Noise in speaker when 2 arduinos connected via Serial pins

[FE3DS]

Hi, very good project!
I use your synth with arduino Pro-mini 5V/16MHz and keypad to generate DTMF tones.
My Pro-Mini is connected to a MEGA2560 via Serial port.
But I have a problem:
If MEGA and Pro-Mini powered by their own power supply and connected each other via GND/TX/RX pins -> OK
If MEGA and Pro-Mini powered by the same power supply and connected each other via 5V/GND/TX/RX pins -> no OK. I have a noise in speaker.
How can I resolve that?
Thanks in advance.

[dzlonline]

Hi. Sounds like a ground-loop/power supply problem. Try connecting all ground wires at one central point near the power supply. Try adding a large capacitor ~1000µF between this ground point and the 5Vsupply (also all connected in one point). You may try to pass all serial signals via. 100R resistors to limit RF noise and fast currents. The speakers (if connected directly to the chip) can draw around 100mA AC current at 32KHz this is likely transmitted via. the 5V line. Let me know how it goes... Cheers Dzl

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On Tue, Sep 28, 2021 at 10:50 AM FE3DS ***@***.***> wrote: Hi, very good project! I use your synth with arduino Pro-mini 5V/16MHz and keypad to generate DTMF tones. My Pro-Mini is connected to a MEGA2560 via Serial port. But I have a problem: If MEGA and Pro-Mini powered by their own power supply and connected each other via GND/TX/RX pins -> OK If MEGA and Pro-Mini powered by the same power supply and connected each other via 5V/GND/TX/RX pins -> no OK. I have a noise in speaker. How can I resolve that? Thanks in advance. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#24>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA7XCSDTWR62HDWZSKMTX2TUEF6VLANCNFSM5E43VJ6Q> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[FE3DS]

Hi, Thanks for these informations. I will purchase this capacitor and test that. Thanks a lot. Bien cordialement, Nicolas BOULAY. FE3DS. www.fe3ds.fr<http://www.fe3ds.fr/> -- www.facebook.com/FE3DS<http://www.facebook.com/FE3DS> Le 28 sept. 2021 à 11:48, Dzl ***@***.***> a écrit :  Hi. Sounds like a ground-loop/power supply problem. Try connecting all ground wires at one central point near the power supply. Try adding a large capacitor ~1000µF between this ground point and the 5Vsupply (also all connected in one point). You may try to pass all serial signals via. 100R resistors to limit RF noise and fast currents. The speakers (if connected directly to the chip) can draw around 100mA AC current at 32KHz this is likely transmitted via. the 5V line. Let me know how it goes... Cheers Dzl

On Tue, Sep 28, 2021 at 10:50 AM FE3DS ***@***.***> wrote: Hi, very good project! I use your synth with arduino Pro-mini 5V/16MHz and keypad to generate DTMF tones. My Pro-Mini is connected to a MEGA2560 via Serial port. But I have a problem: If MEGA and Pro-Mini powered by their own power supply and connected each other via GND/TX/RX pins -> OK If MEGA and Pro-Mini powered by the same power supply and connected each other via 5V/GND/TX/RX pins -> no OK. I have a noise in speaker. How can I resolve that? Thanks in advance. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#24>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA7XCSDTWR62HDWZSKMTX2TUEF6VLANCNFSM5E43VJ6Q> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

— You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub<#24 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AR67PKWZ7HJ6RCQ3J47BJDLUEGFPHANCNFSM5E43VJ6Q>. Triage notifications on the go with GitHub Mobile for iOS<https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android<https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[dzlonline]

For testing you can also just run one of the Arduinos from a power bank and _not_ connect 5V between the boards. This should have the same effect.

…

On Tue, Sep 28, 2021, 16:57 FE3DS ***@***.***> wrote: Hi, Thanks for these informations. I will purchase this capacitor and test that. Thanks a lot. Bien cordialement, Nicolas BOULAY. FE3DS. www.fe3ds.fr<http://www.fe3ds.fr/> -- www.facebook.com/FE3DS< http://www.facebook.com/FE3DS> Le 28 sept. 2021 à 11:48, Dzl ***@***.***> a écrit :  Hi. Sounds like a ground-loop/power supply problem. Try connecting all ground wires at one central point near the power supply. Try adding a large capacitor ~1000µF between this ground point and the 5Vsupply (also all connected in one point). You may try to pass all serial signals via. 100R resistors to limit RF noise and fast currents. The speakers (if connected directly to the chip) can draw around 100mA AC current at 32KHz this is likely transmitted via. the 5V line. Let me know how it goes... Cheers Dzl On Tue, Sep 28, 2021 at 10:50 AM FE3DS ***@***.***> wrote: > Hi, very good project! > I use your synth with arduino Pro-mini 5V/16MHz and keypad to generate > DTMF tones. > My Pro-Mini is connected to a MEGA2560 via Serial port. > But I have a problem: > If MEGA and Pro-Mini powered by their own power supply and connected each > other via GND/TX/RX pins -> OK > If MEGA and Pro-Mini powered by the same power supply and connected each > other via 5V/GND/TX/RX pins -> no OK. I have a noise in speaker. > How can I resolve that? > Thanks in advance. > > — > You are receiving this because you are subscribed to this thread. > Reply to this email directly, view it on GitHub > <#24>, or unsubscribe > < https://github.com/notifications/unsubscribe-auth/AA7XCSDTWR62HDWZSKMTX2TUEF6VLANCNFSM5E43VJ6Q> > . > Triage notifications on the go with GitHub Mobile for iOS > < https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> > or Android > < https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. > > — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub< #24 (comment)>, or unsubscribe< https://github.com/notifications/unsubscribe-auth/AR67PKWZ7HJ6RCQ3J47BJDLUEGFPHANCNFSM5E43VJ6Q>. Triage notifications on the go with GitHub Mobile for iOS< https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android< https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#24 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA7XCSDODUZPZQYEWYOMBMTUEHJUJANCNFSM5E43VJ6Q> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

[FE3DS]

Hi, I’ve Added 3 capacitors (1000µF each) in parrallel to get a 3000µF capacitor. It’s make the job. The noise is very little now. (you must have your head close the hp to ear the little noise) It’s good for me. Thanks for your help. Bien cordialement, Nicolas BOULAY. FE3DS. www.fe3ds.fr -- www.facebook.com/FE3DS De : ***@***.***> Envoyé le :mercredi 29 septembre 2021 13:25 À : ***@***.***> Cc : ***@***.***>; ***@***.***> Objet :Re: [dzlonline/the_synth] Noise in speaker when 2 arduinos connected via Serial pins (#24) For testing you can also just run one of the Arduinos from a power bank and _not_ connect 5V between the boards. This should have the same effect.

On Tue, Sep 28, 2021, 16:57 FE3DS ***@***.***> wrote: Hi, Thanks for these informations. I will purchase this capacitor and test that. Thanks a lot. Bien cordialement, Nicolas BOULAY. FE3DS. www.fe3ds.fr<http://www.fe3ds.fr/> -- www.facebook.com/FE3DS< http://www.facebook.com/FE3DS> Le 28 sept. 2021 à 11:48, Dzl ***@***.***> a écrit :  Hi. Sounds like a ground-loop/power supply problem. Try connecting all ground wires at one central point near the power supply. Try adding a large capacitor ~1000µF between this ground point and the 5Vsupply (also all connected in one point). You may try to pass all serial signals via. 100R resistors to limit RF noise and fast currents. The speakers (if connected directly to the chip) can draw around 100mA AC current at 32KHz this is likely transmitted via. the 5V line. Let me know how it goes... Cheers Dzl On Tue, Sep 28, 2021 at 10:50 AM FE3DS ***@***.***> wrote: > Hi, very good project! > I use your synth with arduino Pro-mini 5V/16MHz and keypad to generate > DTMF tones. > My Pro-Mini is connected to a MEGA2560 via Serial port. > But I have a problem: > If MEGA and Pro-Mini powered by their own power supply and connected each > other via GND/TX/RX pins -> OK > If MEGA and Pro-Mini powered by the same power supply and connected each > other via 5V/GND/TX/RX pins -> no OK. I have a noise in speaker. > How can I resolve that? > Thanks in advance. > > — > You are receiving this because you are subscribed to this thread. > Reply to this email directly, view it on GitHub > <#24>, or unsubscribe > < https://github.com/notifications/unsubscribe-auth/AA7XCSDTWR62HDWZSKMTX2TUEF6VLANCNFSM5E43VJ6Q> > . > Triage notifications on the go with GitHub Mobile for iOS > < https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> > or Android > < https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. > > — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub< #24 (comment)>, or unsubscribe< https://github.com/notifications/unsubscribe-auth/AR67PKWZ7HJ6RCQ3J47BJDLUEGFPHANCNFSM5E43VJ6Q>. Triage notifications on the go with GitHub Mobile for iOS< https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android< https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#24 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AA7XCSDODUZPZQYEWYOMBMTUEHJUJANCNFSM5E43VJ6Q> . Triage notifications on the go with GitHub Mobile for iOS <https://apps.apple.com/app/apple-store/id1477376905?ct=notification-email&mt=8&pt=524675> or Android <https://play.google.com/store/apps/details?id=com.github.android&referrer=utm_campaign%3Dnotification-email%26utm_medium%3Demail%26utm_source%3Dgithub>.

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