[E3-hacking] Universal E2/E3 serial interface design
ian.stirling at mauve.plus.com
Sat Jan 21 15:02:27 GMT 2006
> As per my earlier posting I've now designed and built a universal E2/E3
> interface board that should convert to/from legal RS232 levels. A jumper
> is used to select E2 or E3 mode. I've also produced a circuit diagram
> from my prototype and put this here:
> I would welcome any feedback on the design and would also appreciate
> people sanity check I've not put any stupid mistakes in the circuit
> diagram when copying from my stipboard prototype.
The 1K resistors are not quite adequate protection on the input of IC1A.
A static spark could easily generate 2Kv, or a 2A pulse.
This will probably not kill the 4070 the first time.
Four diodes, one each between the tip/ring connections, and VCC/ground
would be a good idea.
1Nn4148 or similar would be fine.
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