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  1. Hero999

    Ac to AC converter - help needed

    Why does it need to be AC? It's a heater so it doesn't make any difference whether it's AC or DC, just use a standard off the shelf 120VDC power supply and run the heater off it. A more crude solution is to use a 120VAC transformer with two primaryies designed to take 133V and connect them in...
  2. Hero999

    help to make this..

    A single AA battery has too lower voltage to light an LED, you need to use a Joule thief to increase the voltage enough to light it. Do you want the LED to remain on once the wood has been struck?
  3. Hero999

    Infrared cordless Headphone Amplifier help please

    The only receiver circuit I could find uses the obsolete MC3237. The transmitter is on a separate site, I don't know if it works on the same frequency, I haven't done any calculations.
  4. Hero999

    Amplifier For 600 kHz Signal

    Then you don't need a linear amplifier but a half-bridge or h-bridge as it's just a squarewave. You don't need PWM because the duty cycle doesn't vary. Does your signal generator have an inverted output? It would make it easier to do.
  5. Hero999

    Rechargeable Fan - Paintball Mask

    A battery will charge when it's connected to a higher voltage than the battery terminals and discharge when it's connected to a lower voltage. I would've thought the USB current limit would have been exceeded causing the USB to shut down so maybe the battery discharged into the USB port?
  6. Hero999

    Which bench power supply do you use?

    I bult my own using an LM317, a bridge rectifier, a mains transformer, and a few capacitors and resistors.
  7. Hero999

    Amplifier For 600 kHz Signal

    You don't need an amplifier, a simple MOSFET will do. You haven't given enought information.
  8. Hero999

    Transformer

    You're right, it's a waste of power because a 150kVA transformer will have more losses than a 7kVA transformer. However, the transformer doesn't generate any power, it just converts it from one voltage/current to another. A 150kVA transformer with no load connected to it will supply 0VA and it...
  9. Hero999

    Transformer

    Why would there be any danger? Think about it.
  10. Hero999

    LED driver

    I thought you said they were 30mA? What voltage is the adaptor? Here's a site which explains the difference between series and parallel LED circuits. http://www.ngineering.com/led_circuits.htm
  11. Hero999

    LED driver

    What voltage are the LEDs? What voltage is the adaptor? It's more efficient to connect them as strings of many in series, in parallel.
  12. Hero999

    [ARTICLE] Build your own UV exposure box

    Did you connect the foil to the earth/ground conductor? If not I suggest you do, otherwise it might become live if a fault develops.
  13. Hero999

    Design new 0 to 30V power supply.

    You could try that, I don't know what could be going wrong, it sounds like one of the op-amps is latching up.
  14. Hero999

    hi friends!!

    Hi, I don't have any frnds, whatever they are, but I have a couple of friends. :rolleyes:
  15. Hero999

    Design new 0 to 30V power supply.

    PictMaster, That does seem odd that the voltage shot up so high when the current limit was increased. Did it go back down to 12V or did it stay at 22V? roughrider, Tha't's not what I intended, although it will work. The zener was never intented to be a regulated voltage source, it's just...
  16. Hero999

    White led

    The resistor needs to be rated for at least 5W and don't leave it connected for very long - the power dissipation will be 0.352*100 = 12.25W which is much higher than the maximum rating but will be fine, as long as it's only connected for a few seconds and a large heatsink is used.
  17. Hero999

    DC/DC Converter (the proper diode)

    No. A DC-DC converter is a switched mode power supply which switches at a high frequency so a fast switching diode is required. That's true, you shouldn't puch components to their maximum ratings and with diodes you have the advantage of a lower voltage loss at currents much less than the...
  18. Hero999

    White led

    It depends on whether it can withstand a short circuit or not. Please post a schematic. An easy way is to connect a 100R power resistor and measure the voltage, it should be 35V. You might be able to get away with a 10R resistor or even just measuring the current with a meter but it depends...
  19. Hero999

    Understanding Safe Operating Area

    No, The graph show how much current the MOSFET can pass when it is not quite fully switched on. If it was switched off then no current would be flowing. The graph has nothing to do with switching and is about the saturation region when the MOSFET is neither fully on nor fully off and is...
  20. Hero999

    JFET Mic Pre Advise Please

    I don't see why it needs to be balanced. AC coupling is normally used to block the DC as you correctly suggested. A transformer will just ruin it, as mentioned above. Ballancing is normally done usign a differential amplifier which would need a matched pair of FETs in this case as you don't...
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