference between the supply voltage and the back EMF and the motor resistance. Applying a 'load'...
  11. duke37

    Resistors?

    Cars in the UK used to have this system of varying brightness, it was disastrous. I suggest that you have a full brightness led(s) for your rear light and then add extra leds in a different position for the brake light.
  12. duke37

    Can I Replace this AC motor?

    Plain bearings in motors such as this do not normally screech, they usually bind and become stiff. If there is a screech, perhaps the bearings have worn so that the rotor is touching the stator. You have nothing to lose by dismantling and having a look.
  13. duke37

    Triggering relay with 12v

    Draw your circuit showing the relay and the 12V power supply.
  14. duke37

    Can I Replace this AC motor?

    Does the motor spin freely? If the motor is stiff the thermal overload will trip. After 20 years, the bearings may need attention. When you have done yours, you can come and do mine!!
  15. duke37

    Logic Gates

    If you put 9V and 12V on one output, the supplies will fight to gain superiority. With luck, you have not damaged anything. I attach a diagram of my idea. One fet feeds the fan with a resistor in series and the other feeds it direct. Please comment. Please add a T to unsabilised!
  16. duke37

    some sort of resettable switch

    Here is the idea, you can take output from a second set of contacts or from the relay coil supply.
  17. duke37

    Nuclear Plant help

    And I helped develop the magnox fuel element cans for the natural uranium fuelled, high pressure carbon dioxide cooled, graphite moderated reactors. That was a long, long, long time ago.
  18. duke37

    Logic Gates

    That seems very complicated. You could get rid of the 9V supply and the relay by putting the motor in series with a resistance and switching this with a fet fed from one of the comparators. The other comparator would switch another fet to bypass the resistance. No other logic would be needed...
  19. duke37

    some sort of resettable switch

    Electric motor contactors - those with a red and green button - will stay off if the power is interupted. This is probably overkill for your purpose You can make a small one with a latching relay, here the problem would be to obtain or make a safe enclosure.
  20. duke37

    Nuclear Plant help

    I did not say that the moderator slowed down the reaction. I said that the moderator slowed down the neutrons to nearer an optimum speed so speeding up the reaction and if it is got right will be self sustaining (critical).
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