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Author Topic: Question about long wires and ardino  (Read 2200 times)
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Valencia, Spain
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Your main problem will be getting enough volts to appear at the end of the wire
I googled the DC resistance of Cat5 cable and got results of 95 Ohm / km ( or 50 Ohm / km )
40 m is less than 5 Ohm. A 10..20 mA current sees a hardly measurable voltage drop  less than 0.1V

TTL inputs have about 250 Ohm resistance (5V@20mA) so you'll be OK if that's what the input on the board is...

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

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What part did you look up that needed 20mA of current to drive it?  That doesn't sound correct at all.

Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at
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Hi Guys,
Thank you all for your help.

after some investigation I decided to implement my project as follows:
every sensor will have "minimal arduino" atmega8+few extra components.
The minimal arduino will be connected to enc28j60(there are some 3-4$ modules in ebay and I already have one of them).
The network topology will be driven from router and switches.Every sensor will have its own IP and will use TCP/IP to publish its values two one PC.The PC will handle the data from all 1000+sensors and notify the user with the analized data.
I think that my minimal arduino(with simple atmega8)+enc28j60 will cost me 6-7$ so I think its the best solution.
Using the TCP/IP solution above I think that I have few benefits. need to worry about long wires,package resubmission etc...
2.the topology will be simple and cheap network topology driven by router and many switches.
3.My arduino code will be very simple(just reading from ultrasonic sensor ) and my complicated code will be standard desktop software.

Now I will work on building extremely simple and cheap arduino based on atmega8 and connecting it to enc28j60.Hope its possible-I don't know jet if the existing enc28j60 library can fit into 1kb.If not I will use the more expensive 328 chip.


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