Re: MMf-EMf(VMf) two ways to cause a current.
- From: "Brian" <bellis350@xxxxxxxxxxx>
- Date: Sat, 28 Jan 2006 13:56:32 -0600
"Brian" <bellis350@xxxxxxxxxxx> wrote in message
news:9-ydnef5NqSOKEbeRVn-iA@xxxxxxxxxxxxxx
>
> "Xtrchessreal" <markgharrison@xxxxxxxxxxx> wrote in message
> news:1138420896.288876.217560@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>>
>> When designing a new electronic device you need to know the total
>> amount of power dissapation of the device especially if you intend to
>> build a DC power supply for the delicate circuitry within. The DC
>> power supply needs to be designed for the total dissapation and then
>> you need to also know the maximum current that can be supplied by the
>> power supply.
>
> You are approaching this in the wrong way. When designing a new electronic
> device (as far as the power is concerned), first you see what kind of
> voltage and current it needs to work. You then design the power supply to
> provide the voltage needed and the current needed. Using ohms law W = E I,
> you then know the wattage the power supply will be supplying.
As an example: If you tell me that you have a relay that will consume 8
watts to operate. That doesn't tell me much. But if you tell me that a relay
needs 8 volts at 1 amp to operate, that tells me what kind of power supply
it will need. Maybe I already have a power supply that I want to use, that
puts out 9 volts and can handle up to 2 amps. I could use a resistor in
series, to drop 1 volt at 1 amp. So using ohms law -- R = E/I and W = EI, we
would use a 1 ohm resistor that needs to be able to handle at least 1 watt.
If we didn't use the resistor in this example, the relay would overheat
because it will have more than 1 amp passing through it (because the voltage
is too high for it). The resistor is both reducing the voltage and current
to the relay.
Brian
.
- References:
- MMf-EMf(VMf) two ways to cause a current.
- From: Xtrchessreal
- Re: MMf-EMf(VMf) two ways to cause a current.
- From: Brian
- MMf-EMf(VMf) two ways to cause a current.
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