Problem with MAX232

Discussion in 'General Electronics Chat' started by shom_show, Apr 23, 2012.

  1. shom_show

    Thread Starter New Member

    Sep 4, 2010
    15
    0
    Hi,

    I am facing a problem with MAX232 DUAL EIA-232 DRIVERS OR RECEIVERS.

    After doing the necessary connections with (1uF) capacitors and with

    ATMEGA32, whenever I am powering up the IC with 5 volt, it is getting heated

    up. Can anyone please help me in sorting out the problem.


    Sumanta

    Indian Institute of Technogy Khara  gpur, India 
    
    
     
      
    
    
     
    
     
  2. panic mode

    Senior Member

    Oct 10, 2011
    1,318
    304
    post circuit and exact part number (there are many variants for different voltage and cap size).
     
  3. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    Hey I thought (not sure) IIT Kharagpur is one of the best IIT collage in India ,they should at least teach this stuff to their students ,its not a big deal. Are you really a student of IIT Kharagpur ???

    Anyway ,recheck all the wiring, check the polarities of the capacitors...specially on the voltage doubler section pin 2 and voltage inverter section pin 6 ,many noobs make a mistake their.Their will be -10VDC at pin 6 and +10VDC at pin 2 if every thing is correct.

    You can post a picture of your circuit... both side component and wiring.

    Welcome to AAC and about your location Shibpur is not in Kolkata

    Good Luck
     
  4. shom_show

    Thread Starter New Member

    Sep 4, 2010
    15
    0
    Hi,

    Actually I am working as a Project Assistant in IIT Kharagpur. Please find the

    complete circuit in the Attachment. I have checked that correct polarities of the

    capacitors are connected with (MAXIM MAX232CPE +0902). But still the IC is

    getting heated up with powering up with 5 volt DC.



    Sumanta
     
  5. panic mode

    Senior Member

    Oct 10, 2011
    1,318
    304
    i have used exact the same part on couple projects and your schematic for MAX232CPE is (almost) straight copy from the datasheet. the only differences are:

    - power pin polarity is not shown. (+5V should be pin 16. GND is pin 15)
    - negative size of C9 should go to +5V, not to GND

    actually if C9 voltage is rated sufficiently high that should not be a problem (you don't have there 6.3V part, do you? should be at least 16V).
    other things to check: all connections, any shorts or loose connections, voltage on each pin (+10V on pin2. -10V on pin6, +5V on pin16, 0V on pin 15, there should be 5V across other 1uF capacitors etc.)

    otherwise - there is not much to go on, one possibility is that the MAX232CPE is damaged.
     
  6. shom_show

    Thread Starter New Member

    Sep 4, 2010
    15
    0
    In this circuit I am using (1uF, 63 volt) capacitors, so you have mentioned that

    higher rating will not be a problem. I have replaced the IC with another MAXIM

    MAX232 EPE +0826. Now I have connected the -ive end of C9 with +5 volt. The

    IC is not getting heated up, but the corresponding voltages obtained are -

    1) 9.34 volts at pin2,

    2) -8.85 volts at pin 6

    3) 5.09 volt at pin 16

    4) 4.75 volts across C7

    5) 9.06 volts across C8

    6) 4.28 volts across C9

    7) -9.03 volts across C12

    The voltage across the capacitor C8 is (9.06 volts) which is too high than the

    normal value (+5.00 volts). Can you please address the problem.


    Sumanta
     
  7. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    Hmm are you sure you are on the staff and not a student:rolleyes: Anyway student or staff. I suggest you read up on RS232 and voltage levels. And also read the datasheet http://datasheets.maxim-ic.com/en/ds/MAX220-MAX249.pdf That will address the problem (if it is any at all)
     
  8. debjit625

    Well-Known Member

    Apr 17, 2010
    790
    186
    As I already said most noobs make this mistake i.e.. connection for voltage doubler section is wrong,connect C9 between pin 2 and +5VDC ,positive side of the capacitor will be at pin 2 and negative side will be at +5VDC.Also add a filter capacitor of 1uf.

    t06afre already gave you the link for the datasheet,on that datasheet you could find how to connect the capacitors in figure 5 at page 17.

    After doing this you will find near -10VDC at pin 6 and +10VDC at pin 2.

    Right now I am also working on a datalogger (personal project) for electrical signals,I am using PIC and USB for communation with PC.

    Good Luck
     
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