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Noob? Electronic car horn for bicycle

Discussion in 'General Electronics Discussion' started by PD64, May 12, 2017.

  1. PD64

    PD64

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    May 12, 2017
    20170512_131952.jpg G'day, I'm looking at adapting this car horn project -
    http://www.redcircuits.com/Page161.htm - as a bicycle horn for road commuting.
    I want to include a momentary push button switch on the handlebar. Would I locate this between the + side of battery and C6? Or is there a better location? (Why do many projects omit where switches should be? Especially something like a horn?)
    Also I have a 4 or 8 ohm speaker with one neg terminal, two pos terminals. How do I connect for 8 ohm use? (Altronics C0612D, 4 watts max.)
    Thank you
     
    Last edited: May 12, 2017
  2. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    Between battery '+' and the circuit is fine.
    You need to connect neg. and one of the two pos. terminals to the outputs of IC3. Unfortunately the datasheet of the speaker doesn'T tell which of the 2 pos. terminals is for 4 Ω and which is for 8 Ω operation. Use a multimeter, measure between neg. and the two pos. terminals. The one with the lower resistance (not necessarily 4 Ω as this is the AC impedance) is the 4 Ω terminal.
     
  3. PD64

    PD64

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    May 12, 2017
    Thx. I had already tried that. Both + terminals 4.3 ohms. How do I wire to get 8/8.6 ohms. If I join the 2 +s reading is 2.5 ohms.
     
  4. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    What is the resistance '+1' vs. '+2'?
     
  5. BobK

    BobK

    7,645
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    Jan 5, 2010
    Most likely you use the two + terminals for eight Ohms.

    Bob
     
    Harald Kapp likes this.
  6. PD64

    PD64

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    May 12, 2017
    Both 4.3 ohms
     
  7. PD64

    PD64

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    May 12, 2017
    That gives 2.5ohms the way i connected. Is there a particular way to "add" the terminal values?
     
  8. PD64

    PD64

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    May 12, 2017
    I forgot to ask about what specs switch to use, thanks
     
  9. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    ??? What do you mean by both?
    What I meant was to measure resistance between the two + terminals.
    With respect to Bob's post #5 I'd expect twice the resistance between the 2 '+' terminals than between one '+' terminal and the '-' terminal.
     
  10. Audioguru

    Audioguru

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    Sep 24, 2016
    1) The TDA7052 is not available anymore in a thorough-holes package, instead it is available in a tiny surface-mount package that will overheat when powered from 6V or more when driving an 8 ohm speaker. The TDA7052AT in the tiny package is shown in its datasheet with fairly low output power with a 16 ohm speaker and a 6V battery. Use a more powerful modern amplifier IC from Texas Instruments.

    2) The poor quality speaker you selected is HUGE! It is 8" in diameter and it needs an enormous enclosure. Use a small horn speaker instead that already has a small case.
     
  11. PD64

    PD64

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    May 12, 2017
    Okay, now measured from +(photo left) to +(photo right), reading is 8 ohms. As a noob it didn't seem right to expect + to + connection. Do i wire as a speaker like this? Or is this just a test?
     
  12. PD64

    PD64

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    May 12, 2017
    1. Thx. I am a noob. What would be a suitable replacement ic with the same pinout so the existing circuit would work?
    2. The speaker i selected is only for test purpose, but 4" diam, not 8". I'm later going for a 50mm speaker.
     
  13. PD64

    PD64

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    May 12, 2017
    I assembled a very rough breadboard circuit with a lm386 amp. No output. I looked online at the pinouts of the lm386 vs tda7052, to a noob the purpose of the pinouts are completely different.
    1.If any of the other amps (lm386, tda2003, tda1516bq) are used does the circuit have to be redesigned? I note the last two amps appear completely different.
    2. I ordered tda7052a online awaiting delivery. Should this work?
    3.I looked at redcircuits cuckoo-song generator project. Even as a noob I think I noticed a mistake in the schematic. So my question is, should the car horn work as drawn?

    Thanks.
     
  14. davenn

    davenn Moderator

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    Sep 5, 2009
    Yes

    of course ..... the 2 amp chips are totally different

    yes

    well that is the originally used chip

    what mistake ?
     
  15. Audioguru

    Audioguru

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    Sep 24, 2016
    The TDA7052A is also not available anymore. The TDA7052AT is also not made anymore but some distributors still have some. It is tiny and will melt if the speaker is less than 16 ohms and if the supply is higher than 6V. It is different than the original TDA7052 because it has a built-in volume control (pin 4) that might need to be connected with a pot and capacitor as shown in the datasheet.

    If you ordered from ebay (China) then whatever they send you might be a fake.

    You are correct, the 1nF value for C4 on the original schematic is wrong because it will pass only very high frequency squeaking sounds. It should be at least 100nF or 220nF.
     
  16. PD64

    PD64

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    May 12, 2017
  17. Audioguru

    Audioguru

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    Sep 24, 2016
    A noob must learn to look at the manufacturer's website to see if a product is still being made. A noob must look at the datasheet of an IC replacement and compare it to the original part's datasheet. The datasheet tells you everything about it.

    Philips (now called NXP) invented the TDA7052 amplifier IC a long time ago and updated it with the "A", "B" and "AT" versions. The TDA7052 was discontinued in 2009 and the others a little later. I usually look at Digikey to see if they have anything. Here is what NXP says today:
     

    Attached Files:

    PD64 likes this.
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