Very long battery life devices

[Michael]

There are battery operated radios (gas-meters, SCADA...) that are able to
get many years out of a battery. I'm guessing they usually sleep and wake
occasionally to transmit at full power using big capacitors. I need .75A
for .5 seconds, several times a day. How do I go about doing this?
(keeping the batteries (AA preferered) less than the size of a pack of
cards, no recharging)

 

[Fritz Schlunder]

"Michael" <Michael@yahoo.com> wrote in message
news:EirKd.32807$tD3.13135@fe37.usenetserver.com...

There are battery operated radios (gas-meters, SCADA...) that are able to
get many years out of a battery. I'm guessing they usually sleep and wake
occasionally to transmit at full power using big capacitors. I need .75A
for .5 seconds, several times a day. How do I go about doing this?
(keeping the batteries (AA preferered) less than the size of a pack of
cards, no recharging)

Uhh... AA alkaline batteries can supply 750mA for 0.5s several times a day
just fine. So what part are you having trouble with? It would be helpful
to know allot more about what you are doing and what your problem is. What
is your application, and what are the relevant voltages, etc.?

 

[Robert Monsen]

Michael wrote:

There are battery operated radios (gas-meters, SCADA...) that are able to
get many years out of a battery. I'm guessing they usually sleep and wake
occasionally to transmit at full power using big capacitors. I need .75A
for .5 seconds, several times a day. How do I go about doing this?
(keeping the batteries (AA preferered) less than the size of a pack of
cards, no recharging)

A microcontroller can do this. It can keep track of time, using minimal
power, and then wake up when required and enable your transmitter.

Some of these (the rfPIC series from microchip, for example) have
onboard transmitters that can be used to do the actual transmission,
given an antenna.

--
Regards,
Robert Monsen

"Your Highness, I have no need of this hypothesis."
- Pierre Laplace (1749-1827), to Napoleon,
on why his works on celestial mechanics make no mention of God.

 

[Michael]

"Fritz Schlunder" <me@privacy.net> wrote in message
news:35vi6eF4q7dekU1@individual.net...

"Michael" <Michael@yahoo.com> wrote in message
news:EirKd.32807$tD3.13135@fe37.usenetserver.com...
There are battery operated radios (gas-meters, SCADA...) that are able to
get many years out of a battery. I'm guessing they usually sleep and
wake
occasionally to transmit at full power using big capacitors. I need .75A
for .5 seconds, several times a day. How do I go about doing this?
(keeping the batteries (AA preferered) less than the size of a pack of
cards, no recharging)


Uhh... AA alkaline batteries can supply 750mA for 0.5s several times a
day
just fine. So what part are you having trouble with? It would be helpful
to know allot more about what you are doing and what your problem is.
What
is your application, and what are the relevant voltages, etc.?

3.3V. I tried 4-AA going to a 7805 and it choked. I don't think 8 (4x2)
would do the trick either. Do I need to charge a capacitor in order to
suplly the 'burst' needed? How?

 

[Jeroen]

"Michael" <Michael@yahoo.com> wrote in message
news:VDzKd.540$VC6.412@fe37.usenetserver.com...

"Fritz Schlunder" <me@privacy.net> wrote in message
news:35vi6eF4q7dekU1@individual.net...

"Michael" <Michael@yahoo.com> wrote in message
news:EirKd.32807$tD3.13135@fe37.usenetserver.com...
There are battery operated radios (gas-meters, SCADA...) that are able
to
get many years out of a battery. I'm guessing they usually sleep and
wake
occasionally to transmit at full power using big capacitors. I need
..75A
for .5 seconds, several times a day. How do I go about doing this?
(keeping the batteries (AA preferered) less than the size of a pack of
cards, no recharging)


Uhh... AA alkaline batteries can supply 750mA for 0.5s several times a
day
just fine. So what part are you having trouble with? It would be
helpful
to know allot more about what you are doing and what your problem is.
What
is your application, and what are the relevant voltages, etc.?


3.3V. I tried 4-AA going to a 7805 and it choked. I don't think 8 (4x2)
would do the trick either. Do I need to charge a capacitor in order to
suplly the 'burst' needed? How?

A 7805 uses 4 to 10mA of quiescent current already, so that's not the
regulator to use when you're after low power. Preferably you should not use
any regulator, but there are micropower regulators that don't use much power
for themselves.

Jeroen