Battery Charging Circuit

[pllp89]

Hi all,

I really desprately need help on this. It's a school project and i need to explain this circuit by tomorrow. have been researching and everything but i wasnt able to understand it at all.
could any of you kindly explain it to me ? on how each and every components works, affects. especially for the comparator( it's an op amp) part. With and without feedback,what it actually affects ? and can i actually know how to calculate the gain for op amp ?
i've got to go study on capsense proximity sensor for now,which is dued tomorrow too. so i really hope you guys would really help me out. PLEASE PLEASE PLEASE.

i've attached the schematic and the component list. please take a look.
i thank each and everyone of you.
THANK YOU!!

https://i229.photobucket.com/albums/ee197/pllp89/componentlist.jpg
https://i229.photobucket.com/albums/ee197/pllp89/Schematic-2.jpg

 

[MrAl]

Page not found?

 

[pllp89]

should be okays already.. take a look ?

 

[pllp89]

need help need help ...

 

[marcbarker]

5 V supply is potted down to make Vref.

When plugged into USB, it chrages the battery until it gets warm.

The thermistor turns off the transistor.

Also switches off the LED.

 

[pllp89]

the z1a and the transistor part.. how it works ?

 

[marcbarker]

works very well, thank you.

As battery warms up, Vtmp falls.

Z1a compares Vtmp with Vref.

When Vtmp < Vref, Z1a turns off transistor.

Transistor turns off because of holes are no longer injected into the silicon by the current flowing into the base-emitter junction, resulting in the cessation of minority hole carriers, which had previously allowed current to pass through the reverse-biased collector-base junction of the bipolar junction transistor.

 

[pllp89]

Transistor turns off because of holes are no longer injected into the silicon by the current flowing into the base-emitter junction, resulting in the cessation of minority hole carriers. QUOTE]

may i ask, to explain this ? sorry, i don't understand this part..
and can i know the equation for feedback ? and how to calculate the gain for the amplifier based on this circuit ? cause i tried explaining that if the output at z1a is 0v, current will flow. if its 5v, current will now flow. then my teacher said its wrong. impossible that it's 0v. and he want me to calculate..

thankyou..

 

[marcbarker]

That last paragraph was intended as a joke on you, but it seems to had backfired on me!

I suspect that the information you are asking for is something you were expecting yourself to had in learned class but didn't. Perhaps you didn't get it at the time, and instead of holding up the rest of the class while you got it, you decided to work it out at home later. Now time is running out.

If I'm correct, I sympathise with you. I also admire you sharing this with us and risking daft postings of mis-information based on misunderstood questions.

What I'll do is leave this for other experienced posters to pick up.

can i know the equation for feedback ?

and how to calculate the gain for the amplifier based on this circuit ?

**broken link removed**

 

[pllp89]

sighs, i'm sorry. cause it really is very urgent. so could make do with any explaination and all. thanks for all your advice though.

 

[audioguru]

That battery charger project is on the internet.
The text of the project explains how it works.

 

[marcbarker]

That battery charger project is on the internet.
The text of the project explains how it works.

can you remember any keywords to find the URL?

 

[audioguru]

I entered USB Battery Charger Circuit in Google and it is the second link:
Build a USB Powered AA NiMH and NiCd Battery Charger

Why couldn't you find it??

 

[pllp89]

nahs, i found it. but the explaination doesnt includes what i want.. his description is good, but not enough for explaining to my teacher.