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'Looking for low power consumption switch (way) tha'
2008\08\13@210447 by Apptech

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> I need to turn on and off a load that takes very little
> power (a few ma at 3V). I want all the power I supply to
> the circuit goes mostly to the load itself but not the
> switching device. I couldn't use a relay since the relay
> coil consumes too much power. I don't even want to use a
> transistor as a switch, because when it is saturated,
> there is a certain volt-drop across it, hence some power
> is lost in the transistor. Is there any component (or
> methods) that could be used as a switch and at the same
> time the power loss in the switch itself is very low?


More information would help BUT
A MOSFET will very probably do what you want.
FDN337 or FDN338 are a good start depending on whether you
want a low side or a high side switch.
See eg  http://www.digikey.com

Power consumption off or on is about zero.
Voltage drop when on is about zero.


       Russell McMahon

2008\08\14@064422 by olin piclist

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John Waters wrote:
> I need to turn on and off a load that takes very little power (a few
> ma at 3V). I want all the power I supply to the circuit goes mostly
> to the load itself but not the switching device. I couldn't use a
> relay since the relay coil consumes too much power. I

Look up "transistor".  Both bipolar and FET could be appropriate depending
on details.  You also need to decide whether you can switch the high side,
low side, or either.  All else being equal, it's ususally easier to switch
the low side.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\08\19@215619 by Martin K

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Olin Lathrop wrote:
> John Waters wrote:
>  
>> I need to turn on and off a load that takes very little power (a few
>> ma at 3V). I want all the power I supply to the circuit goes mostly
>> to the load itself but not the switching device. I couldn't use a
>> relay since the relay coil consumes too much power. I
>>    
>
> Look up "transistor".  Both bipolar and FET could be appropriate depending
> on details.  You also need to decide whether you can switch the high side,
> low side, or either.  All else being equal, it's ususally easier to switch
> the low side.
>
>
> ********************************************************************
> Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
> (978) 742-9014.  Gold level PIC consultants since 2000.
>  
Usually easier, but at 3v-3mA a PMOS is going to work well. The FDV302P
having an Rds of about 12 ohms would drop about 36mV.

-
Martin

2008\08\20@020809 by Mongol Herdsman

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>> I need to turn on and off a load that takes very little
>> power (a few ma at 3V). I want all the power I supply to
>> the circuit goes mostly to the load itself but not the
>> switching device. I couldn't use a relay since the relay
>> coil consumes too much power.

Use latching relay like this one:
www.maplin.co.uk/module.aspx?ModuleNo=37529&doy=search

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