[SOLVED] Strange Problem in the GSM modem

[ADGAN]

I'm facing a strange problem with my GSM modem. Recently by mistake I gave about 9V power to a wrong pin and the MAX232 IC got burnt. I got it repaired. I faced another problem after that. When I put the switch to the ON position the modem starts, but when I cut off power from the power supply without switching off the switch the modem doesn't start again. The modem that I'm using is TC35. Any idea what has happen?

 

[tushki7]

Greetings,
After switching it off, wait for few seconds/minutes. Does it helps?

 

[ADGAN]

No! Its not working that way either

 

[tushki7]

Have you disconnected DB9 cable before switching it off? Disconnect cable and then wait few minutes.

 

[ADGAN]

I'm not using the DB9 cable there is a pin which can be used to directly connect the microcontroller, I'm using that.

 

[tushki7]

And that pin is connected to ?

Remove every cable except power cable and try that.

 

[ADGAN]

TXD_MCU_TTL -- TX
RXD_MCU_TTL -- RX of the Microcontroller

 

[tushki7]

If your problem is solved mark thread as solved.

 

[ADGAN]

Already done. As you suggested it requires some time to start after switching off. Thanks

 

[tushki7]

That's because of those capacitors. :wink:

Have a good day !!

 

[ADGAN]

It requires 7 seconds between a Off and a ON. I was wondering whether it is possible to add a delay using a resistor and a capacitor? Is it possible?

 

[tushki7]

It requires 7 seconds between a Off and a ON. I was wondering whether it is possible to add a delay using a resistor and a capacitor? Is it possible?

Only 7 Seconds? How long did you waited before when i told you to wait.
Yes, you can add more delay by adding higher value electrolytic capacitor(e.g. 100uf, 1000uf most commonly used capacitors values for power supply) in parallel with power supply.

Good Luck

 

[ADGAN]

About 4 or 5 seconds. Thanks