Thursday, March 1, 2012

Speaker protection with uPC1237

I was using IC uPC1237 for speaker protection in almost all my power amplifiers, because schematic is very easy to build with few external components.



Here is the latest version of the schematic that I use:

A transistor and LED were added to indicate when speakers are switched off.
The whole part with R1, R2, R3, R4, Q1 and J1 is optional and protection module will work without them.

The C1 value may be increased if there is false activation with high output signal level from amplifier. It is also preferable if C1 is non polar (bipolar), but these are harder to find, so if it is a polar, then put one with higher voltage - at least 50V
With these values of elements schematic will work with 24VAC, 32VDC, and will activate when there is more than ± 2VDC in output signal. Initial mute time will be around 3-4 seconds.
There are formulas in the schematic to calculate the values of the resistors for different supply voltages.

Bellow is a diagram how to connect speaker protection module with an amplifier.




A little older version of the protection module.


Here is a link for downloading an archive with PDF files of the project: DC Protection.rar
Use it on your responsibility.

UPDATE: 29.01.2019
The link for the project files is fixed and the archive include the latest version of PCB + Gerber files.
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18 comments:

  1. Solder DonSeptember 11, 2012 at 11:02 PM

    Good job!

    ReplyDelete
  2. ХристоNovember 15, 2013 at 1:45 PM

    Виж на страница "About".

    ReplyDelete
  3. UnknownDecember 31, 2013 at 12:34 AM

    This comment has been removed by the author.

    ReplyDelete
  4. ХристоFebruary 25, 2014 at 1:54 AM

    Благодаря!

    ReplyDelete
  5. UnknownMarch 10, 2014 at 7:06 AM

    I haven't tried it yet çause I need the parts list.
    Can you please post them.

    Thanks much

    ReplyDelete
  6. Ivan LukicDecember 25, 2016 at 11:02 AM

    This is the best PCB for uPC1237 that I found on the net. It's compact and I like the way that the relay arcs to ground instead to the speaker. I built it with the same relays (RAS 1215) and it functions perfectly.

    Regards

    Ivan Lukic
    Serbia

    ReplyDelete
  7. Ivan LukicDecember 17, 2017 at 6:28 PM

    Turn on delay and Loss of AC detection at the turn off works perfect but when I connect 9V battery to the output of amplifier protection does not disconnect the loudspeaker. I don't see any error on the PCB or schematic. How can I test if DC offset protection works properly? On my other protections when I connect 9V battery protections immediately disconnect output relay.

    ReplyDelete
    Replies
    1. UnknownOctober 29, 2018 at 3:54 PM

      You should test with DC voltage at the input of the protection circuit not at the output.

      Delete
    2. Lucky manMay 6, 2022 at 5:11 AM

      https://youtu.be/9Yb_KqMFOHA

      Delete
  8. MitkoNovember 15, 2018 at 10:35 PM

    File link for download is not valid, please re-upload again DC Protection.rar

    ReplyDelete
  9. warwinDecember 8, 2018 at 1:59 PM

    file invalid. please update the download link

    ReplyDelete
  10. cakyolOctober 30, 2020 at 11:20 PM

    - What should the value of C1 be to avoid false triggering on signals which are of very low frequencies, say around 15 - 18 Hz or so ?

    - To increase the start up delay to around 8-10 seconds, should R7 be increased to about 200 - 250 k ohms ?

    - Should pin1 be grounded (it is floating in the schematic) ?

    Thanks

    ReplyDelete
    Replies
    1. ХристоNovember 6, 2020 at 3:58 PM

      - I am not sure about C1. 47uF seems to work so far, but I have not tested it specifically with such low frequencies.
      - The mute delay can be extended with increasing R7 or C4 or both. In the datasheet there is a formula for calculating this delay.
      - It is not clear how to treat the pin 1. In the datasheet it stated that the threshold voltage is 0.67 V and that it need external circuit for overload detection. I haven't seen any problem with it dangling unconnected, but maybe it should be grounded (haven't tested it that way).
      Here the link to full datasheet: https://datasheetspdf.com/pdf-file/367818/NEC/UPC1237/1

      Delete
  11. cakyolOctober 31, 2020 at 6:44 AM

    Do you have the PCBs for sale for the speaker protection project ?
    Thanks

    ReplyDelete
    Replies
    1. ХристоNovember 6, 2020 at 4:01 PM

      I have not for the moment. Maybe I should make some assembled modules, but I am not sure they will sell - you can't compete with Chinese these days :(

      Delete
  12. David EisanDecember 26, 2020 at 10:20 PM

    Have you thought of doing a Mono version for dual mono amplifiers?

    ReplyDelete
  13. gatrehSeptember 21, 2021 at 7:46 AM

    Thank you for sharing..
    Could you please upload the non-smd Pcb too?

    ReplyDelete

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