max 232 circuit

[ghostman11]

hi guys i have tried to use the search function on the site but for the last few days it dosnt seem to be working. so forgive me for asking but does anyone have a diagram for using a max 232 with a pic, showing the caps etc/
many thanks

 

[ericgibbs]

hi guys i have tried to use the search function on the site but for the last few days it dosnt seem to be working. so forgive me for asking but does anyone have a diagram for using a max 232 with a pic, showing the caps etc/
many thanks

hi J,
This should help.

Eric

 

[ghostman11]

thanks eric thats just what i was after!

 

[ghostman11]

after having a look at the chip it turns out i have a 231 the datasheet here http://www.datasheetcatalog.org/datasheets2/45/453523_1.pdf figure 10 on the right hand side diagram shows pin 14 as being 7.5v-12v in. so does that mean i cant use it with my 5v supply? also the datasheet states it uses 2 external caps but shows 3 in the diagram. so how do i hook up this particular chip?

 

[ericgibbs]

after having a look at the chip it turns out i have a 231 the datasheet here http://www.datasheetcatalog.org/datasheets2/45/453523_1.pdf figure 10 on the right hand side diagram shows pin 14 as being 7.5v-12v in. so does that mean i cant use it with my 5v supply? also the datasheet states it uses 2 external caps but shows 3 in the diagram. so how do i hook up this particular chip?

hi J,
The way I read the d/s for the MAX231 is that it has no internal charge pump, so it it requires a 7.5 to 12V supply, as well as the 5V.

**broken link removed**

 

[ghostman11]

thanks eric! looks like i did an ordering booboo then :S anyone want 30 max231 chips lol

 

[ericgibbs]

hi J,
What voltage is the input to the project 5V regulator.?

 

[ghostman11]

i am not using a regulator eric (i rarely do) its just a straight 5v feed, i could i spose use a reg and 12v supply, while i go slap myself for careless buying

 

[OlPhart]

Don't beat yourself up too bad, there are a Bunch of flavors in that series.

I like Erics' take: a locally regulated +5 is more stable, and fed from a ~+9 does the 231. No sense orphaning $60+. Good Hunting... <<<)))

 

[micr0man]

i thought the RS232 standard allowed +-5v input, if so there is a small chance of the max231's working on 5v. Its worth a try

 

[OlPhart]

Well, the spec is only >+/<- 3V, but the 231 has ~7.5 -> 13.5 volt span...

 

[Pommie]

You could always use the PWM module of the pic to make a simple boost converter.

Mike.

 

[ghostman11]

that sounds interesting mike, care to explain???,

 

[Wilksey]

The MAX231 is for external RS232 voltage references, i.e. no charge pump.

For a cheap pin compatible version of the MAX232 look up EXAR (SIPEX) 232 on Farnell, just over £1 each, and they work with 0.1uF caps!! Which I have a ton of.

I think what Mike was referring to was using the PWM of the PIC to boost the output voltage from 5v to 7.5-11V for your reference, my USB->232 levels sit at +/- 8.8V, my PC RS232 port sits at +/- 10.5V, such a wide range!

Look here: https://www.ladyada.net/library/diyboostcalc.html for some interesting reading!

The reason it the image shows 3 caps is because one is a filter cap, and there are 2 main caps on C1 + C2 that make the circuit work.

HTH
Wilksey

 

[Pommie]

that sounds interesting mike, care to explain???,

Have a read of this thread.

Mike.

 

[ghostman11]

great to0 see you wilksey!! hope your well thanks for the info i will order some "propper chips "
thanks for the link pommie interesting stuff! give me plenty to read

 

[Wilksey]

Great to see you also Ghostman, hope you are doing well!

I think the 232 chip was one of the first things I ever hooked up to a PIC, you can get another variant of the chip with no need for external caps, they are very expensive though!