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  1. duke37

    Help with an R2-D2 LED Circuit

    It is difficult to help at a distance. It seems you are still going with the three transistor cicuit, prhaps we now know what happens. try reducing to two transistors. You do not say what transistors you have. You could try going to Darlingtons (I use MPSA13) whih have a colossal gain but a...
  2. duke37

    3V to high voltage inverter

    One source of low voltage to high voltage convertors is the flash circuit of disposable cameras. There was a shop near here which would develop the films while you waited. I asked for a couple of cameras and was given two, complete with good alkaline batteries. I was told to be very careful and...
  3. duke37

    Help with an R2-D2 LED Circuit

    I was suggesting a resistor from the collector to the positive of the supply to pull up the collector when the transistor is turned off. I do not see any part of the circuit which has more than two leds on a transistor.If the leds are in series there will not be enough voltage to turn three...
  4. duke37

    Help with an R2-D2 LED Circuit

    I cannot see anything wrong with your circuit. The two transistor circuit on the right should be fine, I am not sure of the effect of going to the three transistor circuit. Beware that there is a strict limit to the emitter/base voltage of a transistor. Your circuit generates slightly less...
  5. duke37

    purchasing a transformer

    I would agree with Harald. If you are going to purchase large quantities, you need more information than you have given. Make one and see if it will do the job. Does it overheat? Does the insulation break down? Is there too much interwinding capacitance? Is there enough coupling? Will...
  6. duke37

    Relaxation oscillator Noob need education

    It looks as if you have a 1uF capacitor and a 20k resistor for the timing. Have you determined the frequency this will give you? If you connect the output to a load of 1.5ohm you will ask the op-amp to give out current many times what it is capable of. This may have killed it.
  7. duke37

    Repairing speakers

    Your first picture is too black to see anything. The second pictur shows a cable bent in a way that no cable should be bent. The tail is there to make the bend much less abrupt. You do not say what this cable does, you could remove it and measure the connections end to end and then if...
  8. duke37

    Repairing speakers

    Can you take a picture of the speakers and show the faulty cord. I presume that one speaker has an internal amplifier, is this so? What is the power supply? It sounds as if you have a bad connection, perhaps a cable has been tugged or it has been wiggled about so much that the wire has...
  9. duke37

    Remote Glow Plug Ignitor

    I have met a 555 but I am not on speaking terms! The trigger needs to go to less than one third of the supply voltage. Your switch will take it all the way down to zero so there will be no problem. The 555 can run on 7.4V and will not need a stabiliser, it could be driven directly from the...
  10. duke37

    Remote Glow Plug Ignitor

    1. The resistor could go up to 1M and the capacitor down to 10uF. This would be smaller and lighter. 2. The trigger voltage is inherent in the 555. you could add a transistor amplifier too make the inpit more sesitive but I do not understand why you should want this. A resistor from pin 5 to...
  11. duke37

    3V to high voltage inverter

    I could not get the link to work properly Have you got the transistors numbered correctly? The BC547B is 45V 200mA The 2SD506 is 100V 12A 150W Neither is the same number as you have and they are very different. The circuit looks strange to me with a resistor in the collector lead. Also...
  12. duke37

    Need help finding or crossing these components

    PIV = Peak Inverse Volts This is the maximum volts which the diode can withstand in the reverse direction. A 1N4007 can pass 1A and has a PIV of 1000V. You would need four to make a bridge. Selenium rectifiers were often used for low voltages. They degrade with time so an alternative is better.
  13. duke37

    Low Temp Effects on 555, 386, and TL082

    Mullard Reference Manual of Transistor Circuits. (1961) "Vbe decreases by roughly 2mV per degree Centigrade. This rate of change is almost constant for all transistors (germanium and silicon)." The book also deals with leakage currents but this is not likely to be significant with...
  14. duke37

    speed control of 2 x 110v 2kw angle grinder motors

    You could try a lamp dimmer circuit, this consists of a resistor, capacitor,diac and triac. A normal lamp dimmer will not be powerful enough so you will need a bigger triac. This will adjust the speed but will not control it with varying loads.
  15. duke37

    Switchable Cathode Bypass Capacitor for a Tube amp

    The 1uF capacitor will give a turnover frequency of about 100Hz, the 2uF capacitor about 50Hz. I think the gain will rise as the frequency rises and be limited to about 10 times the basic amplifier. If you wish to reduce the gain and improve linearity with a constant gain, then you can put a...
  16. duke37

    Low Temp Effects on 555, 386, and TL082

    The voltage drop of a semiconductor junction changes at about 2mV per degree Cent. An op amp contains a plethora of junctions so extreems of temperature could affect the operation even if there is no damage. There will also be leakage problems at high temperature but this should not be a...
  17. duke37

    Selecting Temperature sensor IC

    The venerable AD590 gives a current out proportional to temperature so cable resistance (two wires) does not affect the reading. A resistor at the receiving end would convert this current to voltage for an ADC. How does a one wire device work?
  18. duke37

    how to signal an alarm at point

    You could use sound, get a foghorn. You could use radio, get a radio controlled doorbell or a mobile phone. Distance measurement can be done by ultrasonics or laser but if it is not line of sight, I think it impossible as the definition cannot be specified.
  19. duke37

    Recharging a car battery

    A bridge rectifier consists of four diodes. One diode is not any more likely to fail as long as it is specified correctly. I doubt if you will get significant energy back from regeneration, you have to consider the efficiency of the motor and the control circuit. There are controllers for...
  20. duke37

    Recharging a car battery

    All old DC motors had wound fields and were used to drive trams, fairground cars (dodgems) or roundabouts. Large motors still use wound fields due to the cost of the rare earth magnets. Electric drills use universal motors which can run on AC or DC with the armature and field in series. If...
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