piclist 1999\03\08\191352a >
Thread: Solar Panels? - Why PWM Works
www.piclist.com/techref/io/pwm/index.htm?key=pwm
face picon face BY : Sean Breheny email (remove spam text)



Hi John,

At 05:40 PM 3/8/99 -0600, you wrote:
[SNIP]
>|Won't you actually achieve max. power transfer to the cap when the product
>|of the voltage across it and the current thru it is maximum? This won't
>|occur when you first hook it up because the voltage across the cap is
>|initially zero,so the power transfered is initially zero.
>
[SNIP]
>Suppose, however, that you have a device powered by a "9 volt"
>battery which needs to drive a 100-ohm solenoid for 100ms with
>at least 60mA.  If you have a 4,700uF cap in parallel with the
>battery it will be able to supply that demand while dropping
>less than two volts even if the battery is not in good shape and
>has an internal resistance of 100 ohms (in which case connecting
>a 100ohm load without the cap would cause the voltage to drop by
>half, failing to meet the 60mA requirement).
>

I see,I misunderstood the original post,then,I should have followed the
thread more closely. I thought that the original post was talking about
simply using a battery to charge a cap,nothing else,and was saying that the
power delivered to the cap was greatest when the cap was discharged
completely.

Thanks,

Sean

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
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In reply to: <01BE698A.135678B0@JOHN_WKST1>
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