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jenny
New Member
2 Posts |
 Posted - Mar 10 2010 : 06:28:22 AM
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what are the uses of the 10000uF cap. before the regulator IC and a.1uF and .01uF cap. after the regulator IC in the power supply .... hope you will help us |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Mar 10 2010 : 06:48:00 AM
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Ripple rejection usually for electrolytics and noise filtering usually for the smaller capacitance ceramic types or polyester.
Design your circuit with a higher capacitance on Vin than Vout. This will prevent Vin being less than Vout when they discharge at power off. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Mar 10 2010 : 1:23:13 PM
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Exactly. The bridge rectifier puts out a pulsing DC, which gets filtered by the big capacitor. I chose it following a rule I heard years ago "2000uF per amp". Going a little smaller or a little bigger won't hurt.
The small ceramics are for noise filtering. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Mar 11 2010 : 12:46:24 AM
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Thinking like an engineer to decide on what value of ripple rejection capacitor you'll need requires you to know what frequency the supply voltage is typically 50Hz to 120Hz(Thinking full wave rectification). Y'all also need to know what the maximum current draw is for your load as the higher it is the more ripple you get i.e. you'll need a larger value capacitor to hold the charge above the minimum threshold voltage that will linked to your voltage regulator. It doesn't have to be a voltage regulator after the RR capacitor but there is always a minimum voltage that must be satisfied when under load of which is decided by the engineer who would know the tolerances of the components he/she is using.
Correct me if I'm wrong but in an ideal circuit there would be no need for those tiny ceramic capacitors to filter the noise. The reason why you need them in reality is because those fat electrolytic have lead inductance which prevents them from filtering off high frequency noise. The smaller and more compact ceramic types have less length of metal for those little electrons to travel through so there inductance is very low and so they are more pure... capacitively, if that's even a word. Or/and it could be the same story but think resistance instead of inductance.
I've never heard an explanation for why we have those small capacitors but I would think it has something to do with what I just said. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Mar 11 2010 : 01:22:09 AM
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If you really wanna be smart know this.
Capacitors in reality have Capacitance, Inductance and Resistance.
Inductors in reality have Capacitance, Inductance and Resistance.
Resistors in reality have Capacitance, Inductance and Resistance.
So what's the point of calling these things Capacitors, Inductors and Resistors?
Well,
(1) We assign the name of "Capacitor" to some electrical device that is primarily capacitive in functionality.
(2) We assign the name of "Inductor" to some electrical device that is primarily inductive in functionality.
(3) We assign the name of "Resistor" to some electrical device that is primarily resistive in functionality.
Ahh, the ideal world would be much more simpler.
Did you know that in reality there is actually a schematic diagram for passive components such as Inductors, Capacitors and Resistors? You should have been able to figure that out already based on what I have said above. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on Mar 11 2010 04:08:10 AM |
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pebe
Nobel Prize Winner
United Kingdom
1078 Posts |
Posted - Mar 11 2010 : 04:19:59 AM
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quote:
Originally posted by wasssup1990
....Correct me if I'm wrong but in an ideal circuit there would be no need for those tiny ceramic capacitors to filter the noise. The reason why you need them in reality is because those fat electrolytic have lead inductance which prevents them from filtering off high frequency noise. The smaller and more compact ceramic types have less length of metal for those little electrons to travel through so there inductance is very low and so they are more pure... capacitively, if that's even a word. Or/and it could be the same story but think resistance instead of inductance....
An electrolytic capacitor also has a series resistance. The anode is an aluminium foil, the dielectric is its anodic film, and the electrolyte is the cathode. There is also a further alunimium conductor (frequently, but wrongly, called the cathode) that serves as a collector to transport electrons to and from the electrolyte.
That electrolyte has a finite resistance called the 'Equivalent Series Resistance'. I have no idea why it's called 'equivalent' because it is pure resistance in series with the capacity and the lead inductance. |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Mar 11 2010 : 05:04:53 AM
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Very interesting.
I hope someone else is being enlightened from this information too.
Same deal with active devices such as BJTs. In BJTs the capacitance's (mostly internal) are very important to consider. Maybe not so much if switching at low frequencies. Critical when dealing with RFs.
I can only imagine what computer motherboard engineers go through to get their boards working. You sometimes see those squiggly copper tracks on the motherboard. They are primarily used to compensate for length so that all signals on the data bus(es) arrive at the same time to the next IC chip. So in this case you must consider the speed of light because you're operating at such high data rates and frequencies.
Who knows? We may come to realize one day that biological computers are far more efficient than silicon. I need to point no further than that hidden thing between our ears called a "Brain". It's a naturally evolved electrochemical computer pretty much. One day it will be emulated in silicon, we may then discover that we should have just used the technology that we already had inside us for computing and solving problems in real time. Silicon can be knocked out by an EMP natural or otherwise... brains can't.
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When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
Edited by - wasssup1990 on Mar 11 2010 05:05:33 AM |
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jenny
New Member
2 Posts |
Posted - Mar 11 2010 : 06:39:13 AM
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| thankyou so much for all those who answered our query |
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wasssup1990
Nobel Prize Winner
A Land Down Under
2261 Posts |
Posted - Mar 11 2010 : 06:43:36 AM
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| You're welcome. Make good of the info here. |
When one person suffers from a delusion it is called insanity.
When many people suffer from a delusion it is called religion. |
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Mar 12 2010 : 10:35:24 AM
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| Basically. |
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power supply
