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Analogue Dub Siren

Discussion in 'General Electronics Chat' started by Rorut, Sep 27, 2016.

  1. Rorut

    Rorut Member

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    Could not be more thankful!
    I also bought the opa2134 .
    Will be fun to compare them
     
  2. spec

    spec Well-Known Member Most Helpful Member

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    No probs Rorut- bit of therapy for me.

    If you have a HiFi signal the OPA2134 will sound excellent.:cool:

    spec
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    A hifi siren sound??
     
  4. dave

    Dave New Member

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  5. Rorut

    Rorut Member

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    Im using that opa2134 for the music coming from the dj mixer to the delay. Sirens can stay with the Lm358 that you said would do the job :)
     
  6. Rorut

    Rorut Member

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    Wired it up but nothing happens just a huuummm :) anything I can measure to se whats wrong?
     

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  7. spec

    spec Well-Known Member Most Helpful Member

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    Oh dear. I hope the opamps are not oscillating. C1 (100nF) should be mounted as close as possible to the supply pins on the chip, with as short leads as possible, to provide good supply line decoupling. One dodge is to place the decoupling capacitor across the top of the chip and solder the leads to the top of the chip pins.

    What supply voltage are you using?

    Turn the 100K potentiometers to minimum (voltage gain of 1)

    Measure the supply voltage and 0V actually on the pins of the chip

    Measure the voltage at the junction of two pairs of 220K resistors: should be half the supply voltage.

    All inputs and outputs of the opamps should at the same voltage as the respective junctions of the 220K resistors.

    Good luck

    spec

    (PS hate to say this but the breadboard layout may be a problem)
     
    Last edited: Jan 5, 2017
  8. Rorut

    Rorut Member

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    thanks spec! :)
    I get a amplified sound on the lower channel of the circuit.
    gain pot does not do much but level do

    supply voltage 12v

    pin1: 10.8v
    pin2: 10.8v
    pin3: 11.9v
    pin4: 0
    pin5: 5.9v
    pin6: 5.9v
    pin7: 5.9v
    pin8: 12v

    :facepalm:
     
  9. spec

    spec Well-Known Member Most Helpful Member

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    Pins 1, 2 & 3 are incorrect. looks like there is a problem with the voltage at the junction of the two 220K resistors...wrong value?

    spec
     
  10. Rorut

    Rorut Member

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    Happy to know where the problem is :) Explains why only one channel is working. Resistor values are correct. I probably connected the resistors wrong.
    Need some sleep and will give it a second try tomorrow. And practice a bit more on breadboard layout :D
    Thank you very much!
     
    Last edited: Jan 5, 2017
  11. spec

    spec Well-Known Member Most Helpful Member

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    No probs Rorut- have a good sleep and all will fall into place tomorrow.:)

    Are you testing with an LM358? An LM358 would be best to get the circuit going.

    Do not worry about hum at this stage. It would be very surprising if there was no hum.:D

    Just to give you a clue, an opamp has a typical low frequency voltage gain of one million which means that just one microvolt at one of the input pins will result in a volt out. You can induce one microvolt on to an opamp pin by just looking at it.:arghh:

    spec
     
    Last edited: Jan 5, 2017
  12. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The messy wires and rows of contacts on a solderless breadboard are antennas that pickup mains hum that is all around you. The contacts might be intermittent.
     
    • Agree Agree x 1
  13. Rorut

    Rorut Member

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    I found the problem at first sight today :). Had the both pins of a 220k resistor connected to IC pin3. Now I get sound on both channels. No hum at all, (2.2uF removed some little hum) Moved that 100nF closer to pin 8.

    But... How impressed should I be? Gain control does barely do nothing. Level control can adjust sound to zero and to max. Everything at max gives not very much amplification. Almost the same as the first circuit "inverted" I posted.
    Why is gain doing almost nothing, maybe I connected something else wrong?
    Im working with the cheaper LM358

    Happy I got sound :)
     
    Last edited: Jan 6, 2017
  14. spec

    spec Well-Known Member Most Helpful Member

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    Ha Ha, good news.

    The amplifiers should produce a voltage gain of x 1 (with gain potentiometer set to zero Ohms) and x 100 (with gain set potentiometer set to 100K) I suspect the gain set potentiometers (PR1) are 1K instead of 100K or the 1K fixed resistors (R3) are 100K.

    spec
     
    Last edited: Jan 6, 2017
  15. Rorut

    Rorut Member

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    Yes :)
    Measured pots are 100K and resistors are 1K. So values are correct. Wierd... any other ideas?
    :)
     
    Last edited: Jan 6, 2017
  16. spec

    spec Well-Known Member Most Helpful Member

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    Are the lower ends of the 1K resistors connected to 0V via the 4.7uF capacitors?

    Are the 4.7uF capacitors the correct value?

    Are the 4.7uf capacitors the correct way around?

    What is the voltage on the positive connection of the 4.7uF capacitors (should be around 5.9V)?

    22uF, or higher, capacitors in place of the 4.7uF capacitors would be more suitable: lower frequency response (but not connected with the fault)

    spec
     
    Last edited: Jan 6, 2017
  17. Rorut

    Rorut Member

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    Yes to all.
    Voltage on 4.7uF is 6.5v, changed to 33uF but no luck. (Maybe sound quality got better with te 33uF. but not sure about that one) :)
    When i use the 100K trim pot. Nothing happens to volume. Tone of the sound only changes slightly...
    It is like it is bending the tone in some frequencies on the gain pot

    pin1: 5.2v
    pin2: 5.2v
    pin3: 5.9v
    pin4: 0
    pin5: 5.9v
    pin6: 5.8v
    pin7: 5.8v
    pin8: 12v
     
    Last edited: Jan 6, 2017
  18. spec

    spec Well-Known Member Most Helpful Member

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    Voltage on 4.7uF is 6.5v This is wrong- should be the same as pin 1 & 2 or pin 5 & 6

    pin1: 5.2v
    pin2: 5.2v
    pin3: 5.9v This is odd should be same as pin 1 & 2
    pin4: 0
    pin5: 5.9v
    pin6: 5.8v
    pin7: 5.8v
    pin8: 12v

    What meter are you using. Is it a digital multimeter. Can you establish what the input resistance is from the manual: sshould be around 10M Ohms.

    It looks as though the opamps are oscillating, but not sure.

    spec
     
  19. Rorut

    Rorut Member

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    When disconnecting the siren that shares the same power source I get.
    pin1: 6.06v
    pin2: 6.06v
    pin3: 5.99v
    pin4: 0
    pin5:5.98v
    pin6: 6.06v
    pin7: 6.06v
    pin8: 12v

    Using a UNI-T 139C multimeter
     
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Of course it is oscillating. It is built on a solderless breadboard.
     
  21. spec

    spec Well-Known Member Most Helpful Member

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    Thanks. That is all good.:cool:

    I will have a think.

    spec
     

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