Low Current, Low Voltage Relay Needed

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

"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.

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.

Thanks much!

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?

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.

Good Luck

donald

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.

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.

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.

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

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.

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