hm_fa_da
Full Member level 5
Hi,
I'm currently designing a remote reading system which uses GSM module inside.
The device is going to pass for ATEX Zone 1 at least. IIC group.
I have some ideas and would be glad to know your comments.
The GSM module needs about 3.6-4.2V to work fine, consider it 4V.
The power source of the device is only battery inside the box, no other external power supply.
I use 3.6V Lithium battery (ATEX verified).
If i just use the battery voltage directly for GSM module, it's on low edge of working voltage. or in cold environment, the battery voltage may drop more ...
So i prefer to use a better and more stable solution to supply 4V for GSM module:
Solution 1:
I use two batteries in series, it makes 7.2V, and then i use LDO for GSM module. the problem is in this way i can't use high capacity capacitor for GSM module (Max permitted C for 7.2V is 13.5uF) and it gets problem on 2A surge current drawn by GSM module. it needs high capacitor near to module ...
In this situation i think a solution is to use GSM module and the LDO circuit in a separate small box and go for compound encapsulation method not IS for this part ! i saw this solution in an ATEX passed device. they used up to 3000uF capacitor for GSM inside the small encapsulated plastic box.
I think this way i even can use Buck switching regulator (with inductors and capacitors which are out of permitted value in I.S method) inside the encapsulated box without problem, is it true ?
Solution 2:
I just use 1 x 3.6 Lithium battery, then i use a step up booster with 4V output (To be sure if battery voltage drops, The module still works) ! the booster needs only 4.7uH inductor. for 4V Voltage, with safety factor of 1.5, the maximum permitted capacitance is 600uF which is enough for my purpose.
I even can use merged solution of 1 and 2 for better safety, i mean i use solution 2 inside the compound encapsulated box ...
I'd be thankful to know your comments.
- - - Updated - - -
For solution 2, I also found a booster chip which needs less than 1uH inductor. the stored energy would be 8uJ (less than permitted 40uJ) with 4A current through inductor ...
I'm currently designing a remote reading system which uses GSM module inside.
The device is going to pass for ATEX Zone 1 at least. IIC group.
I have some ideas and would be glad to know your comments.
The GSM module needs about 3.6-4.2V to work fine, consider it 4V.
The power source of the device is only battery inside the box, no other external power supply.
I use 3.6V Lithium battery (ATEX verified).
If i just use the battery voltage directly for GSM module, it's on low edge of working voltage. or in cold environment, the battery voltage may drop more ...
So i prefer to use a better and more stable solution to supply 4V for GSM module:
Solution 1:
I use two batteries in series, it makes 7.2V, and then i use LDO for GSM module. the problem is in this way i can't use high capacity capacitor for GSM module (Max permitted C for 7.2V is 13.5uF) and it gets problem on 2A surge current drawn by GSM module. it needs high capacitor near to module ...
In this situation i think a solution is to use GSM module and the LDO circuit in a separate small box and go for compound encapsulation method not IS for this part ! i saw this solution in an ATEX passed device. they used up to 3000uF capacitor for GSM inside the small encapsulated plastic box.
I think this way i even can use Buck switching regulator (with inductors and capacitors which are out of permitted value in I.S method) inside the encapsulated box without problem, is it true ?
Solution 2:
I just use 1 x 3.6 Lithium battery, then i use a step up booster with 4V output (To be sure if battery voltage drops, The module still works) ! the booster needs only 4.7uH inductor. for 4V Voltage, with safety factor of 1.5, the maximum permitted capacitance is 600uF which is enough for my purpose.
I even can use merged solution of 1 and 2 for better safety, i mean i use solution 2 inside the compound encapsulated box ...
I'd be thankful to know your comments.
- - - Updated - - -
For solution 2, I also found a booster chip which needs less than 1uH inductor. the stored energy would be 8uJ (less than permitted 40uJ) with 4A current through inductor ...
Last edited: