Hi, and Welcome to Edaboard,
If you need to save power, consider usage of reed relays with magnets with NO state (reed relay is normally open, when door is open reed relay closes and give impuls to uC to send SMS on specified phone number).
GSM module needs more power to work then phone. Phone also have battery for working, which can give power to phone about five days - of course this depends from phone, but this phone will be only in standby state and will send sms only, that give more power to phone to prolong working time. Also GSM module have high price ranged from 30-50eur to 150eur and higher. GSM modules needs more power to works ranged from 200-300mA to 1A or even more.
If you plan to use PIR, smoke,... sensors you should see their need for power (about 20mA @12VDC).
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You need power, small solar cell can be out of room, put on light, and with cable that transmit power to device inside.
I am afraid that you dont have needed enough power and voltage from ~4AA.
With 4AA you get 6V (alkaline) or 4,8V (NiMi). I think this is low.
What does a Siemen phone use for Voltage? 7V/12V/14V?
Most of the PIR modules require 12V supply. If running off 4x AA's, you'd need a Charge-Pump to boost it up to 12V, but it might be really difficult to provide the kind of current needed for all this.
- Are you sure that GSM phone works well in your cellar ? If the signal strength is too low (feeble) then module will transmit at max. power, thus draw more current as well.
your passive monitoring, and activation using mechanical switch is a nice idea, but there are few things to keep in mind -
- time required by most uC's to startup ranges between 50-100ms (from power-on / reset)
- GSM modems will require the uC (once start up) to handshake, set up the AT-commands, etc., that too after the modem has registered to GSM network. The time it takes to do all that post a power-cycle can be in the order of several seconds.
- if you power-on all sensors, peripherals at the same time, immediately on startup, there would be a huge cold-start current draw, which your battery might find very hard to delivery, so you might want to space-out the sensor activation to overcome this.
given all the above, you'd see that passive sensors have the problem that they might actually miss critical events, especially if the events you are trying to detect, are momentary and happen too fast.
@JP few questions -
- Are you sure that GSM phone works well in your cellar ? If the signal strength is too low (feeble) then module will transmit at max. power, thus draw more current as well.
- Is there a possibility that you could separate out the "detection" unit and the "transmission" units, s.t. transmission unit is somewhere where possibility of grid-power, or other recurrently charging (s.a. using photovoltaics) exists ? That way, you can solve the power problem.
Unfortunately no. This alarm has to be 100% self powered.- Is there a possibility that you could separate out the "detection" unit and the "transmission" units, s.t. transmission unit is somewhere where possibility of grid-power, or other recurrently charging (s.a. using photovoltaics) exists ? That way, you can solve the power problem.
I was looking at this link **broken link removed** , which claims less than 10 microAmps! (how do thay do it?) With a batterysource of just 500mAh @3V this would power such a device for 500/0.01 = 50.000 hours?! Seems crazy to me...
Iterface for connecting SMS alarm to PC, only needed to use when programming SMS messages texts :
View attachment 70437
The same can be used to interface phone.
Siemens C65 can send AT commands, 100% its confirmed, I have that phone on one of SMS alarm.
See this AT command set for Siemens phones :
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