Garbage data problem from max232 circuit.

[haris115]

I automate the trainer at-5000 for my project. I designed the circuit using 8051 (AT89S51) controller that take the input from trainer seven segment and convert to the ASCII characters and display the data in the form of 456, 940 upto 999 via TTL to Max 232 circuit in hyper terminal.

The problem is that whenever connected my serial to usb converter to laptop, hyper terminal shows garbage data or some time no data arrive instead of showing 456, 940 upto 999.

I am using MAX232CPE with 10uf capacitors as charge up capacitor with cream shell connector coming form 8051 circuit and connected in MAX232 circuit.

Please experts tell me what will be problem that I am getting garbage data or no data in hyper terminal. I also check my programming but I didn't find any problem in programming.

 

[alexxx]

I am using MAX232CPE with 10uf capacitors as charge up capacitor

10uF sounds like a quite large capacitance. Could you post the datasheet you followed for your design?

 

[zivoradbre]

Did you choose right baud rate in terminal? If you baud rate is properly chosen, than problem may be internal noise or bad ground signal.

If you post your circuit, maybe people can help more....

 

[haris115]

Please tell me 10uf capacitors are fine or not ???? because I notice from max 232 datasheet that 1uf is recommended. Can 1uf use for this purpose???

Yes I correctly choose the baud rate in terminal which is 96000. I have make my pcb design instead of schematic design. I am posting both of them.

Also I am using 10uf charging capacitors, is this fine?? because I found from datasheet that 1uf can be used with max232 only. Should I replace 10uf to 1uf capacitors?????? Also I attached my pcb design pic. Please help me.

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I didn't checked the datasheet of max232. According to datasheet only 1uf capacitors can be used with max232. Now Please tell me either I replace 10uf with 1uf or 10uf is fine with my circuit????

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@alexxx

I didn't checked the datasheet of max232. According to datasheet only 1uf capacitors can be used with max232. Now Please tell me either I replace 10uf with 1uf or 10uf is fine with my circuit????

 

[alexxx]

I didn't checked the datasheet of max232. According to datasheet only 1uf capacitors can be used with max232.

OK then. So use 1uF! If the problem then remains, you can search for other stuff as well, like baudrate.

 

[doraemon]

Hello!

Please tell me 10uf capacitors are fine or not ???? because I notice from max 232 datasheet that 1uf is recommended.
Can 1uf use for this purpose???

Your question sounds strange. Or is it a typo? If the maker recommends 1µF, why do you use 10? It's just looking for
trouble. And if it's 232A, then use 0.1µ everywhere.

Dora.

 

[MUKESH.K.S]

MAX 232 works fine only with 1uf capacitor. Use 1 uf electrolytic capacitors as in the circuit given below. Give 5v to the max232 and check the voltages at pin 6 &pin 2. The pin 2 will show 8.5v and pin 6 will show -8.5v. Then your circuit will work fine. The capacitors are charge pulling capacitors, max232 converts 5v to rs232 level by using the charge in these capacitors. So if u change the value of these capacitors it not going to work as desired,