Chris wrote:
> On Jun 26, 8:04 pm, lili...@[EMAIL PROTECTED]
wrote:
>
>>On Jun 26, 6:23 pm, Peter Bennett <pete...@[EMAIL PROTECTED]
> wrote:
>>
>>
>>
>>
>>
>>
>>>On Thu, 26 Jun 2008 14:09:18 -0700 (PDT), lili...@[EMAIL PROTECTED]
wrote:
>>>
>>>>On Jun 26, 4:43 pm, mrdarr...@[EMAIL PROTECTED]
wrote:
>>>>
>>>>>On Jun 26, 1:16 pm, lili...@[EMAIL PROTECTED]
wrote:
>>
>>>>>>On Jun 26, 4:10 pm, mrdarr...@[EMAIL PROTECTED]
wrote:
>>
>>>>>>>On Jun 26, 12:20 pm, lili...@[EMAIL PROTECTED]
wrote:
>>
>>>>>>>>Hello everybody,
>>
>>>>>>>>I have a set of battery, but I only one hooked up to the circuit,
The
>>>>>>>>other one act as a backup. I want to implement an electronic unit
that
>>>>>>>>will change (swap) the batteries.Therefore the wiring will need to
be
>>>>>>>>changed. The circuit need to sup****t 5amp of continuous current.
Here
>>>>>>>>is what I want to implement.
>>>>>>>>from:
>>>>>>>>A to C
>>>>>>>>B to D
>>
>>>>>>>>to:
>>>>>>>>A to D
>>>>>>>>B to C
>>
>>>>>>>>Is it better to use a analogue or digital switching approach. I am
>>>>>>>>just worried that digital might take too much energy by keeping
those
>>>>>>>>transistor or mosfet open and close.
>>
>>>>>>>>Li
>>
>>>>>>>You mean something like this? (view in fixed-width font, for
example,
>>>>>>>with Notepad)
>>
>>>>>>>+---+ +----+ +---+
>>>>>>>|(+)|--switch A--| |--switch C--|(+)|
>>>>>>>| | |Load| | |
>>>>>>>| | | | | |
>>>>>>>|(-)|--switch B--| |--switch D--| |
>>>>>>>+---- +----+ +---+
>>
>>>>>>>Batt 1 Batt 2
>>
>>>>>>Michael, This is basically what I want to do.
>>>>>>The battery will run a very small motor and a light.
>>
>>>>>>Li
>>
>>>>>Looks like a double-pole-double-throw switch will work
>>
>>>>>see http://en.wikipedia.org/wiki/Switch
>>>>>look under DPDT
>>
>>>>>seems simpler than a MOSFET solution.
>>
>>>>>When exactly do you want to switch?
>>
>>>>>Michael
>>
>>>>This was one of the initial idea, Maybe have a servo motor to control
>>>>the switch. ( and a PIC chip to supervise the whole operation)
>>>>K
>>
>>>Use a relay - that's an electrically controlled switch.
>>
>>>There is probably no need to switch both positive and negative
>>>terminals - using an SPDT switch in the positive leads would likely be
>>>sufficient.
>>
>>>An output of a PIC probably won't drive a 5 amp relay directly, so you
>>>would have to have the PIC drive a transistor or small relay, which
>>>would drive the large relay.
>>
>>>--
>>>Peter Bennett, VE7CEI
>>>peterbb4 (at) interchange.ubc.ca
>>>GPS and NMEA info:http://vancouver-webpages.com/peter
>>>Vancouver Power Squadron:http://vancouver.powersquadron.ca
>>
>>would there be anything else beside a relay?
>>that would require energy only when switching is required?
>>
>>Li- Hide quoted text -
>>
>>- Show quoted text -
>
>
> Try looking up a "latching relay". They only require power when
> they're switching. Driving a 5A load is going to require a realy with
> at least a 1 watt coil, so you'll need two transistors to drive the
> two coils from the PIC.
>
> Cheers
> Chris
Actually, there are a number of relays that require well
under 1 watt for the coil that can handle a 5A load.
Digikey, Mouser, Newark - the usual suspects - all
carry them. For example, Mouser part# 653-G2RL-24-DC12 is
a DPDT relay with a 12V 33.33 mA (~.4 watts) coil, and has
contacts rated 8 amps at 30 VDC. Even Allelectronics
carries a few that handle 5 amps at the contacts and
need well under a watt for the coil.
Ed
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