Russell McMahon wrote:
>> The modems are a few hundred
>> dollars (1-off) and only draw about 10mA when idle, which is not too bad
>> I guess.
>>     
>
> 10 mA = 240 mAh/day ~= 1.7 Ah/week.
>
> Present current usage is about 2 AH / week based on your initial
> figures, so IF the modems were always on they would come close to
> doubling your present energy use. It's annoying how such things add up
> :-(.
>
> Polling occasionally with the modem usually in sleep mode could reduce
> this substantially. Depends on wakeup time and acceptable latency for
> a command response.
>   

Yes, it does all add up.  I can power the GSM modem down completely 
until required. He only really needs it for one way reporting of faults 
and status.  The comment on current was more of a "by the way" remark 
for general info. The SMS (fault / status) reporting is a separate 
function to the remote control.  Sorry about the confusion.

A low cost RF transceiver module (for the 20m range remote) may still 
draw a few mA in receive mode.

> Seeing if the motor energy use could be reduced may also pay dividends.
>   

I'm yet to see the motor and make some measurements.  The battery life 
(according to the client) seems to be much the same whether the machines 
activates 3 or 30 times a day.

I don't know what Ah rating the battery.  It is marked as 12V, 175 CCA 
so it's possibly a motorcycle type.  Some investigation is required.

> Your carefully vague [tm] description doesn't note whether it's
> indoors or out, but the 20 metre range suggests that it MAY be
> outdoors.

Vague [tm]? Me? You know how it goes sometimes when you don't know who 
else is listening. :-D

The application is indoors.  The lack of mains power is more to do with 
installation problems and trip hazard caused by trailing cables.  Think 
of the motor as dispensing items.
David...

-- 
___________________________________________
David Duffy        Audio Visual Devices P/L
Unit 8, 10 Hook St, Capalaba 4157 Australia
Ph: +61 7 38235717      Fax: +61 7 38234717
Our Web Site: www.audiovisualdevices.com.au
___________________________________________

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