EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: lk on October 24, 2012, 02:31:41 pm
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Greetings
I decided to battle with my long time Nemesis, the rs232 port, so i made myself a TTL to RS232 converter using the max232. And what i discovered is that there is almost 2 volts of ripple on the TTL side (pin 12 on the MAX232) and that fact surprised me somewhat, i can see that it does send my signals trough from the PC serial, I'm just curious if this is normal. I did not notice any ripple on the RS232 side.
I have anotherone of those converters i bought and that one exhibits the same ripple.
I guess what I'm asking is if this ripple is normal or i should just ignore it?
-lk
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Sounds a bit strange. What frequency is the ripple? Have you got decoupling on the chips' power?
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Max232, did you use the correct supply decoupling caps in the suggested layout, with them connected correctly. Cheap ones often do not use the right value caps.
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Thanks,
was the newbie decoubling cap again :( picure 1 is before he cap and picture 2 is after.
I used a 10uf and that solved it, i guess i was baffled by the fact that the datasheet, atleast the part where i looked said that 4 caps are all that is needed, i used 4 ceramic caps, and did not think any more of it :)
-lk