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  1. duke37

    Got a question about driving LEDs? (Another work in progress)

    Steve I think the thread is pretty good as it stands. It is difficult to give one explanation to those of very different abilities. It is often necessary to explain in several ways before the penny drops, when it does, it is very satisfying. One of the problems is to explain that there are...
  2. duke37

    Ferrite core turns

    It is the number of complete turns, count the number going through the core i.e. seven,
  3. duke37

    Voltage regulator for High power LED's

    Flashdom Early on you made some remark about complexity. The constant current source will give a very consistent light output but I doubt if this is what you require. As I pointed out earlier, with a 317 you need at least 4.25V across the regulator circuit. With this amount of voltage drop you...
  4. duke37

    about voltage follower op amp

    If it is working OK then adding an op-amp will not help, don't complicate matters if it is not necessary. The sensor will have a low output impedance, lowering this further with an op-amp near the sensor will make little difference. The temperature sensor will not be able to respond to very...
  5. duke37

    230v sub. well pump

    There must be two wires, one out and one back. These are normally called line and neutral. In the UK two wire devices without ground are permitted if the insulation is to a high standard and the case is insulaiting. You could show a diagram of the connections.
  6. duke37

    Voltage regulator for High power LED's

    Get a data sheet on the LM317T, this will give details on how to use it. Controlled voltage. The 317 is designed to produce a controlled voltage, it raises the output voltage until there is 1.25V between the output and the sense pin and controls it there. The resistors are chosen to give...
  7. duke37

    Help with parts for Voltage regulator

    The necessary difference between input and output is called the dropout voltage. I have an old RS calalogue and this shows a MIC2941ABT regulator with a dropout voltage of only 0.6V, It will supply 1.25A. I have not checked the data sheet. You could trawl the web for information on other...
  8. duke37

    Relay socket help

    It looks to me that the connectors are the standard quarter inch spade connectors. The clips as shown in the photo are available at any auto suppliers. The block is a housing to insulate one connector from another. You could make something from insulating board and epoxy resin glue.
  9. duke37

    Voltage regulator for High power LED's

    Look up the data sheet for the LM317T regulator, this can be configured for constant voltage output or constant current output. It is a linear regulator so dissipates some power. Swiching regulators will dissipate less power but need more designing.
  10. duke37

    Help with parts for Voltage regulator

    I had alook at the LM338T data sheet. You need about 3V more input than output to give a few amps. So, to get 6V out you will have to provide 9V in which could be provided by three batteries.
  11. duke37

    Need stepper motor that goes 6 deg/step for clock project...

    Or use the 1.8 deg/step and 200 pulses per revolution?
  12. duke37

    Another Newb LED Question

    OK to be specific. Four leds at 3V each in series equals 12V. Battery equals 12V. Result no cuurent. Battery equals 12.1V. Result high current, leds get hot and drop required voltage to 11.9V, very high current. You now have 0.2V across very litle resistance. Adding a 50 ohm resistor will...
  13. duke37

    Another Newb LED Question

    There is a "sticky" by Steve giving details of how to drive leds. In short, you need a resistor and sufficient voltage to drive current through it. The reason for the resistor is that the power supply can vary and the voltage across the leds will vary with temperature, the higher the...
  14. duke37

    Fine Adjustment Control for Welder?

    A complex solution would be to replace the rectifiers with thyristors but this would cost a lot and need a lot of circuit develpment. I would suggest adding a resistance in the output lead and running on the highest setting. The resistance will have to be low and capable of quite a high power...
  15. duke37

    Reed switch fails within a few operations

    What is MIC DB107? Is this a bridge rectifier? A reed switch can only switch a very low current at a low voltage. You are switching a 10uF capacitor and probably more capacitance in the PSU. This will blast the reed switch contacts as they charge. Possible solutions 1. Use the reed switch to...
  16. duke37

    Something simple...

    The capacitor is charged every 1/120 sec. The rate of change of voltage on a capacitor is I/C so with 1A and 1mF, the voltage will drop about 8V, with 10mF it will drop less than a volt. Things are quite complicated since the motor will only take current when the applied voltage is greater than...
  17. duke37

    Touch sensitive transistor latch; erratic behaviour and other problems

    The 'thyristor' has a very high gain and once it starts to turn on, it switches fully on rapidly. A rapid rise of input voltage will set it off due to capacitive effects. Thyristors are specified for maximum speed of voltage rise. To make the pair less sensitive, place a resistor across the...
  18. duke37

    Automatic chicken coop door opener

    Yes, a counter/timer could be used to check whether the light level was low for more than a specific time. This would take you (but not me) into the world of microcomputers.
  19. duke37

    Picking transistors

    Your transistor appears to have got lost! The maximum current taken by the transistor will be limited to about 0.1A peak. that is +/- 0.05A peak or 35mA rms. Putting all of this into an 8 ohm speaker (I*I*R) gives a power of about 10mW.
  20. duke37

    well water level measure

    It is fairly easy to produce an audio frequency which varies according to the resistance of your potentiometer. If you can get one of the mains connected baby alarms, then a frequency to voltage convertor could give an indication of water depth. If you have three wires with no neutral then the...
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