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  1. C

    What Potentiometer should I get to control the speed of a computer fan?

    For a start, the pot must be able to take 350mA without burning out. Next, you want to drop about 6v to 8v to reduce the speed. The effective resistance of the fan is about 38 ohms. If you add about 100R pot, the fan will reduce in speed. A 100R pot capable of handling 350mA is 12 watts. A...
  2. C

    4 state illumination controller

    Just use a CD 4017 IC
  3. C

    Adjustable Schmitt Trigger Circuit Help

    Or use a Schmitt Trigger made with transistors
  4. C

    Sensing circuit for line following robot

    I will make it simpler for you. Replace the IR diode with a 10k resistor. This means you have half rail on the + input. Now adjust the 10k pot and with a LED and 220R on the output you will see the LED come on.
  5. C

    Noise issue

    The hum is coming from your recording equipment because it is powered from a plug pack connected to the mains.
  6. C

    Pulse transformer

    "I couldn't disagree with you more!" Let me just inform you of the truth of the matter. Just because there has been 30 billion chips sold and thousands of circuits, don't mean it is not the worst chip ever designed. For a start, the mere fact that there has been a number of attempts to improve...
  7. C

    Pulse transformer

    It's a shit of a chip. The worst chip ever designed.
  8. C

    Pulse transformer

    It looks like the transformer is upsetting the frequency (waveform) produced by the 555. Try separating the two with a buffer transistor and separate power supplies. The transformer DC resistance is far too low for the 555.
  9. C

    Switch capacitor = low pass filter ?

    I don't understand the question, but a filter is a circuit that only allows a certain frequency or a range of frequencies to emerge from the circuit. A LOW PASS filter only allows the LOW FREQUENCIES to emerge. The simplest filter consists of a capacitor and a resistor. We know that if we...
  10. C

    Replacing a 9Vdc relay with a transistor switch

    Just connect in place of the original relay. If you can only get SPDT, use 2 x CMOS relays.
  11. C

    Replacing a 9Vdc relay with a transistor switch

    You can get a CMOS relay @1mA
  12. C

    Electronic supply, help.

    If you have the best invention in the world, build 10 of them and put them on eBay AT COST PRICE with free postage and see how they go. I had the best invention ever.I put them on eBay FOR FREE and go no replies.
  13. C

    Electronic supply, help.

    I was negotiating a cost for a piece of equipment to be developed with the Chinese and then I asked my Chinese friend to seek prices and he came back with prices that were 10%. I will never deal with the Chinese again. Even electronics magazines are dying and the same with component...
  14. C

    Electronic supply, help.

    "You haven't even seen my business plan." Look around you. How many shops sell electronics??? Look at Tandy Radio Shack THEY ARE ALL GONE. Sell hamburgers. Everyone needs to eat. No-one needs electronics.
  15. C

    Piezo-triggered twinkling LEDs

    You can already buy shoes that do that.
  16. C

    Replacing a 9Vdc relay with a transistor switch

    Do you want complete isolation for the sensor?
  17. C

    Sensing circuit for line following robot

    The first thing you do is put a 10k pot in place of the 10k and IR receiver and adjust the pot and let us know if the output immediately changes from LOW to HIGH.
  18. C

    Horizontal one line on my sharp tv

    The most likely problem is a dry joint. Wiggle the board.
  19. C

    Small Inductance meter

    There are many LCR testers and they come assembled for about $15 to $20. It will measure 1p and 2p and very small inductances (1uH) by a very clever trick.
  20. C

    Got room for a resistor? :D

    Work out the value of resistance . . . . .
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