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  1. duke37

    LED driver - improper crossover filter?

    The top bank can only be driven with an alternating fequency coming from the amplifier. This could occur due to parasitic oscillation which can only be due to feed back. Three areas to be investigated are, 1. The microphone feed is taken from the + line with no extra smoothing, add an extra...
  2. duke37

    LED driver - improper crossover filter?

    The lower bank is fed by a low pass filter which goes down to zero frequency, thus the DC output of the op-amp will turn on the leds. To stop this, put an electrolytic capacitor in series with the LP filter with a cut off frequency of say 20Hz.
  3. duke37

    Component Question:

    Components are not ideal, selenium rectifiers leak, germanium rectifiers leak less, silicon rectifiers leak vey little. A Zener diode uses two mechanisms, Zener below about 5V and avalanche above 5V. Zener diodes will always leak a little and, when the voltage is high enough, the leakage will...
  4. duke37

    Velleman ignition amplifier K2543 making audible ticking noise

    Do not pot the box, there are several resistors dissipating quite a bit of power. These will overheat if they are not cooled sufficiently. Can you locate the source of the noise, say by using a hearing tube? I would use plastic, the circuit could bite if you use metal.
  5. duke37

    Velleman ignition amplifier K2543 making audible ticking noise

    If you have a noise, then you have a moving part! The circuit provides a high current pulse which can move wires due to the formation of a magnetic field. You do not say what your box is made from but a steel box will couple to the wires more than an aluminium box.
  6. duke37

    Audio Amplifier Project

    The idea of bridging amplifiers is to get twice the voltage across the speaker so four times the power. This is very useful when the supply voltage is low (12v car). A voltage can only be defined between two points, the input is defined between the input wire and earth (ground). The amplifier...
  7. duke37

    Urgent Help needed to get output of ac 5v 400hz frequency and current 500ma

    I last worked with LVDTs fifty years ago when new fangled devices called transitors were all the rage. I believe that you will need a signal of low distortion and with very constant amplitude since the output (distance measured) will be proportional to voltage. If you are to work in the...
  8. duke37

    Audio Amplifier Project

    I have not looked up the specification of the IC you are using, so what I say is only a guess. 1. The circuit will not work! The power + and - are both connected to pin 13. Your supply will object violently. 2. C2 is to reduce interference, it is a very small capacitor to by-pass radio...
  9. duke37

    power indicator

    You can't get energy out (light) with no power in. Why not connect to the terminals? Why use a led? The way I would do it is to connect a neon indicator which can be obtained with a built-in resistor or can use an external resistance. This is the type of indicator in a magic screwdriver.
  10. duke37

    Identify this capacitor

    I would think that any non-polarised capacitor would do with a voltage capability of 75V or greater and of the right capacity. Are you sure that it is faulty?
  11. duke37

    Power supplies, inject current to its output

    Power supplies are normally made with rectifiers so will not accept reverse current. I expect that the currents you generate are very low so it is only necessary to load the power supply with a resistance taking more than the generated current to get a working system. You will need a...
  12. duke37

    tesla coil spark length

    I have not played with super high voltages but, in the case of electric fence energisers, the figure of 3kV/mm seems about right. Surely this is the electric field strength. Mr Volta would like his name spelt with a capital V.
  13. duke37

    IR Proximity sensor

    A 10k pull up resistor would be adequate when driving a fet and 12V is ideal to turn it fully on.
  14. duke37

    tesla coil spark length

    The Tesla types use 3000V/mm I believe. If the output voltage is not as expected, perhaps there is insulation breakdown inside the gubbins. Have you got the primary and secondary resonance the same? I would doubt if the coupling is very tight.
  15. duke37

    help needed

    I've Googled 'seed flow monitors' and there are systems based on vibration and optical blocking. Simba Horsch do a drill with optional monitors. It depends on where the blockage is but have you thought about pressure detection?
  16. duke37

    multi direction dc motor

    Yes indeed Bob, great minds think alike! If you change the high side transistors to pnp and connect the inputs of the resistors of the two left transistors together, when the input is high, the npn will be on and the pnp will be off. Doing the same on the right hand side, driven in...
  17. duke37

    multi direction dc motor

    Nice clear picture. I thought that this may be the circuit you are using. A NPN transistor needs the base to be more positive than the emitter to pass current. The 'high side' transistors if driven by 5V will have less than 5V on the base depending on the resistance and the emitter will be 0.6V...
  18. duke37

    unknown formula

    Except that there are not two transformers, only one. There are two windings.
  19. duke37

    Clapp Oscillator

    Yes, AGC is automatic gain control. In the days of Mr Clapp, the valve (tube) would take gid current which would bias the valve to take less current so restrict the amplitude. A similar method has been used with a diode on transistor oscillators. Variable resistors such as varistors or filament...
  20. duke37

    traffic lights

    You will need to generate a logic sequence for the lights. In the UK we have red, red +amber, green, amber, red. I believe that there is no red + amber phase in Australia. I have no idea what the sequence is in Outer Mongolia. In th UK, lights on the opposite road used to change at the same...
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