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circuit to add to protect circuit from damage

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yassin.kraouch

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Please i need help : i have two separated electronic cricuit that communicate via uart, see attached, i didn't put directly the RX and TX of the two circuit i added transistor, i need help on how to protect my circuit from ESD or another protection
 

Hi,

I dont think you can get a better result if you use any protector circuit in between the Rx and Tx lines....

Better you can do is to do some external protection.... Use of Shielded cables can be done.....


Good Luck,

Sooraj.
 

If you add a pair of diodes to each input and output at the transistor base/collector. one diode anode to ground, cathode to base/collector, another anode to base/collector , cathode to Vcc. This will clamp any incoming voltage on the line to, between, ground-.8V or Vcc +.8V.
Frank
 

yes but ùy problem is how to choose the diode, can you help me on this ,
 

I would use optocoupler like PC817 to avoid voltage mix
 

Series resistors (of not too small physical size!) already provide a lot of protection since they help to limit peak currents. Same goes for buffer transistors on inputs & outputs since they provide alternative current paths in case of ESD events. Proper connectors & cabling can make sure that ground points always contact before signal pins, making ESD problems unlikely (at least, from connecting/disconnecting equipment).

If you think that's not enough, why not use something like what's used for MIDI equipment: www.midi.org/techspecs/electrispec.php

Serial interface, electrical isolation via fast optocouplers, TTL-level signals in & out, simple to put together. Looks right up your alley... :smile:
 

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