Hello,

I am working on developing a driver circuit to send data from my PIC microcontroller to a PC using RS-232. While reviewing the datasheet for the MAX232 IC, I noticed that certain capacitors are required.


I have a ceramic capacitors with "104" written on it, and I believe its capacitance value is 0.1 µF (not 1 µF). Could you please confirm if my understanding is correct? Also, if I need a 1 µF capacitor, should I look for one marked as "105"?

 

That is correct.

104 = 10 x 10000 = 100000 pF = 100 nF = 0.1 μF
105 = 10 x 100000 = 1000000 pf = 1000 nF = 1 μF

Note that different RS-232 converter ICs require different value charge capacitors. Go with the manufacturer's recommendations.

 

The MAX233 does the same job without external capacitors, but if the MAX232 is what you've got, you'll have to install them. But RS-232, really, in this day and age? It's a hangover from medieval times.