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On 22 Jun 2006 21:19:27 -0700, "kell" <kellrobinson@xxxxxxxxxxxx>
wrote:
>Chris W wrote:
>> I have a 2 way radio that will run with wide range of input
>> voltages(5V-16V). I mostly run it on batteries. Since in stand by mode
>> it draws very low current and will work with as little as 5V, it often
>> runs the NiCd/NIMh batteries down to too low of a voltage. Since I put
>> together my own battery packs, I was wondering if there was a way for me
>> to add a simple circuit that would just cut off the power when the
>> battery voltage dropped below some set point. The radio draws about 2
>> amps on high power transmit. Of course I don't want this circuit to
>> draw much additional current and preferable zero current once the shut
>> off point is reached. When in standby the radio only draws about 15 ma.
>> The set point would vary with the battery pack, some are 6 cell some
>> 8 and some 10. The set point will probably be 1.1V/cell
>>
>> --
>> Chris W
>> KE5GIX
>>
>try this (view in fixed font)
>
> p-channel
> mosfet
> s d
>bat------+--------- -----------+------load
>pos | |___| |
> | _ |
> 10K | |
> | | |
> | | ___/ zener
> '---------+ /_\ diode
> | |
> \c |
> npn |-----R-----'
> /e
> |
> gnd
>
---
What's going to turn on the MOSFET?
--
John Fields
Professional Circuit Designer
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