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GSM Modem SIM300 get hang after NO DIAL TONE

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cmsrlabs

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I am working on GSM Modem SIm300 with 8051 Micro.
When i got message NO DIAL TONE from modem, Micro gets hanged up.I tried reset Command also to reset GSM Modem but with no success.
To solve it i gave a delay of approx 2 minute. After that it work properly. Any idea to solve it without using delay.
One problem arises. When i made a call to only one number again and again, it works properly. But when i call to two numbers one after the other in a loop, it works only for one time and after that micro gets hanged.

Any idea to solve above two problems.
 

Where did you give 2 min delay ? at first dialing after power up ?
Hangup can occur if it doesn't have enough time to do the internal works, hence it is normal to have a delay in modem routines; Allow 1 or 2 minutes to initialize modem at start up.
 
problem get solved by applying 2 minutes delay after power On....then 2 second delay after each command issued to GSM Modem..
Now i am able to call to as many number as i want..
Thanks.

Now i am going to design a Battery Charger Circuit to charge 12 Volt 7 Amp. I need all features in this design like Trickle Charging, Control Charging Current, When Battery Voltage reaches below lower limit, the load gets cut off to avoid deep mode .

Any suggestion to start it. Is there any specific ICs available.
 

Hi,
Nice to know it's working !

What is the type of battery you need to charge ?
There are several ICs available for battery charging. Selection is depend on type of battery, current. Those are having the features you need. Search websites of Maxim IC and Texas Instruments; (eg. BQ24450 from TI).
Also there are other charging circuits without using specific ICs. Search EDABOARD threads and web for battery charging circuits with type of your battery and current.
Hope this helps you,
 

I want to use 12V, 7A Lead Acid Battery.

What is best to use. Specific IC or design it using SCR or transistor??

I also want to display the charging status of battery in real time as we in case of Laptop/Cell Phone

- - - Updated - - -

I want to use 12V, 7A Lead Acid Battery.

What is best to use. Specific IC or design it using SCR or transistor??

I also want to display the charging status of battery in real time as we in case of Laptop/Cell Phone
 

Anybody have idea about Dual SIM GSM MODEMS

- - - Updated - - -

Anybody have idea about Dual SIM GSM MODEMS
 

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