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  1. Hero999

    Smallest possible LED stoplight circuit

    What sort of sequence do you wand? Red, yellow then green? Or: Red, red + yellow, green, yellow, green? I can think of a simple way of doing it using the LM339, the CD4017 will also work. The comparator idea has the advantage of using less active parts but needs more passives and is only...
  2. Hero999

    Milliamp Question

    Yes, the device will take as much current as it needs, research Ohm's law.
  3. Hero999

    Transmitting video on radio FM band

    Yes you do have to find another solutaion for your video transmitter. You're right, that you can alter the frequency of an FM transmitter by changing the value of the capacitor and inductor but when the frequency approaches the transistor's transition frequency you need a faster transistor.
  4. Hero999

    MOSFETS in parallel

    Why not? The 555 can work all the way up to 500kHz. 0.8A. Would using a push-pull emitter follower configuration be any better?
  5. Hero999

    Overload Protector A16 ???

    It's not very good is it? If you can get hold of the 2SA16 then good for you but if you can replace it with a cheaper equivalent then all the better.
  6. Hero999

    Overload Protector A16 ???

    The lack of a schematic was a greater barrier to getting help than your poor English. I couldn't find much information about 1A16 on the Internet. I imagine that any PNP transistor rated to 1.5A will do.
  7. Hero999

    MOSFETS in parallel

    Unfortunately, the turn on will be slower due to the 330R. I doubt there's a significant difference between driving it directly from the 555 and via the 2N2222A.
  8. Hero999

    Re: Ldi/dt of an inductor

    Unfortunately protection diodes can shorten the life of the relay because the current decays more slowly when it's turned off causing the contacts to open more slowly which increases arcing across the contacts. A resistor in series with the diode (about the same value as the coil resistance as a...
  9. Hero999

    Overload Protector A16 ???

    Yes, you'll nevery get any help until you give enough information. Yes, it will work although it's a very crude and inefficient solution, a switching regulator is better idea.
  10. Hero999

    Overload Protector A16 ???

    Yes, it's being used as a current limiter. The 2N2955 is a booster transistor, when the voltage across the 50R resistor (or is it 60R? the schematic is too fuzzy) exceeds about 0.7V it turns on, allowing current to bypass  the regulator. A16 is acting as a current limiter, when the across the...
  11. Hero999

    MOSFETS in parallel

    I don't see what the 2N2222A is adding to the circuit, if anything it's making it worse not better, I'd get rid of it and drive the MOSFET directly from the 555. MOSFETs can be paralleled but why not use a single better MOSFET such as the IRL540, rather than loads the obsolete IRF510.
  12. Hero999

    Re: 0-12 Volts LM317 PSU

    This will work, when the output voltage is set to under 12V the power is drawn from the centre tap cutting the power dissipated by U1. It's designed for a 15-0-15V transformer, for a 9-0-9V change the D2 to 6.2V.
  13. Hero999

    Overload Protector A16 ???

    It could be used as a switch, amplifier or (as you've said) part of a current limiting circuit. Bipolar transistors have so many applications that it's impossible to tell you what it's doing from what you've said. For example if I asked you "I've seen a flat head screw; what's it holding...
  14. Hero999

    0-30 Vdc Stabilized Power Supply

    Use the heaviest copper board you can and cover all high current carrying traces with a thick layer of solder.
  15. Hero999

    [b]Questions regarding Switched-Mode Power Supply[/b]

    In a SMPS, the output transistor is either on or off. In a linear power supply, the output transistor always operates in its linear region, hence the name linear power supply.
  16. Hero999

    Re: 0-12 Volts LM317 PSU

    This can be solved by using a centre tapped transformer and taking the power from the tap when the output voltage is set below a certain level. I'll post a schematic if you're interested.
  17. Hero999

    Re: 0-12 Volts LM317 PSU

    It does, for a start 1.5A is only guaranteed at (VIN-VOUT) ≤ 15V, see page 5. And there's a graph showing the safe area protection, see page 6. http://www.national.com/ds/LM/LM117.pdf
  18. Hero999

    Laptop battery life increaser - would this work?

    I've heard of this sort of thing before but never seen any real evidence. It's certainly true that laptop batteries have a limited number of charge and discharge cycles but the rating is in full cycles, not partial cycles. Discharging a battery to 95% capacity then recharging to 100% does not...
  19. Hero999

    Electro Magnetic Pulse

    A lot. Don't even try to do it, it's a very stupid, dangerous and illegal idea.
  20. Hero999

    running 12v ac device on 12v dc

    It probably also uses a voltage doubler circuit to generate both positive an negative voltages. Making an inverter to get 12VAC from 12VDC is possible but not simple. First you need to convert 12VDC to 17VDC, then use an h-bridge and oscillator to convert it to AC.
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