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I am looking for a simple circuit to use a picaxe 08m to control rs232 to relay driver? Answered



max232 or similar, if you're talking about TTL to RS232 in a pinned pkg.
(max 232CPE runs ~$3/ea from digikey or similar distributor)

requires 1 chip and a resistor an small cap. 2 resistors and 2 caps for a 2 channel, powers from 5V supply.

Ref design included in the data sheet

see www.maxim-ic.com

I don't know why folks still recommend the 232. The 202E is a lot easier to use, because it only needs 100n caps, and it has a higher input protection rating.


As you say, with the need for only 0.uF caps, it sounds easier.

Primarily a habit of familiarity. I used hundreds of those over the years in one offs. I used the ESD protected version..can't recall but I think it was 15kV.

I haven't actually wired one up in ~6 years or so, so it's just a memory (although I have a half tube of them in storage)...They were just a dependable choice in both the experimental and industrial areas I supported.

Max232 sounds good to me.
Make sure you're able to isolate the the serial out pin or separately power the relay board otherwise all sorts of strange things will happen during PicAxe programming.