Opto-isolator between RS232/TTL board and generator?

[wrvolz]

Checklist

• I made sure that there are no existing issues or discussions - open issues,closed issues,open discussion, closed discussion - which may answer my question or that I could contribute my information to.
• I have read the Known Issues Wiki Page and my question / issue is not listed.
• I have provided the version of the software and the operating system in my post.
• If I have an issue with genmon not communicating with the controller, I have read and followed the serial troubleshooting guide.
• I have included the generator make and model in my submission.

Version

1.19.05

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What is/are your question(s)?

I continue to have issues where the TTL/Serial board dies when there is a power outage. Not all the time but I need to replace it several times a year. I think the issue is coming from a voltage spike from the generator (If it came from the POE Ethernet it'd probably kill the RPI). I'm wondering if I can insert an opto-isolator between the serial board and the generator. If so exactly how would I do that? Would I need to do both RX and TX and use two Opto's? I've not used an Opto before so I'm not sure exaclty what they would do electrically. I don't want to blow the generator board or RPI either. The TTL boards are cheap but they always blow at the wrong time.

If I did this would I still need to ground the RPI to the Generator battery negative/ground? If not, where would I get the ground from the generator (negative battery?)?

Thanks

Here's an example opto:

https://www.amazon.com/DAOKAI-Optocoupler-Isolation-Converter-Photoelectric/dp/B09TK2WQXD/?encoding=UTF8&pd_rd_w=rY5lR&content-id=amzn1.sym.a602a706-e4fe-481e-98c3-9b75060fd322%3Aamzn1.symc.abfa8731-fff2-4177-9d31-bf48857c2263&pf_rd_p=a602a706-e4fe-481e-98c3-9b75060fd322&pf_rd_r=ABPTH3KNNTBSR83PWRZE&pd_rd_wg=K8ozN&pd_rd_r=436a24a7-9784-4065-812c-40de2fcae02c&ref=pd_hp_d_btf_ci_mcx_mr_ca_id_hp_d&th=1

Additional information

Generac 20Kw Model G0062500. RPI 3, Bookworm.

[jgyates]

I do not the the device in the link will work on RS-232 as it does not appear to support negative voltages. Possibly something like one of these:

https://www.amazon.com/Powered-Serial-Electric-Isolator-protect/dp/B01EACRB0K/

https://www.amazon.com/waveshare-USB-RS232-485-422/dp/B0BTYKS8LK/

If using an isolated port, the generator side of the isolator would need to be connected to the ground of the generator RS-232 port and the RPI side of the isolator would be connected to the RPI ground.

The RPI should be connected to the power and ground of the power source that is powering the RPI. If that is the battery, then the battery ground, if that is a wall socket with a UPS, then the ground from the UPS.

The power source ground should be the same as the RPI RS-232 ground.

[jgyates]

your ground for two sides of the isolator should not be connected.

[skipfire]

Be aware, many opto-isolators must have power provided on both sides.

If you want a ready packaged option for a Generac, I sell a USB Molex adapter that does have an opto-isolator. https://pintsize.me/store/ols/products/molex-to-usb-converter

[wrvolz]

This sounds like a better option. So I'd plug this into he generator using the short molex cable and the other side using a short 1 ft usb-c to usb-a to one of the RPI usb -a ports. Then remove the ground wire from the RPI to the battery ground. The RPI is powered from POE split off from the Ethernet cable. Also change Genmon to use the appropriate USB ports.\ Sounds like a 10 minute fix. Thanks Bill Volz 832-724-5183 On 5/25/2025 6:13:52 PM, Jon R. Helms ***@***.***> wrote: Be aware, opto-isolators must have power provided on both sides. If you want a ready packaged option for a Generac, I sell a USB Molex adapter that does have an opto-isolator. https://pintsize.me/store/ols/products/molex-to-usb-converter [https://pintsize.me/store/ols/products/molex-to-usb-converter] — Reply to this email directly, view it on GitHub [#1291 (reply in thread)], or unsubscribe [https://github.com/notifications/unsubscribe-auth/AKSTMAEGYZDJQ77TWVG27P33AI6BLAVCNFSM6AAAAAB54GQYKSVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTGMRWGYYTMOI]. You are receiving this because you authored the thread. Message ID: ***@***.***> [fd20f2a2-3978-400b-ba42-0128a039aa73]

[skipfire]

Yes, that's all correct, and the port is usually /dev/ttyUSB0.