i connected the max232 with its components(4 1uf capacitors).

in the datasheet of the max it says that if the pin T1in or T2in received low voltage the o/p will be high if the i/p is high then the o/p is low.

in my case the i/p voltage is 1.5v and the o/p is 3.7v !!!

should the o/p be 12v to transmit the signal to serial port?

i am supplying the max232 with Vcc=4.6v so what's wrong with it?

 

The Max232 is an inverting voltage doubler.

1.5V is below the minimum threshold (2V Guaranteed, 1.5V typical) for a high signal. Check the datasheet

 

i tried to input 2 and 3.5 voltages but the output still very low?

 

Post a schematic of the entire circuit, the problem may be somewhere else, or it could be connected wrong in wiring.

 

now the first problem is solved but there is another problem

after supplying the max232 with Vcc(5v) i noted something strange
pins #10 and #11 are input pins but when measuring the voltage on them the multimeter reads 5v!!!

it's supposed to be 0 because i want to input TTL signal and max232 invert it to Rs232 level.

Note: i tried two different max232 ic's but the two have the same problem?

Thank you

 

after supplying the max232 with Vcc(5v) i noted something strange
pins #10 and #11 are input pins but when measuring the voltage on them the multimeter reads 5v!!!

it's supposed to be 0 because i want to input TTL signal and max232 invert it to Rs232 level.

Said who?

The internal schematic clearly shows two 400K pullup resistors on pin#10 and pin #11. This will cause your DVM to measure about +5V even when nothing is connected to these pins.

 

Pin 10,11 voltage being +5v makes the T1out and T2out -12 v so the serial device receives -12v all the time which may interrupt the communication and causes unexpected behavior from the device

 

When connected to logic, it will be held at 0 or +5. Are you not using it for this purpose? The pullup is to help open collector outputs of some logic ICs.