[Lab] AC adapter question

[Michael Grant]

Ah, I used 1v2, was thinking about optocouplers...
You still want to de-rate your resistors significantly, 3 or 4 times is
normal..

Michael




On Thu, Jul 11, 2013 at 9:20 PM, Andrew O'Malley <aomalley at gmail.com> wrote:

> The 7 amp calculation is correct.  Try to find a 5V @ 10A supply and you
> should be good, assuming the circuit is as you described.  The one you
> linked to is 26A which is a bit overkill (though nothing wrong w/ using it,
> it will only supply the amount of current required by the circuit).
>
>
> >>> Maybe I'm drawing too much Amps.  Would you recommend this AC converter
>
>> >>> over the last one:
>> >>> http://www.digikey.ca/product-detail/en/LS150-5/285-1817-ND/1918828
>> >>>
>> >>> I would have Amps to spare on this one.
>>
>
>
>
>> Your LEDs have a forward voltage of 1.6 volts and you are supplying 5
>>
>> volts,  leaving 3.4 volts for the 91 ohm resistor. Ohms law: current =
>> volts / resistance. Plug in the numbers and you get 0.037 amps per LED,
>> much less than the 0.250 amps that the resistors are rated for. The total
>> current would be 7 amps, which is more than your supply is rated for.
>>
>
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