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  1. duke37

    high amp 12v Power Supply

    I wouln't use a welding transformer since they are made with a high leakage inductance, normally adjusted with a wheel at the end. The inductance drops the voltage as the current rises, and more seriously, gives a voltage spike when the current is reduced. The rating of a welding transformer...
  2. duke37

    resistor should be renamed lol

    Hi CJ, A most interesting post, but you have several things wrong. 1. Nothing travels at the speed of light except light. I used to use an elecron microscope which accelerated the electrons with 100kV, they never got near the speed of light. Electrons in a solid travel very slowly indeed. 2...
  3. duke37

    What are the main components in electronic engineering?

    You will need to contact the manufacturers, they may get the sand from the local builder's merchant.
  4. duke37

    What are the main components in electronic engineering?

    Many elements are used in the electronics industry Copper for conductors. Aluminium for conductors, cases and capacitors. Tantalum for capacitors, wars are being waged over this (cotan). Iron/silicon for transformers, magnetic components and construction. Rare earth elements for magnets...
  5. duke37

    LED problem

    I did not study the diagram too closely, just that the 'arrers' should point to the negative . I have now looked up the BC327 (Q3 and Q2) and they are pnp which is correct. You have drawn Q3 as an npn. A npn transistor has the collector to the positive. A pnp transistor has the collector to...
  6. duke37

    Small washer pump timer?

    I'm back again! After a bit of thinking (hard work) I may have a simpler circuit. There will be three unused gates in the 4093 which will need to be tied down. The diodes could be 1N400x. The 4093 will of course need a ground and power (12V) connection.
  7. duke37

    LED problem

    The 4017 is a Johnson ring counter with one output out of ten active at any time, so the leds light up in sequence. I do not think that your modified circuit will work. 1. You have too many leds in the string for 12V, better to go for four or perhaps five. 2. Your current source is wrong...
  8. duke37

    Small washer pump timer?

    Here is my idea of what you can do. The first circuit is a simple current amplifier, use two transistors in a Darlington configuration or a Darlington transistor. This uses a relay to which switches when the voltage rises to a critical level The second circuit uses a 555 as a comparator and...
  9. duke37

    AC to transistor in tuner circuit

    You will never get narrow enough filters for this. Electronic organs used to use a crystal controlled oscillator running at about 1MHz and then divide this down for the various notes. You could do the same and then compare the note you have with the accurate generated note.
  10. duke37

    i need help for my a level project

    A magnet in each piece could activate a reed relay. With shiny bases, a led and sensor could be used.
  11. duke37

    LED problem

    If you use 12V you can put 4 leds in each string with appropriate resistors. In your first circuit, changing to fet drivers would allow 200 strings for each fet with no heat sinks. In the second circuit you can increase the current using transistor amplifiers (junction or fet).
  12. duke37

    Small washer pump timer?

    If you use your timer to initiate the action, then things become simple. I would use a capacitor charged through a resistor so that the voltage rises slowly. The motor would be connected to the 12V through the normally closed contacts of a relay so that the motor would come on as soon as the...
  13. duke37

    Small washer pump timer?

    To summarise 1. You want to turn on your pump every 15000 sec or so, timing not critical. 2. The pump needs to be activated for ? seconds. Please define. 3. The pump should be activated when the power is first applied. 4. You have 110V AC 60Hz and 12V 1.5A power. I would use CMOS which...
  14. duke37

    Smart hearing aid circuit that doens't work

    The op amp driving the audio amp is connected directly to the base of the transistor. This destroys any action of the biasing resistors. Add in a capacitor and check the transistor is OK.
  15. duke37

    ****ing speakers, how do they work

    I looked up the TRK-P6E and it is a radio/cassette player which can run on batteries. The output power will therefore be quite low. If you want more sound out, you will need more power. If you want a wider frequency range, you will need bigger speakers. If you want better stereo, you will...
  16. duke37

    Summing difference amp outputs

    Yes. you could connect both inputs to one op amp with a common offset, isn't it what audio mixers do, the problem would be of setting it up and you will do better to stick with what you have designed and understand.
  17. duke37

    Summing difference amp outputs

    Good diagram, well laid out and easy to read. R2 and R4 are the feedback resistors across their respective amps so that the amp output impedance will be low and not affected by the other amp. The load on the amp, say 50K is quite high and will not affect the output voltage at either amp...
  18. duke37

    Summing difference amp outputs

    I would think that your idea would work. The feedback with an op-amp enables the output voltage to be set more or less independent of the load. Why not post a sketch of what you have?
  19. duke37

    LED driver - improper crossover filter?

    1. I had never heard of Greinacher so I had a Wiki and found the correct spelling. 2. If you have two op-amps, I would not run them in parallel, they may fight against each other. A better solution would be to put your filters in front of the amps and use one for the high frequencies and the...
  20. duke37

    LED driver - improper crossover filter?

    1. I see that you have changed the input components. According to my calculations, the reactance of the capacitor will equal the resistor at a frequency of 1.6kHz so will act as a high pass filter. 2. Heinrich had only one R in his surname. 3. The forward voltage across the leds is a...
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