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Hi I'm trying to find a cheap solut

Hi I'm trying to find a cheap solut

(OP)
Hi I'm trying to find a cheap solution for a galvanic separated point to point RS485 bus. I need to send data between these 2 points in 1/2 duplex. There are full solutions for it like the www.linear.com/product/LTM2881 however these are very expensive and I would blow my complete budget on these babies.
There are some other standard solutions with opto couplers and a 2nd power supply however I don't like these either.
I came up with this idea (more or less based on the old appletalk or local talk as it was called I believe.) using 2 pulse transformers on both ends of the line.
I'm going to use manchester coding at a 100Kbits/sec data rate.
My question anybody any better ideas/suggestions?, any people having experience with this kind of set-up?, any advice type/model for the pulse transformers? my budget is max 2€ per point to point link on materials.
so including resistors, capacitors schottky diodes etc Excluding PCB, design costs etc.
All help/pointers welcome.

Thanks Jan Z.





RE: Hi I'm trying to find a cheap solut

(OP)
Hi IRstuff no not really from aprox 2 meter up to 100 meter.. I'll have a look at the systems you mentioned. Thanks for your reply

RE: Hi I'm trying to find a cheap solut

(OP)
Sorry took me a while to grasp the abbreviations no infrared and bluetooth isn't really an option. Really need to use good old copper. Also had a look at plastic fiber what might be a potential solution but is also too expensive and too fragile at the connector sides. Main use is machine building.

RE: Hi I'm trying to find a cheap solut

Depending upon quantity, your magnetics may blow your budget. Depending upon what mag you choose, you could be anywhere from $1 to $2/each. Choose wisely...

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Hi I'm trying to find a cheap solut

(OP)
The ethernet idea would be a possibility however the chip is .80$ but also there is a 2 to 3$ pulse transformer used. (HX1198FNL). Also the ethernet is full duplex and I was thinking more like half duplex. I'll have a look if a re-design to full duplex would make sense. I'll also have a look at the 10base T standards and see if it helps me. Thanks for all the help so far I'll keep you posted.


PS. "Dan" don't what your link means I can't open it?

RE: Hi I'm trying to find a cheap solut

(OP)
Look what I found! Link Galvanic seperation with capacitors! Now we are talking this would cost a standard driver chip and a few cents more.
But with a 10 lower frequency would mean a lot more phase difference and with capacitors on both sides of the cable would that mean doubling the capacitor size.....Wonder if it would work.... Food for thought All comments welcome!

RE: Hi I'm trying to find a cheap solut

Just make sure you read the Capacitor Selection (Clause 5) very carefully. How much potential are you attempting to isolate?

Z

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