RS232 Serial isolation repeater

arber333 · Post by **arber333** » Mon Jul 04, 2022 8:00 am

I need to isolate serial port of my RPM and speedo chip.
I am designing a new board. I want to use serial information i.e. from SOC device or other on the input where the output would be CAN bus telegram information. My SOC device is powered from HV and i cant connect its serial GND to car chassis.
Anyone has any idea or schematic how to implement isolation to serial bus?

Pete9008 · Post by **Pete9008** » Mon Jul 04, 2022 8:46 am

There are lots of ways of doing it depending on how cost sensitive it is and how much isolation you need. A good starting point is the Analog iCoupler range https://www.analog.com/en/parametricsearch/11037#/, easy to use and reliable but do tend to be a bit of a premium price product.

Pete9008 · Post by **Pete9008** » Mon Jul 04, 2022 9:03 am

Assuming you can isolate at the TTL side and only need Rx and Tx then one of these would be worth a look https://www.analog.com/media/en/technic ... 5_2286.pdf. It still seems to be available from stock too.

Edit - changed part to one with a 5kv isolation rather than 3kv. Note - it's up to you to ensure that this satisfies your safety requirements.

arber333 · Post by **arber333** » Mon Jul 04, 2022 9:14 am

Pete9008 wrote: ↑Mon Jul 04, 2022 8:46 am There are lots of ways of doing it depending on how cost sensitive it is and how much isolation you need. A good starting point is the Analog iCoupler range https://www.analog.com/en/parametricsearch/11037#/, easy to use and reliable but do tend to be a bit of a premium price product.

Tnx, what you suggested led me to this chip ADuM1201. http://lemmini.de/RS232%20TTL%20Isolato ... lator.html
https://cdn-reichelt.de/documents/daten ... 0_1201.pdf
Seems i can directly use it with my Arduino board i only need to provide 5V DCDC supply. ADUM1201 has reversed I/Os for use as TX/RX signal.
Should be simple enough...

tnx

Pete9008 · Post by **Pete9008** » Mon Jul 04, 2022 9:16 am

Sorry, just edited my last post while you posted yours, I'd change to a ADuM2281 as it has a higher spec for the isolation voltage.

Is this for electrical isolation or for safety isolation?

Pete9008 · Post by **Pete9008** » Mon Jul 04, 2022 9:22 am

arber333 wrote: ↑Mon Jul 04, 2022 9:14 am
Pete9008 wrote: ↑Mon Jul 04, 2022 8:46 am There are lots of ways of doing it depending on how cost sensitive it is and how much isolation you need. A good starting point is the Analog iCoupler range https://www.analog.com/en/parametricsearch/11037#/, easy to use and reliable but do tend to be a bit of a premium price product.
Tnx, what you suggested led me to this chip ADuM1201. http://lemmini.de/RS232%20TTL%20Isolato ... lator.html
https://cdn-reichelt.de/documents/daten ... 0_1201.pdf
Seems i can directly use it with my Arduino board i only need to provide 5V DCDC supply. ADUM1201 has reversed I/Os for use as TX/RX signal.
Should be simple enough...

tnx

That all looks good. They are very easy to use. It's just a case of choosing one that has the number of transceivers and isolation that you need and connecting it up.

arber333 · Post by **arber333** » Mon Jul 04, 2022 10:24 am

Pete9008 wrote: ↑Mon Jul 04, 2022 9:16 am Sorry, just edited my last post while you posted yours, I'd change to a ADuM2281 as it has a higher spec for the isolation voltage.

Is this for electrical isolation or for safety isolation?

More like electrical isolation since i cant bring chassis GND and HV GND together!

EDIT: OK i made a sample design and i will put my speedo RPM serial circuit to production. Ill post my findings here...

RS232 Serial isolation repeater

RS232 Serial isolation repeater

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Re: RS232 Serial isolation repeater

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Re: RS232 Serial isolation repeater

Re: RS232 Serial isolation repeater

Re: RS232 Serial isolation repeater