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  1. duke37

    LM380N cuts out with loud input....sometimes

    It seems that you are overdriving the amplifier. I suggest you play some gentle lute chamber music. Alternatively, you could make sure the chip is kept within its rated temperature range by reducing the drive and increasing the heat sink size. Shorting pin 1 to pin 14 shuts off the bias...
  2. duke37

    how it works, how to calculate the output

    It says 2.5V ! The input voltage must be more than 3.5V and less than 15V.
  3. duke37

    Increasing Line 120VAC to 340VDC

    I have only played with electric fencers which have pulses of around 1J, triggered at each second. That is plenty to deter me from touching the wire. The capacitors are non-polarised pulse capacitors, electrolytic capacitors are not suitable. I was under the impression that the energy in a...
  4. duke37

    relay not working in comparator circuit

    The LM393N is shown in a catalog that I have but if you have a 741 I would stick with that. A small amount of positive feedback (pin 2 to pin 6), maybe 10M resistor will give a dead band to stop jitters.
  5. duke37

    Increase volume of simple ribbon synth?

    You will not get much volume with only a 1.5V battery.
  6. duke37

    How to calculate output voltage for ac coupled inverting amplifier

    mursal has given the formula, you should be able to evaluate that. The op-amp cannot provide more voltage than its power supply voltage so 2.337kV (not 2.337KV !) is absurd. With an output swing of 1V, the maximum signal input would be 1/714 = 1.4mV
  7. duke37

    LED fixture build help

    The resistor was calculated to drop the required voltage at 650mA (not 650ma !). If you want less current, the resistor will be higher. If the power supply can maintain its voltage, it does not matter whether it is rated at 1A or 100A. It just needs to be powerful enough for the job.
  8. duke37

    How to calculate output voltage for ac coupled inverting amplifier

    The gain of a virtual earth amplifier is just output resistance divided by the input resistance, in this case 40000/56 = 714. There are two things to be considered;- 1. The operational amplifier must have a gain much higher than this. 2. The input capacitor will provide a significant...
  9. duke37

    Increasing Line 120VAC to 340VDC

    Yes, The mention of a laptop power supply threw my thinking off line. If isolation is not required, then a voltage doubler from 120V mains would do without a heavy transformer. Excellent insulation would be needed. The doubler would consist of a capacitor and two diodes only. It would...
  10. duke37

    Increasing Line 120VAC to 340VDC

    200J each second = 200W The power supply you suggest is only 66W A boost converter to go from 19V to 400V may perhaps be purchased or made. Do not expect an efficiency of much over 60%.
  11. duke37

    LED fixture build help

    I presume you mean 650mA (0.65A). mAh is a measure of energy such as in a battery. The current in a series circuit doesn't need to be spread across the LEDs, it will be constant throughout the circuit. My calculations are different from yours. 6 * 3.4 = 20.4 Voltage across resistor = 24...
  12. duke37

    9V bat. backup for 5V circuit

    A schematic of what you suggest would be helpful. A regulator should not take much current. I have not looked up the specification of the LM317 but the control current is so small that I neglect it. A 7805 will need a few mA in the control connection so this is not for you.
  13. duke37

    relay not working in comparator circuit

    The 741 can not output a high voltage at a high current. The output voltage will be the battery voltage less the drop in the 741, less the drop in the base resistor,less the drop in the 2N2222. To help things, put the buzzer/relay in the collector of the transistor with the emitter connected...
  14. duke37

    SCR question

    A popular small SCR is the C106M. (400V, 4A) This drops 2.2V when on. It needs 20mA through it to start. It needs 3mA to hold on. I would think your devices would be similar.
  15. duke37

    SCR question

    A SCR and relay do different things The SCR will turn on but not turn off like a relay unless it is switching AC. A SCR will need over a volt across it to work. This may give too much loss in a low voltage circuit A SCR needs a minimum current to hold on, 0.7A should be plenty, look in the...
  16. duke37

    Continuity or infinity on a starter?

    The starter will take a very large current. You will need a big battery and fat cables to feed it. It will take off like a scalded cat and spin off the bench unless you tie it down. A headlight bulb in series with the starter can be used to see if it is taking current and probably indicate...
  17. duke37

    Resources

    You do not say what country you are in. The systems and regulations differ significantly, voltages, earthing, current limit, cable sizes, protection systems etc. In the UK you can go to the local library and borrow a copy of the current ! regulations. The law here allows non professionals to...
  18. duke37

    water level indicator

    There will be no danger if you are using an isolated 12V supply. The 180k resistors could be raised to say 1M if necessary which may make more reliable operation. The 2.2k feeding the BC148 is very low. The BC148 could be replaced by a fet or a darlington transistor with a high value drive...
  19. duke37

    Wiring Question

    So, you have two plugs in parallel, connected to two sockets. Taking one plug out will give you live pins - very dangerous.
  20. duke37

    Wiring Question

    In the UK this bodge would be illegal because of cross feed to an apparently turned off circuit. If you have two plugs connected in parallel, you will have live bare pins. Its been nice knowing you. Use two feeds, one to power all the low power devices and one to supply the high power devices.
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