5-10 years battery life of GPRS Water Meter, How?

[Ichan]

^ send me your sister's phone number, BTW...she's a cutie 

Male instinct? Surely i won't share it with you if i can get the number... LOL 

Anyway, while browsing about the disaster i found a picture (from Thailand) which is very inspiring on "flood proof vehicle" concept. 

-ichan

[Ichan]

I will assume that your minimum target quantity > 900 pieces (I always manufacture 10% extra for 1K Qty and 5% for more) and your target field service time is at least 3 years@50 degrees without altering (changing batteries). I will also assume that The GSM will send monthly consumption values and a malfunctioning massages (if any) as an SMS.  The SMS will contain Monitor S/N, date/time stamp for current reading, date/time stamp for the reading before, and current consumption. also need to know min2max L/min and pressure as well as tube diameter.

Please feed me back if my presumptions are correct.

Hi Faros, yes your presumptions is about right - in my case it will send the data at least once a day and the battery life only to be at least  2 year. After prototype the first order is 100 qty for field testing, if everybody happy than it will be several thousand in qty.

I still can not find a reason to use supercap, calculated the reservoir capacitor is only on thousands uF range - no need to go to Farad range. Polymer capacitor is choosen, very low esr and cheap nowadays as the large usage on motherboard and graphic card (known also as solid capacitor) - looks like it is even cheaper than tantalum.

I am going to do some experiment measuring the power profile of gprs module, aiming the elimination of voltage regulator for this metering device.

-ichan

[alexisnik]

That would be quite interesting, could you post the results back here after you have finished with the testing?

[Ichan]

That would be quite interesting, could you post the results back here after you have finished with the testing?

Okidoki, will do.

Won't be soon, need to buy the module first - Telit GL865 and U-Blox Leon G100.

-ichan.

[Faros]

@Ichan
I know it is country dependent situation however I believe there are two systems that uses remote billing:

1-Prepaid:
Where the client has GSM monitor/ controller (Bi-stable 3/4” solenoid or so) installed in his water supply, by charging the SIM card (same technique used for cellular phone), the client will have an amount of water available till he reaches the charged limits then the monitor switch off his water supply till the next charge.

2 -Postpaid:
Where the water monitor sends the monthly consumption to the water company billing system and the bill is issued to be paid later.

then, If your application requires the 1st application then it is a mandatory to have GSM/client and you should also consider the power required for the Bi-stable solenoid). OR

Your application is postpaid then you can use multipoint to single point RF (2.4GHz more or less) and have your monitors communicating with one controller for send/receive operation. This way you will be having one GSM/Building and as many as RF transmitter as your no. of clients. RF modules are widely available, cost effective and power effective as well while your GSM transmitter can be Battery backed up mains operating controller.

Regards,

[Ichan]

@Faros, sorry for being late on commenting.

My case is postpaid, the difficulties in developing prepaid system is on the "token generation" - it is beyond my scope.

I actually did a demo presentation for this project using MSP430 ez430-RF2500 development tool, the decision on using GPRS was made by the customer. I do interested to use low power RF polled to a base station and then send to the central station in any way. What low power RF module that you think appropriate for this? I think it will need to have several hundreds meter transmission range.

Anyway, I am now scratching my head for a simple thing: how to measure the battery voltage in a "low loss" way? Resistor dividers will draw some current in vain.. how large maximum value of resistor dividers feeding and adc?

-ichan

[Top]

Anyway, I am now scratching my head for a simple thing: how to measure the battery voltage in a "low loss" way? Resistor dividers will draw some current in vain.. how large maximum value of resistor dividers feeding and adc?

Just switch off the voltage divider with a MOSFET when not required.

http://www.microbuilder.eu/Tutorials/Fundamentals/MeasuringBatteryVoltage.aspx

[Ichan]

Thank for the link, good to know that.

I am a cheapskate  , two mosfet just for measuring the battery voltage is too extravagant for me...

Anyone, from three choice below - which one will work? which one you choose?

-ichan

[Ichan]

Another hard way to measure the battery, at 4.2V battery voltage the 10M resistor divider will took 42nA and datasheet said when the CS pin pulled high the op-amp will go to down to 50 nA - so the total will be below 0.1uA.

If the non CS op-amp variant used, it can be supplied by one GPIO.

-ichan

[solutions]

Why do you care what the battery voltage is? Seems silly and is major overkill to me.

{IF t=10 years} Change battery

Or measure, at the basestation, the received power, or BER, from the GSM sending unit. Its power output, or error rate, will degrade with battery voltage.

Done.

[Ichan]

Silly or not, i need to send it on each grps reporting.

-ichan