Tag Archives: gsm gate opener

Investigating GSM networks available to us using a CLX SIM

In the article we look at which GSM masts are available to us at our location and see which network will give us the best performance. We also look into establishing a data connection using the CLX SIM card and find the location of our PCB using QUECELL locate system.

We had a board hooked up with 2-way comms to a PC whilst developing the speech storage and playback function on our GSM Alarm Speech Dialler ADs (available at http://www.adventcontrols.co.uk).  We took this opportunity to investigate the network infrastructure we are able to acquire here in our office

GSM Dialler

GSM Speech Dialler with PC connection

Firstly, we send the command AT+CREG? which shows us that the modem is connected and roaming.  We are roaming as we are using the CLX SIM which has access to any GSM network in the UK.

AT+CREG?

+CREG: 0,5

 

Next, we send the AT+QOPS? command to get a list of masts the M66 is able to acquire:

AT+QOPS?

+QOPS: 1,”Vodafone”,”Voda UK”,”23415″

1,0062,305E,1A,22,94

+QOPS: 2,”O2″,”O2 -UK”,”23410″

1,53AC,9BDA,27,23,111       (n.b. 9BDA in hex is 39898 in decimal)

+QOPS: 1,”T-Mobile”,”EE”,”23430″

1,090A,9C47,1F,16,664

 

QOPS: 2 shows us we are currently using the O2-UK mast with location code 53AC and CellID 9BDA.  We can also see masts from T-Mobile (part of EE) and Vodafone are available to us (QOPS:1).  With the CellID we can find the mast we are using on a map

 

O2 Mast

GSM Mast Location

 

Earlier we were using an EE SIM, and this forced us to use a mast in the local retail park which is much further away and out of the screenshot above. This resulted in a signal strength of 16 as opposed to 23 from O2. This is the advantage of using the CLX SIM; it allows the modem to choose the most reliable network.

 

Another advantage of using the CLX SIM is that the GSM device will come with the APN set up correctly by default.  The Access Point Name (APN) tells the network which server your equipment can use. Networks will have different APN for different customers like PAYG or contract.  If you select the wrong one you will have no data access. This is the main cause of issues when using our software and emails. Our boards come with the APN settings for CLX pre-programmed which can be used globally.

 

To demonstrate data connectivity with the CLX SIM cards we will make use of Quectel’s Cellular Positioning System.  This will give is the geographic co-ordinates of the PCB even when indoors.  The modem connects, through the internet, to Quectel’s database of GSM masts and then compares the signal strength from each mast to locate the device.

 

Firstly we must tell the modem the APN which will give us access to the internet as follows:

 

at+qicsgp=1,”connect”,””,””                   …the CLX APN is “connect” with no username or password

at+qcellloc=1                                                     …enquire about our current location

+QCELLLOC: -2.861663,53.353088

 

The at+qcellloc command returns our co-ordinates which we can then paste into Google Maps

QUECLOCATE

Using Cellular Location

The position given by the Quec Locate server is about 0.5 miles out with our high gain antenna.  This is towards a worst case scenario situation given that our PCB is buried deep within a building.  If it were outside it would be much more accurate.

We tried again using the internal adhesive antenna we use for our Gold:Mini Intercom and this time the error was about 0.8 miles.  This is because the internal antenna is optimised for 1800MHz masts which are predominantly located in this direction.

+QCELLLOC: -2.863965,53.361809

GSM ALARM LOCATOR

Low gain antenna location attempt

 

To view our GSM products and for live demonstrations please visit our stand at IFSEC 2018.  We look forward to meeting you.

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Gold Mini GSM Intercom: production, testing, inspection

Finally we saw our new Mini Intercom enter production.  It uses a new and novel manufacturing technique which required several iterations to get right.  The end result is a solid, strong lump of fiber glass with a pretty black and gold finish – and yes that’s real gold!  At just 4mm thick this intercom has the appearance of a flush mounted unit but is in fact surface mounted; a common trait for all our Gold intercoms.

4mm thick intercom

Side view

The intercom is fully waterproof. We use the gold finish as it is non-corrosive.  The three parts of the intercom are brazed together forming a water tight seal around the unit rather like a copper pipe is soldered to form a seal.

soldering joint x-ray

Solder seal x-ray

After the soldering process we inspect the intercom using an x-ray to ensure the seal has been formed around the entire perimeter of the unit.

QFN x-ray

Processor soldering inspection

May 16 Update Video: Dialler PCBs, Gold Intercom and PC Software

Video Timing

  • New Roller Shutter PCB (2-in 2-out PCB) 0:20s [C4 Webpage ]
  • D4 Analogue Voltage Measurement and 6 input PCB 0:36s [D4 Webpage]
  • D4 PCB also PCB tested in software 3:20s [D4 Webpage]
  • G2 GSM Intercom 0:55s [GSM Intercoms]
  • New A4 PCB 1:55s [2-Input GSM Dialler]
  • PC Control Software 4:40s [PC Software Download]

In the video we mainly demonstrate the PC software.  This connects via the internet to your PCB and allows you to view settings and numbers as well as monitor the system live.  The PC software in on the whole done we’re waiting for our server software to be complete.

PAYG SIM Card Deactivation

When using Pay As You Go (PAYG) SIM cards in equipment such as dialers and gate openers you should be aware that the network may chose to deactivate your SIM card should you not meet the minimum usage requirements.  In the UK the strictest networks require at least a call or text message to be sent once per quarter – Lebara Mobile require 1 call/SMS per 3 28 day calendar months.

For details of the terms and conditions for each network I recommend following this link with an excellent article written on the subject:

http://kenstechtips.com/index.php/payg-inactivity-account-termination-and-credit-expiry

Further details can be found here on the basis for these policies:

https://community.giffgaff.com/t5/Blog/Recycling-mobile-numbers-giffgaff/ba-p/8211666

Our GSM equipment has two SIM card Keep Alive functions which automatically send an SMS or dial a number to keep your SIM card within the terms and conditions of the network.  All products have the Keep Alive Text feature which sends an automated SMS message at user specified intervals to their chosen number.  This is set up as follows:

KAT 07000000000,28.       Sends a keep alive message every 28 days to 07000000000

Dialers and Gate Openers with firmware version 3.18 or later additionally have the ability to dial numbers where a voice call is a requirement.  This is set up using the following command:

KAC 01512834306,80.      Dials 01512834306 every 80 days

Should the call go unanswered it unit will retry 4 times and will then send an SMS to the first master number with the following text ‘KAC@Fail’.  In this case a manual call should be made with the following command:

Dial 01512834306.     …or the number of your choice

Where your network requires a call to be made but your device has firmware prior to F3.18 we recommend setting the Keep Alive Text message to remind you to make a manual call for your required interval using the dial command.  Ensure the call is answered.

Gold G2 GSM Intercom Door Entry Phone Update

January has proven to be a busy month with many trade and online orders for our ever popular GSM Auto Dialer system (GSM Dialer).  We’ve also taken on a new member of staff, Kelly, to handle orders for this product.  Hopefully for her sake the next couple of weeks will be a little quieter!  It would also allow further progress on our new Gold series of intercoms.

GSM for AndrewWe have been installing the first of our Gold Series GSM Door Phone Intercoms which is the Gold G2 Model.  However they are still in short supply and we’re still working on the firmware.

The early versions have been using the Capacitive Sensing Module on-board the PIC microcontroller.  This has proven highly reliable and accurate in the field however in theory this module is susceptible to electrical interference.

CSM Scope View

CSM Pad Trace

The CSM module generates a frequency dependent on the capacitance applied to the pin of the chip.  However it is possible for the touch pad to pick up high strength electrical noise and start oscillating at the frequency of the noise.  This would be seen as a press even though nobody touched it.  In practice we have not seen this but we also developed an alternative software based decoder which measures the voltage on the touch pad after it has been discharge and charged by the Analogue to Digital Convertor (ADC) sampling capacitor.

CVD Touch Pad Trace

CVD Touch Pad Trace

This technique of measuring the pad charge and then discharge into the same capacitor is known as a Capacitive Voltage Divider (CVD).  This method is very resilient to noise and electrical interference but does require more CPU processing time.  It is likely to be implemented across all of our Gold GSM Intercoms and will soon be behind the touch pads of our G2 unit.  When we have a full keypad version of the intercom available it will be important to use this technique hence it is being developed now.

GSM Dialer/Gate Opener Current Consumption Question

Hi there,
How many milliamps does it need from the alarm board to run?

(no name supplied)

GSM Dialer Current at various voltages

GSM Dialer Current Graph

As can be seen from the graph the current consumption drops with increasing supply voltage.  The is due to the use of an efficient Switch Mode Power Supply (SMPS) buck regulator on board which converts a high voltage at low current to the low voltage and high current required by the GSM transmitter chipset.  The GSM system requires up to 2 Amps at 3.6v.  However, due to the SMPS at 28v the current requirements during transmission are as low as 60mA average.  This can also be explained due to the 12.5% duty cycle used during GSM TDMA transmissions.  GSM transmits only in short powerful bursts with a 1/8th duty cycle.

The system’s electrical energy requirement every second (by definition this is know as Power) is the same whether the PCB is supplied by 12v, 18v or 28v.  Power consumption can be calculated for DC loads using the following formula:

Power  = Voltage x Current  normally written  P = VI

The inverse current plot is expected when we re-arrange the formula as follows:

I = P/V

As the power requirement, P, is constant no matter what voltage we supply we see as the voltage, V, is increased I, the current, must be reduced.

GSM Dialer power requirement

GSM Dialer Power Consumption

The above graph showing power consumption at various voltages shows the most efficient supply voltage is approximately 12v particularly when idling.

Please note these figures were obtained on the 1800MHz band (EE network) with a low RSSI of 10.  They were obtained during the higher power ringing phase and would drop during talk-time.  Transmission at 900MHz (O2 network) may give higher current consumption due to the higher power output of the transmitter but may also be lower if the signal strength is superior.
Here is the measured current consumption at various DC voltages:

28V
20mA idle
60mA during call (peak 70mA with relay on)
18v
26mA idle
95mA call (115ma Relay)
14v
30mA Idle
110mA (145mA Relay)
12v
34mA
127mA (160mA Relay)

Regards,

Michael

The GSM Alarm Dialer and SMS sender is available from the Advent Controls website using the following link:

http://www.adventcontrols.co.uk/gsm-auto-dialer.html

GSM Dialer Connection to a PIR Detector and use as a GSM Gate Opener

Hi, can I check how I would wire up a standalone PIR to this to activate the dialler (seperate to the alarm panel)? Also out of curiosity the output controls on this autodialer are they the same as the GSM gate opener board (ie so can be used to open gates too)? Many thanks.

GSM Dialer

Advent Controls GSM Dialer and Gate Opener

Hi,

You can wire the PIR output directly to the GND and input terminal (A or B).  The dialer expects and Normally Open (NO) type of signal so it send messages when the equipment closes it’s output contacts.  With a PIR, however, the output is Normally Closed (NC).  So you just need to tell the dialer to trigger when the input goes open as follows:

inlevel open

The gate opener and dialer are the same product except people use the inputs on the dialer and outputs on the gate opener.  It is perfectly OK to use both the inputs and outputs at the same time and hence use the same board as a dialer and a gate opener.

Thanks,

Advent Controls

GSM Dialer Link

GSM Gate Opener Link