Voltage Range GT864

15 thoughts on “Voltage Range GT864

  1. Hallo,


    I am using GT864 PY terminal. I read in datasheet and manuals that voltage range is 5-36 Vdc. I tested the module at 5 Vdc with a short original cable and a power supply of 4 Ampere Max Output.


    Module does not operates correctly using GPRS transmission. When I attach e.g. to an FTP module switch off during peak current trying to transmit.


    I repeated test using other antennas (directive high gain too) but no result even if condition of temperature, power supply and received signal are the best.


    I repeated test with new 5 modules and result was always the same, internal circuit does not stand this voltage. 


    Is there a part in the manual that specifies real voltage range of operation?


    Is there an extended range terminal that really operates at 5 V or is there a software possibility to reduce this problem? Why is declared to work 5-36 Vdc…?

    Is it possible that is a single problem of the terminals I have? 


    Thank You for any possible reply

  2. At 5 volts the terminal will draw some 2-3 hundreds of mA only so 4A is more than enough. However can you positively confirm your power supply capabilities? Can you monitor voltage and current to see what really happens?


  3. Dear Cosmin,


    I started these tests cause I had  problems even at higher voltages but I noticed that till 5.4 V this event is sure (with all the modules I have). 


    I can make more test but power supply is really good.


    It is a very big and professional regulated power supply (not switching). I regulated at max 4 Ampere to furnish max possible current during peaks.


    I cut also the furnished cable very very short to prevent any voltage loose there. 


    Then I also sometime added a 1000 uF at the end of cable near input.


    In the last final test I took just one module and I also bridged the internal protection diode….. (….this module is out of warranty now….) but no result.


    I started to think that reset input was not stable during peaks current, then I forced it to gnd but the problem was not it. 


     I can connect  a tecknotrics to measure any peak but power supply is really strong.


    Sequence is: power on, registration in the net, connection in GPRS, connection to a ftp  and shut down… till 5.4 V 100%…. 


     I tested many of 2 different dates of production but it works so.


    Thank You for any possible reply 

    1. Hi E. C. (why initials only, please put back the full name please, as they were before),


      What I had to say with positive confirmation, have a mean to check the actual voltage and current just before the terminal, no matter power supply specifications or label are saying. Problems can arise even in the best guarded places, you know, so worth a test to do …


        You are right,  I will test it again measuring directly the voltage then I will let You know.


        Thank You for support 

        1. I confirm You that voltage is more than 5 V and it doesnt show fluctuation.


          I monitored voltage by a tester, the display of the power supply unit and an oscilloscope.


          The terminal switch off always during transmission in GPRS.


          Thank You for any possible idea about this


          1. Hallo, 


            Amperometer shows about 200 mA then module switch off.  


            I tested also at 5.5 V with a series 0.1 Ohm to measure by an oscilloscope any peak but I didnt find any significant voltage/current peak.


            Thank You for any possible idea





          2. OK, thank you for the tests.


            I forgot to ask:

            – you are using internal TCP stack or as a modem for an external host?

            – how is your RJ11 connector wired, which lines?

            – how do you power ON and OFF

            – the terminal shuts down completely, confirmed by the middle green LED going OFF, or only stops communicating?

          3. Hallo,


            I am using internal TCP/IP stack (AT#GPRS AT#FTPOPEN and so on..)


            I am using line 1 VCC +5V, 3 HR_IN GND or floating, 4 TO_IN +5V, 6 GND GND


            I power on just supplying voltage with VCC and TO_IN together


            The terminal shuts down completely, just shows 6 mA with RS232 connected, if I detach 232 cable it is less than 1 mA.


            Thanks for support, I am not able to find my mistake cause I read HW manul carefully

          4. Hi Enrico,


            can you please post all the AT command sequence and when exactly the terminal shuts down?

            If I’ve correctly understood, you can get registered to GSM network and GPRS attach without problems. The problem is when you open the FTP socket, isn’t it?

            Did you also notice any shutdown during PDP context activation (AT#GPRS=1) ?


            Another good test would be to set AT#MSCLASS=8 instead of the default 10.

  4. Hi Andrea,


    GSM works always even in transmission.


    Problems start with GPRS. Rarely modem switch off when it is doing registration, sometime when it connects to GPRS and always when it makes an open or a put to server.


    Yes when You open ftp socket it switches off.


    Sequence is:


    -setting ….. parameters for connection, apn..

    – AT#GPRS=1

    – AT#FTPOPEN……and so on

    – AT #FTPPUT.. and so on


    I tried with AT#MSCLASS=8 ,  In this way it seems to work !!


    I continue to test but now it is the first time I see it is working at this voltage.


    Thank you very much for support


    1. I think the power consumed in class 8 is half of that in class 10. Why not try another power supply, even type of, just to not miss a chance?

      1. I need it still works perfectly near the lowest voltage in which a 6 V lead battery is not completely destroied that is about 5.3-5.5V. Even if it works slowly it is not a problem cause I transmit few data.


        Thank You