Low current draw relay

Using Arduino General Electronics
1

I have an Arduino project to control a few pumps that is running off battery power, and thanks to a lot of info on these forums I've been able to reduce the draw of my board considerably.

So now, when my board is not actively running it uses very little power. But I use a simple normally-closed relay to control my pumps, and these things use a fair amount power when in use. The pumps themselves are run off of a separate 6.5 volt battery source, so I'm not dealing with high voltage AC power.

I was hoping to get some suggestions on a low current draw alternative to my relay. Are there low power relays available? Or some other way to turn a pump off/ on other than a relay that would use less power?

2

If the pump battery negative and Arduino ground can be shared, then the pump can be switched almost lossless with a logic level mosfet.
Leo..

3

How about a line driver like ULN 2803a, which can trigger multiple devices.

4

Are there low power relays available?

Yes, very low ... check this dual-coil latching relay

Current Consumption Example:
Pump is switched on/off once per minute.
50ms pulse to set or reset the relay (28.1mA coil current).
Equivalent continuous coil current = (0.05/60)*28.1 = 23µA.
If pump is switched on/off once per hour ==> 0.38µA.
If pump is switched on/off once per day ==> 0.016µA.

A latching relay has memory ... contact state is unaffected by sleep mode or power on/off.

5

N-channel mosfets will work up to about 70A (for a 100A version if heatsunk propperly)
&versions up to 1000A :o

Here: 1.1A-~200A
Mouser.com mosfet search results

6

You can check out solid state relays: http://www.digikey.com/product-search/en/relays/solid-state-relays/1048664?k=solid%20state%20relay

7

sarouje:
How about a line driver like ULN 2803a, which can trigger multiple devices.

Not for a 6.5volt battery.
Darlington arrays like the ULNxxxx have a high saturation voltage.
There might be only 5volt left for the pump.

alexmg2:
You can check out solid state relays

A 30A/30mohm logic mosfet is $1.00
The same in SS relay is $75.00
Leo..

8

and thanks to a lot of info on these forums I've been able to reduce the draw of my board considerably.
So now, when my board is not actively running it uses very little power.

Sleep mode?

9

All really great ideas- thanks for the input.