boosting output of oscillator

Discussion in 'General Electronics Chat' started by 3dchipmaker, Jul 15, 2006.

  1. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
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    i would like to know how to boost output voltage of an oscillator and still maintain 30 pulses per second.using a 12 v stage or if someone knows a better schematic than 555 timer
     
  2. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
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    Show the schematic you have, it's hard to guess what you need without it.
     
  3. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
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    attached is schematic

    thanks,
    3d
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    The circuit you've shown will provide 12v pulses. What voltage level of pulses are needed?
     
  5. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
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    Thanks For Your Reply.
    The Problem Is That When Assembled The Out Put Is 6v I Would Like It To Be As Close To 12v As Possible And Still Maintain Pulse Rate.
     
  6. hgmjr

    Moderator

    Jan 28, 2005
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    When you measure the output of the circuit to be 6v, do you have the output connected to anything other than a meter or an oscilloscope?

    The reason for my question is that maybe your load is causing your reading to be low. Keep in mind that the output impedance of the driver shown in your attached schematic is 100 ohms. There is also an LED in series with the output. If you are measuring your 6v signal across whatever load you are connected to, then if the load is around 180 ohms or so then the output voltage across the load would be pretty close to 6v.

    hgmjr
     
  7. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
    0
    Thanks For Your Reply,

    Voltage Going Into Collector On Transistor Is 12v. Voltage On Base Is 6v. But Emitter Voltage Is 6v Before Resistor And Led. Is There Any Way To Ramp Up Voltage As Close To 12v Rail As Possible
    At Emitter Discharge Without Changing Frequency
     
  8. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
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    can this be done? ask's the electronicly challenged.all help will be greatly appreciated.

    thanks,
    3d
     
  9. hgmjr

    Moderator

    Jan 28, 2005
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    The circuit as shown in your schematic should produce a signal swing at the emitter of transistor between 0V and 11.3V without any problem.

    Is it possible that you have accidentally installed the transistor so that the emitter and the collector have been swapped? This could cause your problem. To check that the 555 output is swinging between 0V and 12V, you can temporarily disconnect the 555 from the transistor and check the output at pin 3 of the 555 without any load. If the 555 is swinging between 0V and 12V then the problem most likely resides in the way the transistor is connected up.

    hgmjr
     
  10. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
    0
    thanks for your help!!
    i have another schematic that puts out about what i want and has a good sharp pulse.i need to tune the pulse rate. it is in the ballpark but i want 30 pulses per second. can i attach a pot to this circuit to control pulserate and if so where?
     
  11. pebe

    AAC Fanatic!

    Oct 11, 2004
    628
    3
    If you are using the standard bipolar 555, its output is fed from the 12v rail via two NPN transistors connected as a Darlington pair. That, together with your external transistor, gives 3 x 0.7v drops from the rail. So your output cannot exceed 9.9V even with a high value resistive load.
     
  12. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
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    thanks for your reply!

    what i cant understand is why the output voltage is 6v. i guess that is how circuit is designed because they are feeding base of transistor whith the output at pin 3
     
  13. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Have you disconnected the transistor and made the measurement that hgmjr suggested?
     
  14. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
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    thanks for your reply!

    yes i removed transistor and voltage was 6v and thats what runs base on transistor pin 3 on 555. i tried everything i could think of before this forum.
    swapping testing disconnecting reconnecting for 3 weeks.i just know the basics of electronics i guess what i really need is a bare bones oscillating circuit that i can get as close to 12v output and pulse 30 times a second with 12v input.does anyone know of a schematic?

    thanks for all of your help!
    3d
     
  15. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    What is the condition of the power source? Is that 12 Volt battery drained to 6 Volts?
     
  16. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
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    thanks for reply,
    im using a variable dc power supply and its putting out 12vdc i tested with multimeter.attached is assembly i assembled exactly like assembly shows i built 4 of these and everyone works the same with the same output levels maybe its a problem with assmbly can you check and see if assembly is correct to schematic it looked like to me but i just know basics

    thanks,
    3d
     
  17. hgmjr

    Moderator

    Jan 28, 2005
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    I think you need to connect pin 7 of your 555 to the junction of the pot and the feedback resistor R2.

    http://www.allaboutcircuits.com/vol_6/chpt_6/7.html is a link to an astable 555 oscillator in the AAC tutorial section that shows how the discharge pin should be connected.

    Without pin 7 (discharge) connected up, the 555 will not oscillate properly since there is nothing to discharge the capacitor to start the charge cycle over.

    Your schematic seems not to show pin 7 being connected at all.

    hgmjr
     
  18. 3dchipmaker

    Thread Starter Member

    Jul 15, 2006
    23
    0
    thanks again,
    i will try
     
  19. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    3D,

    Where did you get that original schematic in your first posting? It also doesn't show pin 7 connected.
     
  20. pebe

    AAC Fanatic!

    Oct 11, 2004
    628
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    The original circuit shown for the 555 will work OK. It does not need the discharge pin connected. It is an astable oscillator with a unity mark-space ratio. The problem, as I said before, is that the output will not go to the +ve rail.

    Wiring the driver transistor as in the attached circuit will ensure that the transistor is switched hard on and off and the output will swing between about 0.3V and 12V. The fact that the transistor inverts the signal doesn't matter.
     
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