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Science Forum Index » Electronics - Basics Forum » Baisc resistor, electricity, and capacitor questions
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| ehsjr |
 Posted: Sat Feb 10, 2007 4:15 pm |
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Guest
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Robin wrote:
(much snipped)
Quote:
Your Capacitor is too small.
Quite possible - he didn't mention the cap size.
I figure he needs at least 2.2 uF to get a readily
visible blink. He could charge it to say 6 volts,
then discharge it through the LED and a 1K resistor.
Nice.
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| MassiveProng |
| Posted: Sat Feb 10, 2007 4:32 pm |
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On Wed, 07 Feb 2007 10:42:43 -0500, John Popelish <jpopelish@rica.net>
Gave us:
Quote:
Resistors resist the passage of current by using up voltage.
Remember that ohms (the unit of resistance is just a
shorthand way to say volts per ampere. 10 ohms of
resistance uses up (drops) 10 volts per ampere that passes
through.
Excellent method of defining Ohm's Law in yet one more
understandable way. |
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| Jamie |
| Posted: Sat Feb 10, 2007 4:45 pm |
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MassiveProng wrote:
Quote: On Wed, 07 Feb 2007 10:42:43 -0500, John Popelish <jpopelish@rica.net
Gave us:
Resistors resist the passage of current by using up voltage.
Remember that ohms (the unit of resistance is just a
shorthand way to say volts per ampere. 10 ohms of
resistance uses up (drops) 10 volts per ampere that passes
through.
Excellent method of defining Ohm's Law in yet one more
understandable way.
I just wanted to say, interesting name you have Mr MassiveProng.
You are referring to components of a plug correct?, i just
can't for the life of me think of it being anything else!
--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5 |
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| Peter Bennett |
| Posted: Sat Feb 10, 2007 10:51 pm |
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On 7 Feb 2007 06:33:50 -0800, "electronman" <zken@tongaken.org> wrote:
Quote: After you read my questions, you will understand why I joined this
basic electronics group.
snip
3) I thought the purpose of a capacitor was to hold a charge for a
brief instance, then release it. So when I connect a resistor then
capacitor then LED in series with a 9V battery, why doesn't the LED
blink on and off as the capacitor charges and releases?
Thanks in advance for your help.
A capacitor does not "hold a charge then release it" as you seem to
expect.
I suggest that you consider a capacitor as a (very small) rechargeable
battery - when you apply a voltage to a capacitor, it will charge up
to that voltage, and retain that charge. If you disconnect the
charging voltage and connect a load (resistor and LED, of example) the
capacitor will discharge through that load. With a suitable voltage
and a large enough capacitor, the LED will blink once. You would have
to recharge the capacitor, then connect the load again to see the LED
blink again.
To make the LED blink on and off, you need some active devices -
transistors or an IC - in a suitable circuit to switch the LED current
on and off. Part of the circuit will use a capacitor to set the
on/off timing, but a capacitor alone won't make anything blink.
--
Peter Bennett, VE7CEI
peterbb4 (at) interchange.ubc.ca
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca |
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