Tag Archives: gsm switch

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:

20mA idle
60mA during call (peak 70mA with relay on)
26mA idle
95mA call (115ma Relay)
30mA Idle
110mA (145mA Relay)
127mA (160mA Relay)



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



Do we want nano SIMs?


Initial Design Layout for B3.01

We’re currently re-designing the twin output relay board which up to now has had no input.  It’s also a pretty old design (>2 years which is amazingly geriatric in the GSM industry) so is well in need of updating.  It’s tempting to go quite radical as we could add Bluetooth quite easily for number setup but that may have to wait.

What we would love to know is whether you as an installer want to see a nano SIM holder yet.  The larger micro SIM is becoming less common and I frequently find callers to the office have no means of fitting the dialer/gate opener SIM in their own mobile for registering/testing.  Do you want to see our products with a nano SIM holder?

GSM Gate Opener A3.02

Advent Controls A3.02

It is likely, as these boards have some crossover in terms of application, we will put the nano SIM on this board and the full size SIM on the 1-out 2-in board and see which users prefer.

Please leave your thoughts in the comments they would be very much appreciated! (click leave a reply at the top)

GSM Roller Shutter Controller Link

GSM Gate Opener Link

Disallowing some users access to the relay on the GSM Dialer and Gate Opener

We had a user question which required a unusual solution so I thought this is ideal for the blog.  Quite crafty I’d say!


Another question for you. The relay can be activated with a call. Is there any way of setting the numbers that can do this. I don’t want all the text numbers to be able to use the relay. See I have set this up as a back up to a pager system. Should it fail I only want 3 numbers only to be able to set it off the relay. Thanks again for your time and help

GSM Switch

GSM Switch with Volt-Free Relay Output


I had to have a little think about this one. The easy answer is no. All numbers can operate the relay. What you can do though it add an extra digit to the end of the phone number you don’t want allowed. When the dialer searches the memory it looks at the last 8 digits of the number you gave it. If I did this with my number:

Actual: 07574163367

Given to dialer: 075741633670 (added a 0)

The dialer would get 07574163367 from the network but when it looks in its memory it will only see 41633670 which will not be a match so it will not allow the relay to be operated. However, when it sends messages or dials the number you have given it, it will add the extra 0 but the network will know this is too long and ignore it. Try the SIM in your mobile and see if it does actually call/send messages with the extra character. Mine does and I use an EE SIM.

So for those you want to access the relay put the number in correctly and for those you don’t add the character.


Advent Controls

GSM Dialer Link

GSM Gate Opener Link

GSM Dialer and Gate Opener Out of Stock

Unfortunately due to high demand recently we have again sold out of the A3.02 dialer and relay board.  Although we expected the latest batch to have been assembled by now we also ran into a supply chain issue with a component we only use on this product (the AP5004SG-13 buck regulator if you’re interested!).  The stock we thought was there in our distributor’s warehouse wasn’t.

GSM Switch

GSM Switch with Volt-Free Relay Output

We’ve managed to secure a supply of the chips due to land on Friday 10th of October and our assembler is able to build the PCBs as soon as they arrive so we should have a good supply of the board at some point mid-week next week.  Currently we expect this to be Wednesday 15th of October and expect them to still be warm having just come out of the reflow oven!

Sorry for any inconvenience this has caused.  Hopefully the period of no stock will be as short as possible.

Michael Beaver


Advent Controls

Troubleshooting Setup Issues for Advent Controls GSM Dialers and Relay Boards

Michael describes the most common problems users have when first setting up the GSM systems.

The installer should set up a master user number (their own phone number) before attempting anything else. However sometimes, if there is a SIM fault or aerial problem, the system will not be ready for this. The video describes the symptoms and how to resolve them.

Of course if any further help is needed please feel free to get in touch with Advent Controls