Low Current, Low Voltage Relay Needed

[[email protected]]

I need a DPST relay (reed perhaps is best) with the very lowest current
and voltage requirements for operation. But not a surface mount device.
This is for a battery operated device that must operate at 8 hours
continuously per day, switching outputs every 15 minutes. The current
and voltage flow out will be unmeasurably low, perhaps picoamps and
picovolts or even less. Thanks much for your time in replying. Btw, it
wouldn't hurt if it cost less than $2, if such a thing exists.

 

[Sjouke Burry]

I need a DPST relay (reed perhaps is best) with the very lowest current
and voltage requirements for operation. But not a surface mount device.
This is for a battery operated device that must operate at 8 hours
continuously per day, switching outputs every 15 minutes. The current
and voltage flow out will be unmeasurably low, perhaps picoamps and
picovolts or even less. Thanks much for your time in replying. Btw, it
wouldn't hurt if it cost less than $2, if such a thing exists.

I would search for a bistable (micro)switch,you only need to
pulse that,to switch it around,and it will not consume anything
in between.

 

[[email protected]]

Thanks! Can it be controlled as so in this circuit?

http://www.audiopulse.net/15_minute_timer.jpg

 

[gcd]

Hi,
I agree with the above post, use a latching relay only, need to pulse it
when change overs are required.

Also note a few things about relays:
1) They do have specifications for minimum currents. You can end up with
higher resistance contacts otherwise
2) Given your application you will need to pay careful attention to the
contact materials otherwise you will end up with dissimialr metals (galvanic
action with humidity), thermocouple action and if there are oxides present
on the contacts you will end up with diode activity.
3) leakage resistance between open and closed contacts, given the
application - this may be important

The above are important given the context of picoamps and or picovolts.
Perhaps I've misunderstood the application? Perhaps a relay isnt what you're
after?

Greg

 

[Sjouke Burry]

Thanks! Can it be controlled as so in this circuit?

http://www.audiopulse.net/15_minute_timer.jpg

I googled for "bistable reed relay",and if you have some
5 V or higher around,there are several on google that can
do your job, some have 2 coils, in others you have to change
the direction or the coil current.

 

[[email protected]]

"The above are important given the context of picoamps and or
picovolts.
Perhaps I've misunderstood the application? Perhaps a relay isnt what
you're
after?"

The output will never be measured or used, but it needs to be switched
every 15 minutes. I had thought a reed relay might be the thing, lower
current drain than a regular solenoid.

 

[[email protected]]

I googled for "bistable reed relay",and if you have some
5 V or higher around,there are several on google that can
do your job, some have 2 coils, in others you have to change
the direction or the coil current.

Thanks! How long do you think a regular 9V battery could power such a
circuit, with the timer schematic I linked to? I know it would involve
crunching a lot of numbers, but just your intuition would do.

 

[Sjouke Burry]

Thanks! How long do you think a regular 9V battery could power such a
circuit, with the timer schematic I linked to? I know it would involve
crunching a lot of numbers, but just your intuition would do.

For a bistable reed, it does not consume anything, only
when you pulse it to the other state,it draws current for
5 or 10 millisecond,with a resistance of 200 ohms or more,
so for the lifetime of your battery you can ignore that.
Sorry ,12.30, I'm off to sleep.

 

[[email protected]]

Thanks much!

 

[Walter Harley]

"The above are important given the context of picoamps and or
picovolts.
Perhaps I've misunderstood the application? Perhaps a relay isnt what
you're
after?"

The output will never be measured or used, but it needs to be switched
every 15 minutes. I had thought a reed relay might be the thing, lower
current drain than a regular solenoid.

Can you be a hair less cryptic? Folks here might be able to help you a lot
more.

If the output is picovolts or picoamps (and which is it, by the way?), and
it's never going to be "measured or used", why bother with it at all?

 

[Donald]

Thanks! How long do you think a regular 9V battery could power such a
circuit, with the timer schematic I linked to? I know it would involve

No, the coils need to be pulsed. About 100 mSec to CLOSE the contacts
and 100 mSec to OPEN the contacts.

No current for 29.9 seconds per cycle.

Your schematic powers the 2n3904 for 15 minutes, then powers it down for
15 minutes.

Triggering a one-shot that times 100 mSec.

Two 555 timers, one for CLOSE and one for OPEN.

crunching a lot of numbers, but just your intuition would do.

Good Luck

donald

 

[Fred Bloggs]

"The above are important given the context of picoamps and or
picovolts.
Perhaps I've misunderstood the application? Perhaps a relay isnt what
you're
after?"

The output will never be measured or used, but it needs to be switched
every 15 minutes. I had thought a reed relay might be the thing, lower
current drain than a regular solenoid.

If the relay output will never be measured or used then the only thing
you might want out of it is the magnetic field- disregarding the
possibility of a barely audible click or some other kind of nutcase
effect. How much field do you need and at what distance, what is
detecting it? As for your circuit, the 400 ohm relay draws about 10mA on
average at 8.2V and the 4060, which should be oscillating at
2^14*1/(30*60)=9Hz, draws nothing. And you can increase the 3904 base
drive resistor to 10K. The standard alkaline 9V is ~600mAH so that you
should get over 60 hours of operation as long as the temperature remains
around 70oF. But that is just to activate the relay- the circuit will
continue to produce a pulsed magnetic field whether or not the relay
actuates. So the battery may be usable for much longer than 60 hours
depending upon your sensor.

 

[ehsjr]

No, the coils need to be pulsed. About 100 mSec to CLOSE the contacts
and 100 mSec to OPEN the contacts.

Less than 1/10 that. Under 10 mS.
Ed