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Making a Max232 Cable

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Phil2003

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max232 cable

Hi guys, its my first post here.

i tried making a serial cable for my modem with a max232 chip and 4 1uf 63v caps. i used this plan:

**broken link removed**

it dont works...by coincidence i short circuit some solderings and got a positive reaction, seems like somethings missing on this plan?!

it would be great if anyone has a hint for me, cause im not such a great electrician... :(

thanks
phil
 

max232 schematic

I am afraid the MAX232 chip will not operate correctly with 3.3V as it is designed for 5V. You should try a 3.3V Max232 instead ...

best regards
 

max232 3.3v

In DB9 plug connect:
pin 7 with 8 - this are RTS and CTS signals
pin 4 with 6 - this are DTR and DSR signals.
Some modems working with handshaking and need this connections.
 

max 232 cable

thanks for your replays guys!

forgot to say that i use 5v from within the modem, not 3.3!

i will try what u suggested arturt134 and tell you if it helped or not!
 

max233 schematic

didnt help, i got nothing on hyperterminal :(

i got 2 times with luck the bootsequenz on the hyperterminal as i shortcutted some solders from the chip...if i just knew which one that were!
 

max232 serial cable

You should use a MAX3232 instead of MAX232. MAX3232 is made for 3.3 V.
You can order free samples from www.maxim-ic.com

For capacitors C1-C4 use 100nF (0.1µF).
 

cable max232

as i said, i use a 5v line, not a 3.3v as shown in the schematic, so it should be no problem. a max233 would be better, but its hard to get in my country (didnt find a shop here in austria).
 

max232 schematics

Phil2003 said:
as i said, i use a 5v line, not a 3.3v as shown in the schematic, so it should be no problem.
Click to expand...
Yes it is a problem, because the cellphone in your schematic can only handle 3.3V.

Phil2003 said:
a max233 would be better, but its hard to get in my country (didnt find a shop here in austria).
Click to expand...
As I said you can order free samples from www.maxim-ic.com so it doesn't matter where you live. And it is free!

If you live in Austria you can also order electronic components from here: www.farnell.com but it's not free.
 

3.3v max232

i just ordered a max233 :D

hmm so this is the wrong schematic for 5v! maybe it works with 3.3 also, have to try it.

thanks
phil
 

max232 3.3

I don't understand where you get 5 V from and why you use it?
In your schematic there is only a 3.3 V voltage source.

And why do you order a MAX233 when you need a 3.3V compatible device like MAX3232?

The best might be to order a DS276 instead. This one doesn't need any external capacitors and can operate from both 3.3V and 5V.
**broken link removed**

Anyway you can just order both, since you can order up to 10 devices from MAXIM samples.
 

how to make a max232 cable

im sorry, i expressed myself wrongly!

i want to make a 5v serial cable, and now i know i used a wrong schematic...omg to be true, its the first time i soldered something! *gg*

so i need a 5v schematic for max232...when my 233 arrives, im gonna use it, but in the meanwhile i try to solder the max232 the right way!

anyone who has a 5v schematic? :D
 

schematic max232

Remeber you should always connect a capacitor from Vcc tog GND.
In the MAX232's data sheet it is called C5 in figure 5.
This capacitor should also be connected if you use an IC with internal capacitors like MAX233, see figure 11.

There is no difference between a 3.3 V schematic and a 5V schematic.
The connections are the same, the only difference is the voltage used.
Just remeber C5 as shown in figure 5.
 

max232 3.3 v

Here's a schematic using MAX233:
serial.gif

https://www.rockhounding.net/projects/compass/parts/serialport/max233a.html
I don't know why he has connected pin 1 to pin 20, there is no need for that, they can just float.
But remember to connect a 1µF capacitor between pin 7 (Vcc) and pin 6 (GND) as reccomended in figure 11 of the data sheet.

And here's one using DS276:
ds276_circuit.gif

https://www.rockhounding.net/projects/compass/parts/serialport/
 

using max233

You can alson order free RS-232 sample IC's from Sipex. Sipex SP233 is the same IC as Maxim MAX233:
**broken link removed**
The best one is SP233E which have improved ESD protection.

I got ten sample IC's from Sipex some time ago.
 

max232 ttl cable

i made the cable now on the new 5v schematics, and it works now! ive ordered some 233´s, maybe i make a really good looking cable if i get them :D

thanx for your help guys!
phil
 

making max232 serial device

Are you plannig to uncap your cable modem?
 

max233 free sample

yep thats want i want to do. but to be true, i dont want to get faster speeds, cause i dont wanna loos my account. i just want to be _able_ to...just for my ego :D
 

max232cpe cable modem

Phil2003 said:
yep thats want i want to do. but to be true, i dont want to get faster speeds, cause i dont wanna loos my account. i just want to be _able_ to...just for my ego :D
Click to expand...
That's probably clever.
The cable company can watch if you mess with your cable modem.
I wouldn't dare to change my speed.

This is from the FAQ page:
Can my ISP detect an uncapped modem?
ISP's can ALWAYS detect an uncapped modem. They can do this via SNMP commands or QoS profiling. SNMP is in some cases able to be disabled, but QoS profiling is done head-end and is unavoidable.
 

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