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  1. duke37

    relay switch between wash machine and wall outlet?

    The device to use here is a motor contactor, the type with a green button to go and a red button to stop. They have facilities for external buttons and your tilt switch would go in series with the red stop button so that when vibration gets excessive the machine stops and stays stopped. The...
  2. duke37

    Linear RF power amplifier

    Hi Dave, To get the temperature down, you will need to substantially increase the surface area, I woild look to double it. A big heat sink fitted to each side with self tapper screws would do. The alternative would be to fit an external fan. Only a small increase in air movement can have a...
  3. duke37

    Reading LM35 with AD0804

    I can't look at videos but, looking at your diagram, you do not have any capacitors to bypass the power supply. Looking at the national data sheet it seems as if the LM35 is prone to oscillation. They show the device connected to an A/D convertor with a resistor and capacitor damper to stop...
  4. duke37

    No signal on awa MHDV245503

    There are references to AWA MHDV2445-03 on Google, including a manual. I've not time to read them at present. Duke
  5. duke37

    Make triangular wave using 555 timer

    There will be a triangular or perhaps sawtooth waveform on the capacitor in a 555 timer. Any loading of this signal will upset the oscillator, an integrator on the low impedance output would be preferred.
  6. duke37

    Headphone Repair Question

    Wihout a meter you make things difficult but if you have an assistant, you can get them to hold a couple of wires to a single cell and you can then flick these across the plug contacts to make a noise. One technique that I have used is to try to pull the wire out of the cable with a pair of...
  7. duke37

    Headphone Repair Question

    Measure the resistance between body and ring also body and tip. If there is no connection, that is the one to investigate. The phone will click from the voltmeter current if it is working.
  8. duke37

    DC Power Supply (5V 10A) - Questions

    Your circuit is wrong, you have three resistors in parallel. you need only one. You need a low value resistor in the emitter of each transistor to ensure current sharing, dropping say 0.5V at maxixmum current.
  9. duke37

    A diode for my heating/hot water?

    The pump will not run with a relay coil in series with it. What proposals do you have for safe installation of mains supply? Duke
  10. duke37

    Isolate the output of a simple low pass

    What you have is an integrator which can be made with an op-amp and will give a low output impedance. The output voltage will not be much different if you make R2 larger, say100k. This is what Bob's solution does. Stick with R2 1k, the waveform should be the same but of half ampltude. To bring...
  11. duke37

    Analyzing large circuits

    You say, I think I have an fair idea of what's going on. A question for my own sanity though, doesn't the main current (the one not generated by the inductor) charge the capacitor? So if the inductor was to release the energy, wouldn't the capacitor be at it's limit? Or does the capacitor...
  12. duke37

    Analyzing large circuits

    Basically yes but inductors do not generate energy, they store it. The diode across the relay coil will pass current until the resistance in the coil will dissipate the energy and the current dies away. If a capacitor is placed across the coil, on switch off, the energy in the coil will go...
  13. duke37

    Analyzing large circuits

    You asked about the energy in a capacitor and the choice of capacitor size so I thought I would give three similar equations for energy, the hammer analogy is very good to understand the voltage when switching off an inductance and the necessity of using a flywheel diode or capacitor to limit...
  14. duke37

    Inverter 12dc/222v

    Post a copy of your circuit, look up the pin configurations on the internet. If a power fet is getting hot, either it is asked to pass too much current or it is not being turned on fully.
  15. duke37

    Analyzing large circuits

    You can get round to understanding this stuff by working up gradually from simple circuits to slightly more complicated ones and to try to repair those that go wrong. Logic and method is the way to go. You say that you have seen a circuit with three capacitors in parallel although one was...
  16. duke37

    A diode for my heating/hot water?

    Take note of what Dave D says. Your simplest solution is to insulate the hot water tank properly so that it does not matter that the heat is on all the time. You cannot use a diode to make a one way control on AC, you will need to use a relay which is wired correctly, get the wires crossed...
  17. duke37

    VCO

    What about the ICL8038?
  18. duke37

    Motor Driver works with PS, not battery

    I've never used such a chip but looked it up. The chip is very fast and will be sensitive to external spurious signals. Try some fat electrolytics across the power supply.
  19. duke37

    Motor Driver works with PS, not battery

    Very strange, perhaps you could post a circuit diagram and specification of a good and bad supply. Is it something simple like providing the wrong polarity?
  20. duke37

    Heated Mattress Pad Problem

    In the UK the fire service occasionaly arranges for electric blankets to be tested since they are often a cause of fires. Anything over a couple of years old is suspect. I would not use one if it is turned on and I am now too old to always remember what I have done! You can check whether the...
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