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  1. duke37

    Oscillator Query

    The tank circuit has an inductor and two capacitors in series. The current is flowing one way then the other at the resonant frequency. During one half cycle, the current will be flowing out of C1 and flowing into C2 so the polarity will be opposite. If the values of C1 and C2 are the same, the...
  2. duke37

    Oscillator Query

    The tank circuit is tapped near the middle with the two capacitors. When one end goes positive the other end goes negative, like a see-saw, that is 180 degrees. The transistor adds another 180 degrees.
  3. duke37

    Detecting water level and pumping it out

    Three things. 1.Stainless steel would corrode less than copper. What are metal guitar strings made of? 2. A transistor can have a current gain of 500 or so. A Darlington transistor can have a gain of thousands. A fet can have almost infinite current gain but they are a bit too...
  4. duke37

    Lighted LED base repair

    You did not say anything about a blue led. You should take it out and test it and replace if faulty. Temporarily tacking on a led of any colour will determine if the circuit is working.
  5. duke37

    AM Transmitter

    A baby alarm is a microphone and low powered transmitter which is put close to the baby. If the baby wakes and makes a noise, the transmitted sound can be heard on a receiver in another room. I Googled 'pantry transmitter' and got some hits. Most of the vintage-radio ones use valves but I am...
  6. duke37

    AM Transmitter

    Some people have made very low powered transmitters to activate old valve radios on long and medium wave. These have been given the name of pantry transmitters, look on the net. Some use valves (tubes) and some use semicoductors. 200m range would put them well into the illegal area in the UK...
  7. duke37

    OP AMP Wiring help please

    A voltage follower should work to reduce the discharge rate of the capacitor. The very nice picture you show is incomplete, you need to show all connections
  8. duke37

    Lighted LED base repair

    I think the black blob is the 'driver'. If the leds stay lit, this is not turning the current off. Bad news ! The leds work so are OK.
  9. duke37

    Need ALOT of help on an interesting project.

    Traffic lights in the UK often have vehicle detectors to optimise the light timings. These are coils which are embeded in the road surface by cutting a slot with a diamond saw. The coils therefore are rectangular. I do not know how the detection circuit works or how you would protect against...
  10. duke37

    Need help troubleshooting a Mentor DC Drive for an extruder

    Where are you located? What are you extruding? Without looking back at the diagrams, I think the field has a controlled curent, thus any leakage in your cables will give less current at the motor. As I said previously, you can get an idea of the field exitation by measuring the voltage and...
  11. duke37

    Help! Fixing Buzzer System

    The power supply can not provide sufficient current so the voltage sags. The problem may be in the power supply or the load. Look at the rating on the power supply and use a resistor to load it close to the rating, see if it can maintain voltage. The spark indicates that there is a large...
  12. duke37

    astable multivibrator

    You refuse to show us the schematic with component details. A 12V supply is too high on a simple cross coupled multivibrator, it generates a negative emitter/base voltage which should not be more than 5V. iimagine I do not think that the circuit could be so accurately balanced that it...
  13. duke37

    Need help troubleshooting a Mentor DC Drive for an extruder

    If the equipment works correctly at speed, then the power side is likely to be correct and the fault is in the control side. The KTK only controls the field and the voltage across the field should be measured. If there is a poor connction, then this does not necessarily give the current but...
  14. duke37

    Need help troubleshooting a Mentor DC Drive for an extruder

    I have had a look at the data you sent. The KTK supply which we had just had a 0-10V signal for speed and another for torque, non of this computer nonsense. It seems strange that KTK can't spell their address ! I would think that there is too much armature current and looking at the data...
  15. duke37

    astable multivibrator

    Show us the circuit including the supply voltage and the active devices. I presume you mean 100µF not 100mF, they would be a BIG capacitors.
  16. duke37

    Amplitude and Frequency

    Bells used to be made to clang. Quite recently, perhaps 100 years ago, it was found how to tune the various vibrations to get a harmonic chord. A lot of church bells have been recast and tuned to make then sound sweeter. The Big Ben clock bell has a crack so will never sound sweet.
  17. duke37

    LM317T Adjustable Voltage Regulator HELP ?

    The 1N4007 will do all that the low voltage 1N4002 can do and then some ! The diode is there since when the power supply is turned off, the input voltage may fall faster than the output voltage. The reverse voltage on the 317 is not welcome.
  18. duke37

    Need help troubleshooting a Mentor DC Drive for an extruder

    I have used a KTK drive some years ago, supplying both field and armature. My uncle had his car run away down Vastre hill and arrived in Newtown at high speed. Luckily he hit nothing and the sheep in the trailer went to market as intended. I presume that you have cleaned the commutator of...
  19. duke37

    1 Wire GM Alternator and Generator Light

    What does the idiot light do? I think the earlier alternators used separate rectifiers to check if the alternator was producing a voltage. A LM3914 bargraph display will act as an accurate voltmeter with 10 steps. This can be used to drive an idiot light directly. A ferrite sleeve over the...
  20. duke37

    Car Battery Load Test Results (Is this good or bad?)

    It all depends on the vehicle. I used to have a Sunbeam Rapier, the batteries only lasted a couple of years. My used batteries went to my sister's Austin A35 and lasted many more years. My brother had a Ford diesel which was a terrible starter. The local garage replaced the thin cable from...
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