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  1. duke37

    Newbie needing help - arcing relay

    The relay is driven by 12V DC, I would check that this is consistent, allowing the relay to stay in. Something is upsetting the relay when it should be conducting. Is the temperature controlled by switching the power on and off rapidly? I would not advise a newcomer to measure when it is...
  2. duke37

    Newbie needing help - arcing relay

    If the relay is arcing when it is supposed to be hard on, then look at the relay coil supply to ensure that the contacts are closed. A more powerful contactor will only push the problem elsewhere if it is due to an intermittent signal.
  3. duke37

    Badminton Scoreboard Build

    pradoartz Where did you get the type face? It is smaller than the standard used here but I find it much more readable. Thank you
  4. duke37

    Dont want to blow up my welder.

    I do not understand the story. What you need is an alternator capable of 5kW plus. A welder is a horrible load and an alternator may not be able to handle the variations. Also the invertor rectifies the mains which distorts the waveform. One alternator that i played with needed a 2kW resistive...
  5. duke37

    Circiut knight rider

    D2, D3, D4 and D5 have two inputs. One input will be high and one input low. It is anyones guess which will win. Disconnect one input on each of the LEDs to see if they still work. If you wish to drive a LED from more than one supply, then a diode (1N4148, 1N914, !N400* etc) in each output can...
  6. duke37

    heat emitted by LED signs and lights.

    The heat emitted can be estimated from the power input. Most of the input will be output as thermal energy, some will come out as light.
  7. duke37

    Braun Shaver 7526 Circuit Board

    Has one of the big electrolytic capacitors got a domed top?
  8. duke37

    Braun Shaver 7526 Circuit Board

    Seems as if you have connected the batteries the wrong way round. If you are lucky the resistor and diode will have done their job without failure. You can test both components with a simple meter. Does it work with the batteries connected correctly?
  9. duke37

    Submerging a CoB LED

    I think you will have problems. 60W will probably cook your fish unless the aquarium is very big. You could use a copper bar or pipe with the LEDs soldered to it for heat sinking and then pass cold water through the pipe to take away the heat. The assembly could be placed inside a plastic bottle
  10. duke37

    High voltage: Can't stop electricity from jumping over resistors

    If you see sparks, then the oil does not have sufficient insulation. I have had trouble with a sense resistor taking 1mA from a 5kV supply. I used various resistors until I found that some 1MΩ resistors from 1930 were quite happy. Your application is ten times more severe so to limit the voltage...
  11. duke37

    Portable Power Supply

    Any linear regulator will have the same low efficiency as the LM317T. To get more efficiency, use a buck convertor with the full battery voltage on the input. Should get at least 80% efficiency. This will be much simpler than splitting the battery. The convertor will regulate voltage, if you...
  12. duke37

    Pressure Plate Project

    Your main problem will be the mechanical design and build. You could use an antique balance as used to weigh sacks of grain or coal. You could consider the use of Bellvile washers as a spring which has a self-limiting movement. This could be quite small.
  13. duke37

    Pressure Plate Project

    Use a strong spring with stops to limit the movement and use the movement to operate a microswitch. You do not say how sensitive it must be.
  14. duke37

    motor run-capacitor testing and identification

    Some motor capacitors have a high value resistor buit in to discharge the capacitor when exitation is removed. This could be measured with a meter. Looks as though it is shorted. 6,3 is used in some countries for 6.3
  15. duke37

    I Need Help With My 555 Monostable Circuit Please

    Remove the motor and replace with a led and resistor i series to check the time of the 555 pulse.
  16. duke37

    9v Guitar Amp w/out LM386

    ?2 puts 8Ω across the battery/ It will not last long with a drain this high. Remove the link. ?1, the capacitor should be connected across the battery.
  17. duke37

    Looking for a replacement of NE38B Neon Indicator Bulb

    High value resistors can often go up in value, if these are in the feedback, then more voltage than intended will be generated. If the neons are the voltage reference and it is much too high because they are open circuit, then the output voltage will be too high. I did not spot the rectifiers...
  18. duke37

    Short Wave Radio Project Help Needed

    Just use a 7809 or LM317T to drop the voltage from 12 to 9. The radio has a regenerative circuit. If this goes into oscillation it will affect other radios in the vicinity You will need a licence to transmit.
  19. duke37

    Looking for a replacement of NE38B Neon Indicator Bulb

    Check your 22MΩ resistors. There will be a feedback circuit somewhere to set the voltage. If the EHT circuit is producing AC rather than DC then nasties will occur. Check rectifiers and reservoir capacitor.
  20. duke37

    7815/7915 Power Supply Issue

    It sounds as if you do not have a good common connection. If the +15V load is the same as the -15V load, then the common will sit in the middle and all looks well. If the loads differ, the common gets pulled to one side. I do not understand why you get a total of 18.4V rather than 30V. Can you...
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