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  1. Hero999

    direct current stimulation

    What's the maximum voltage? A constant current source can be easilly be made with an op-amp or even a couple of transistors.
  2. Hero999

    LED Necklace

    Yes, you can connect half the LEDs to one channel and half to the other channel but you'll need two transistors for that.
  3. Hero999

    LED Necklace

    You only need to use one channel, the 0V goes to 0V and the input can be connected to either the left or right channel. It's possible to use both channels but you'll need a resistor for each, for more information, look at the graphical drawing of the circuit I posted on Electrotech.
  4. Hero999

    LED Necklace

    1) Think about it. 2) Only you know that.
  5. Hero999

    max232 external capacitors

    It uses a circuit known as a charge pump to generate a higher voltage from the power supply. The capacitor values depend on many factors, here's an article which discusses how to calculate them...
  6. Hero999

    [ARTICLE] Build your own UV exposure box

    Yes, those will be fine.
  7. Hero999

    help

    Why are so many people starting pointless polls recently? I vote for both yes and no.
  8. Hero999

    LED Necklace

    You can use any NPN transistor which can handle 300mA or more, e.g. BC338, PN2222A, 2N2369 etc.
  9. Hero999

    LED Necklace

    Yes, that's the idea.
  10. Hero999

    LED Necklace

    I designed a simple circuit that will do this and posted it over on Electrotech Online but don't expect any help from me over there because the idiot administrator banned me for disagreeing with him. If you want help, ask here or on SiliconTronics.com. Fortunately it can be found on the second...
  11. Hero999

    Filters

    I'm sure it's possible but you'll need some damping otherwise the bandwith will be very tiny.
  12. Hero999

    suggest naman :)) for THESIS project para sa computer engineering students.

    Speaking English might help. Also appreciate that no one here is going to do all of the work for you.
  13. Hero999

    Automatic Fan Controller - Help (w/ relay?) Please!

    This circuit demonstrates why the 741 is such a poor choice for this application. It sounds like Q1 isn't turning enough to activate the relay but it's t,urning on to keep the relay activated once you've cheated by activating the relay manually. The relay has hysteresis, the turn on voltage is...
  14. Hero999

    UPS designing. where to start?

    How long do you need it to last for? 2kW is 200A from a 12V battery, assuming 80% efficiency, consider using a higher voltage, for example 2kW is only 50A from a 48V battery.
  15. Hero999

    Power Supply for capacitor bank

    It depends on the circuit, look at the maximum voltage across the MOSFET.
  16. Hero999

    Power Supply for capacitor bank

    I thought you said it ran from 12V to 14V? Using a higher voltage rating is fine but you'll find that MOSFETs with a higher voltage rating will have a higher on resistance.
  17. Hero999

    ir2130

    You need at least 311V DC to get 220VAC. Using a square wave is bad for the motor.
  18. Hero999

    Power Supply for capacitor bank

    As far as controlling it from your PC is concerned a parallel port can be used with no MCU - it's fairly easy to set bits high and low. Unfortunately parallel ports aren't very common on new PCs so you'll need to use USB which requires an MCU but I can't help you with that. MOSFETs are better...
  19. Hero999

    UnFETtered Crystal Radio

    Have you tried using a diode with the transformer and ear bud? I see no reason why it shouldn't work. For more volume use a voltage doubler circuit.
  20. Hero999

    1.5V buzzer circuit

    I've just tested it today and it works quite well. It sounds similar to a piezo buzzer. It's quite loud considering it's only running off a single AA cell, though I don't have a sound meter so it's pretty subjective. I varied the supply voltage between 0.944V to 1.54V and the frequency drifted...
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