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  1. C

    Relay pulse time - milliseconds

    Maybe a relay to isolate the wiring.
  2. C

    1.2w/10mA LEDs

    100 pcs 5mm Round white Superbright LED Light 20,000MCD $3.00 for 100 LEDs It didn't take Einstein to find the LEDs.
  3. C

    full size animatronic Dinosaur sound board help

    "You're welcome to come and have a play with my dinosaur " Is that some form of euphemism, I'm not aware of. . . .
  4. C

    1.2w/10mA LEDs

    "Would these little guys from Maplin do the trick ? " No, they are absolute rubbish. As all Maplin stuff is. I buy 20,000mcd by the thousand for 3 cents each.
  5. C

    Transistor hfe

    If you are only dissipating 70 watts per transistor, it does not matter which transistor you use.
  6. C

    Transistor hfe

    I told you before that there is ABSOLUTELY no difference between the two transistors. The losses will be exactly the same. That's why very few people understand electronics. You cannot learn it from a book. It is a waste of money to buy the other transistors. Thy are not a ballast resistor. A...
  7. C

    Transistor hfe

    "but the TIP2955 has a gain of 20@4A .."No between 20 and 70.
  8. C

    Transistor hfe

    Divide the output current by the current passing into the 7812 and you have the gain of the transistor.
  9. C

    Transistor hfe

    To start with, you have got no heat-sinking on the diodes. The PC track-work is absolutely essential to assist in keeping the diodes cool.
  10. C

    Transistor hfe

    What transistors are you using?
  11. C

    Transistor hfe

    A charged car battery is actually 12.6v
  12. C

    Transistor hfe

    The article also says: "I have heard from one reader whose output jumped to 35 Volt, not the regulated 12 Volts. This was caused by a short circuited power transistor. Should a short in any of the output transistors, occur, all 6 need to be un-soldered. Check with a multimeter set to resistance...
  13. C

    Transistor hfe

    The original article says: "The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. " IF YOU HAVE A 12v BATTERY - WHY DO YOU NEED THIS CIRCUIT ???????
  14. C

    Transistor hfe

    As far as you are concerned, both transistors dissipate EXACTLY the same wattage. Th only difference is the exact locations in the transistor and on the circuit, where the losses take place.
  15. C

    Transistor hfe

    As far as you are concerned, the losses produced by the transistors will be ABSOLUTELY IDENTICAL. The only difference is the base current for the MJ will be 1% of the TIP.
  16. C

    Transistor hfe

    You would be pushing the regulator to its maximum with the TIP and 30 amps. "And as its a more powerful transistor could it handle current more efficiently over the TIP2955 transistors specifications " No - the same. However the drive current for the TIP would be much higher.
  17. C

    Transistor hfe

    At the end of the day, both transistors will dissipate EXACTLY the same wattage. The only difference will be the regulator will dissipate 12 watts or more and about 1 watt.
  18. C

    Transistor hfe

    It depends on what we call the REGULATION OF THE TRANSFORMER. Normally, a 24v , 30 amp transformer will produce 27v AC on NO LOAD and 24v AC when fully loaded. 24v AC will convert to 33v6 , minus about 4v after it passes through the bridge. This means you could have 30v before the...
  19. C

    Transistor hfe

    I made a mistake with my reasoning above as I normally use 2N3055 transistors for the pass transistor. But when you are getting up into the high currents, you are much better off buying a switch-mode design. The losses in a linear circuit are 20% and everything has to have enormous heat-sinks...
  20. C

    Transistor hfe

    The original would never work. The base current needed to deliver 30 amps would need to be about 1 amp. 1 amp flowing through 100 ohm resistor would drop 100 volts. So the circuit is one of those junk designs that has never been tested. You transistor is a Darlington and will need less...
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