Problems with SIM300 as it doesn't detect the sim card

[GSM Man]

sim300 circuit with pic

You have to set the band(s) you want it to use - the SIM card has nothing to do with the bands used.

 

[galama]

sm bl not ready in modem

Hi all !
Anyone help me , I'm working with sim300d module for our GPS tracking system but it seems that I can't make the sim300d module work .
When I try connect my circuit ( I design by my self ) with PC , sim300d module didn't send anything to Hyper Terminal . I attach schematic of our project here .

Please show me what I wrong in my circuit . Thanks in advanced.

 

[pisoiu]

www.utoolkit.com/gsmeval.php

Why on earth would you put sim IO signal lines to ground with capacitor (c43,c40,c41) ? That will short sim lines to ground. The power supply for modem is wrong, you should have low esr capacitors to gnd at that point (at least 100uF). PWR key is not driven corectly, you should use a bipolar or mosfet transistor to drive it, not directly. Using the schootky diode to vbatt and power it from 5V you can exceed 4,5v supply and damage the modem. The netlight led is also not connected properly. Also, I am not sure, but I think the stabilizer you've chosen is not capable to support 2A peaks when gsm is transmitting. You've also connected the cpu which has 5V I/Os directly with the modem lines which has under 3V. You should use either e level translator or a CPU with 3V I/Os, or you will burn the serial interface of the modem. Also, when sending data to modem on tx line, make sure you keep rts to 0.
There's too many mistakes in the schematic, just take a look at the evaluation board schematic and copy what is there.

/pisoiu

 

[spider121112]

sim300_v7.03.pdf

Please help me to connect the main RX,TX of sim300cz EVB and pic16f877A Tx, Rx.

I need any tested schematic.

 

[vamsi.kodati]

debug rx sim300

Hi,
I am working on an avr-gsm project and am using sim300. I would like to know if sim300 can be operated by a 3.7 Li-ion battery with a boost converter to 4.2V??? Can anyone heelp me with this issue???

 

[jsidev]

sim300+led status

Hi,
I am working on an avr-gsm project and am using sim300. I would like to know if sim300 can be operated by a 3.7 Li-ion battery with a boost converter to 4.2V??? Can anyone heelp me with this issue???

The simxxx module work on 3.4-4.5V interval with Li-ion battery and boost converter is not necessary.

Powerup simxxx module by:
- Li-ion battery + charger(5-5.25V, 650mA limitation) or
- buck converter (step down) 3.6-4.2V, 2A peak current

Regards
Stephan

Added after 12 minutes:

Hi all !
Anyone help me , I'm working with sim300d module for our GPS tracking system but it seems that I can't make the sim300d module work .
When I try connect my circuit ( I design by my self ) with PC , sim300d module didn't send anything to Hyper Terminal . I attach schematic of our project here .

Please show me what I wrong in my circuit . Thanks in advanced.

The simxxx module work on 3.4-4.5V interval and 2A peak current. Read hardware doc carefully!

 

[vamsi.kodati]

sim300cz pin no

my sim vdd goes low after few seconds after powering up the sim 300. can any one pl reason it..

Added after 31 minutes:

thanks stephen. i have a doubt.
I am using 3.7 li ion battery for sim 300. if transmit burst occurs and sim 300 draws 2A current, won't the battery voltage drop below 3.4 due to high current drawn and is there any possibility of sim 300 shutting down

 

[GSM Man]

sim300 howto

The original post is 3 years old. YTou should have started a new thread.

Make sure you have a .22uF cap between the SIM_VDD pin and ground. Without it, the internal regulator shuts down.

 

[vamsi.kodati]

connect sim300 to telephone

i have a 0.1uf capacitor betweem sim vdd and ground. do i have to change to 0.22uf ..

Added after 2 minutes:

Oh thank you i put .1uf in the ckt and its working fine... Most of the time SIM300 detects simcard But at times say 1/10 times sim card is not being detected ie i get 2.85V at sim_vdd and then it drops to zero within few seconds but if it holds for 2.85V for few seconds it remains 2.85 n der r no probs. I couldnt debug y at times it doesnt work .

So when the simcard is placed and if SIM300 fails to detect the simcard ie after sim_vdd drops to 0 after how much time does SIM300 takes to retry detecting the simcard again??? Or only switching on/off SIM300 helps???

 

[GSM Man]

cms error : sm bl not ready

a .1uF is NOT large enough - you must use a .22uF.

The SIM_VDD voltage should not go to 0V - that indicates the regulator is shutting down.

Also, make sure you have a 10K pullup reistor between SIM_VDD and the Data line.

 

[pisoiu]

wavecom rts detected

I use 100nF and works well. Simcom documentation for SIM300, version 4.01, page 45 indicates a schematic with 100nF from SIM_VDD to GND.

/pisoiu

 

[vamsi.kodati]

sim300 power

Oh thank you!!! Btw i am planning to run SIM300 by 3.7V Li-ion battery. So is it possible to operate SIM300 with 3.7V Li-ion battery. To test it i powered my circuit by rps and kept checking the working of SIM300 and the netlight led glowed till 3.4V. But SIM300 starts responding awkwardly to AT commands below 3.68V. So does that mean that i hav to use a boost converter to 4.2 or 4.1V for better operation???

 

[pisoiu]

sim300cz v3.04 shematic

No, simcom modules are designed to work with a single cell Li-Ion or Li-Pol, without any converters. The module will respond to at commands at lower voltages, but when it will try to log on to gsm network, the voltage will, most probably, drop below minimum required voltage, and the module will shut down.
If modem respond incorrectly at 3.68V, which is not near empty battery, then you may have a problem elsewhere (cpu levels, etc.).

/pisoiu

 

[vamsi.kodati]

how to get better gsm reception sim300

Well i tried really hard to debug that prob. I hav interfaced it with atmega8 and kept sending AT commands via uart n then for debugging i connected the uart to comp in parallel. AT responses by sim300 was good till 3.68V and then it started responding awkwardly like the chars u get during baudrate prob. Moreover am using RPS(regulated power supply) unit for powering up my ckt n der r no probs with it. What could b the possible reason for this??? But the netlight glows till 3.4V

 

[GSM Man]

normal power down sim300

I use 100nF and works well. Simcom documentation for SIM300, version 4.01, page 45 indicates a schematic with 100nF from SIM_VDD to GND.
/pisoiu

I've never seen that version of the manual, but I sell about 200 boards a month with the SIM300/340 and I can tell you from experince that anything less than 220uF is not reliable for all modules. Some modules work with smaller caps on them, some are intermittent, and some don't work at all.

 

[vamsi.kodati]

detect sim presence in simcom

Well any solutions or reasons for y sim300 starts to create probs with AT commands at 3.6V???

 

[GSM Man]

sim300_v7 datasheet pdf

From the SIM300 Hardware Manual:

The power supply of SIM300 is from a single voltage source of VBAT= 3.4V...4.5V. In some case, the ripple in a transmit burst may cause voltage drops when current consumption rises to typical peaks of 2A, So the power supply must be able to provide sufficient current up to 2A.
For the VBAT input, a local bypass capacitor is recommended. A capacitor (about 100μF, low ESR) is recommended. Multi-layer ceramic chip (MLCC) capacitors can provide the best combination of low ESR and small size but may not be cost effective. A lower cost choice may be a 100 μF tantalum capacitor (low ESR) with a small (1 μF to 10μF) ceramic in parallel, which is illustrated as following figure. And the capacitors should put as closer as possible to the SIM300 VBAT pins.

Please pay special attention to the supply power when you are designing your applications. Please make sure that the input voltage will never drops below 3.4V even in a transmit burst during which the current consumption may rise up to 2A. If the power voltage drops below 3.4V, the module may be switched off. Using the board-to-board connector will be the best way to reduce the voltage drops. You should also take the resistance of the power supply lines on the host board or of battery pack into account.

It may be that the moudule is seeing spikes that drive the supply below 3.4V. My experience has been that the selection of bypass capacitors are critical. I've had problems if they are not good qaulity low-ESR ( < .2 ohm) tantalums.

 

[vamsi.kodati]

sim300 avrfreak schematics

Well i use RPS for my board right now and during transmit burst i saw current shooting upto 1.9A and my voltage was also constant and it didnt drop. Moreover sim300 didnt stop working or shut down at 3.6V but its not responding to AT commands properly even when sim300 is on at 3.6V...

 

[pisoiu]

pcb for sim300cz v3.04

Well i use RPS for my board right now and during transmit burst i saw current shooting upto 1.9A and my voltage was also constant and it didnt drop. Moreover sim300 didnt stop working or shut down at 3.6V but its not responding to AT commands properly even when sim300 is on at 3.6V...

Trust me, it's impossible to avoid voltage drops during GSM transmission bursts. But if you look for them with a multimeter, you won't see them. You need an oscilloscope for that.
Not responding to AT cmds is other issue, usually it has nothing to do with GSM transmitting pulses, since the high level on serial lines is around 2.8V, obtained from an internal regulator. It may have something to do with your cpu. A schematic would be helpful. How did you connect pc interface? You cannot connect it directly to modem, you need at least a polarity inverter and a level adapter. Logic 1 for serial line means 2.8V for Simcom interface and -15V for RS232 interface. Logic 0 means 0 for simcom and +15V for RS 232. Some RS232 interfaces works with 0/5V levels, but the signal still needs to be inverted.


/pisoiu

 

[vamsi.kodati]

download sim300 serial number

Well here am using atmega8 to send AT commands instead of comp. So i didnt connect serial port cable directly to sim300. I connected comp to my atmega8 via uart in parallel to sim300, to check if my avr transmits AT commands properly and avr echoes whatever it receives and thats how i am debugging my board. It works fine till 3.7 volts and then when i tried at 3.65V AT commands are sent properly to sim300 but its response goes awkward below 3.7V...