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  1. dorke

    Screamingly easy o-scope problem

    Well ,you have one right on your scope...
  2. dorke

    Screamingly easy o-scope problem

    That is totally expected: Both ch1 and ch2 are at "GND" position. move them to DC and adjust the volts/div to 5V;)
  3. dorke

    Portable USB phone Charger Design Help

    My 2 cents: Whatever you build don't hook it up to your LG phone. It will be a shame to destroy it... furthermore ,chargers done the wrong way ,can cause the battery to explode. So for your own good try some other project to learn.:eek:
  4. dorke

    Screamingly easy o-scope problem

    Here is your pic with things you need to change on it. This set-up of the scope should display both channels in non-store mode regardlessof what is connected to the inputs. Legend: red : put the scope knob in that position. blue : push- button not pressed. green : push- button pressed.
  5. dorke

    Rotary sensor with logic output, kind of...

    Garberg, Another important missing fact is ,what is causing the axle to rotate . From your "...mouse wheel", I guess it is a small thing. From: "It will either be rotating at maybe 100rpm or not at all" It may be a small D.C motor. If this is indeed the case,the easiest way would be: monitor...
  6. dorke

    Another transistor discussion

    Agree it doesn't, it only feels the pain... ;)
  7. dorke

    Another transistor discussion

    Ratch, Agree with you on all. but number 4)A BJT is a transconductance amplifier- that is true only in C.E ,but not in C.C or C.B.
  8. dorke

    Another transistor discussion

    That is true,Tr in reverse active mode. But : 1.It is kind of a "trick": reversing the rolls of collector and emitter. 2.It isn't the playground of beginners. 3. I have never used it,have you?
  9. dorke

    Another transistor discussion

    Well, The best I can say for it is being "partly true"...;) The only fully true statement is the current composition ie=ib+ic. Putting it in words : The emitter current is the sum of the base and collector currents. In the extreme case of large hfe, like in a darlington transistor(hfe=1000 or...
  10. dorke

    How do I figure out these resistors?

    heavans, How would a beginner learn if you try to "chew " it for him...? xgabrielx, If you want to learn, come back to this thread . there is much more on this issue...
  11. dorke

    QSC 850 help

    Well, E101 and E201 are both P1 GND(from the sch.) -they are the same point,no problem here that is the way it should be. Looks to me like they shouldn't be connected to chassis GND. Can you trace that on the boards? maybe post some good pictures of the boards?
  12. dorke

    What language is this Receiver Displaying?

    Rick , You can use the front panel to perform the self test of the FL,you don't need the remote for that. Here is how: 1.The specific test is selected from a menu structure which consist of a main menu with 11 entries(subjects) each entry has sub-menu entries. For the FL test you need...
  13. dorke

    Optoisolator

    Jeff, What is the current your Arduino Uno + every thing it drives requires?
  14. dorke

    Another transistor discussion

    A beginner is thinking like this : "same current flowing here" : My words are chosen to explicitly explain the composition of currents. You can contradict me any time you want. and, thanks for letting me know the meaning of Ib, what would I have done without you Kid...
  15. dorke

    QSC 850 help

    Disconnect both E200 and E201. Measure resistance between JP15 and JP16 to verify short is on the output board. Measure resistance between E200 and E201 as well. .
  16. dorke

    QSC 850 help

    Woody, Dave is correct ,the IC is NE5532 it is U101 and U201 in sockets. There is no U102 on the board and NE5532 is non-existent . What IC tester are you using ? From the SM:
  17. dorke

    12v to 5v

    Well you can easily measure it . Connect like you intended ( 5v, led,resistor). use a resistor =1k potentiometer in series with 100 ohm. Get the correct luminescence you need from the led -important start with the pot. at max value and lower the resistance! VF==> measure the voltage on the...
  18. dorke

    Use a ground pin as a switch

    1.In general ,when switching something we prefer to be as close as possible to an idle switch. that means: A.zero on resistance. B.Infinite off resistance. C.Minimum control current. D.zero switching time (not relevant here) All(A-C) are present in the Mosfet implementation , but non in the BTU...
  19. dorke

    Simple LED timer circuit

    Well not quite... The charging energy of the cap is negligible here is why: Each time you activate circuit consume energy from the battery to charge the Cap.+light the LED The simplest thing to compare is the charge(in Coulomb) drown from the battery: The charge in a fully charged cap is...
  20. dorke

    12v to 5v

    spike, If all you need is TO light a LED(s) you don't need to step-down the voltage! Connect the LED directly to 12V with a series resistor(just like you do with 5v). The resistor value will be different that is all. For the LED you used above with 220 Ohm Calculate R for 12V: R=220+7000/i ...
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