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mobile charger circuit help

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The datasheet for a BCP68 shows that its beta (hFE DC current gain) has a very wide range of from 85 to 375 as shown on the datasheet. They test them all and select ones with a beta of 160 to 375 averaging 250 (marked 25) with a much narrower range as shown in the datasheet.
Am I wasting my time here because you haven't even looked at the datasheet????
 

yasir_ali86 said:
Hello all. which transistor is this T1? i did not find its datasheet on google.
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To me it looks like bc546b will do

---------- Post added at 08:30 ---------- Previous post was at 08:20 ----------

I made a mistake try BC 846B

---------- Post added at 08:31 ---------- Previous post was at 08:30 ----------

I made a error try transister BC846B
 

today i tried up with 7805 regulator. But after all this the circuit is not charging my nokia 1100. i checked the voltage when charging, it was exact 5v and then i checked the current unfortunatley i know why the current is not going above 1.7mA. what could be the problem? i am powering this circuit from my lab supply i designed. the input to the circuit is from 7812 Ic.
 

If the battery is a lithium type then maybe it cannot be charged anymore.
Maybe the charging circuit in the phone is defective.
 

the charging circuit in the mobile phone is working fine Because the original charge of the mobile is chaging it in the normal way. may be problem is the input from 7812. if i put 4 AA battery instead of 7812 output. will it work?
 

yasir_ali86 said:
the charging circuit in the mobile phone is working fine Because the original charge of the mobile is chaging it in the normal way. may be problem is the input from 7812. if i put 4 AA battery instead of 7812 output. will it work?
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If the input to the 7805 is 7 or more then its output will be regulated at 4.75V to 5.25V. Maybe you should replace the 7805 with an LM317 adjustable regulator (plus its two resistors) and adjust its output to be exactly 5.0V. An LM317 also needs its input to be at least 2V higher than its regulated output.
What is the output voltage of the 7812?

Four AA alkaline cells are 6.4V when brand new and they drop to less than 4.0V as they are used so they make a poor power supply for a charging circuit. They will not power an ordinary 5V regulator.
 

the output of 7812 ic is 11.90v. you think that i ishould you lm317 instead of 7805? and i should not use AA batteries to power the circuit. is this what you are sujjesting me?

---------- Post added at 16:42 ---------- Previous post was at 16:40 ----------

and as i said that i checked the charging voltage. the voltage is 5v exacxtly But the current is 17mA. and NOT going up.
 
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Does your 7805 have the input and output capacitors shown on its datasheet to prevent it from oscillating?
 

actually i yesterday i did not had them but today i did add both the capacitors But still the charginig current is 17mA and NOT going up or down. i thought it mayh be the problem of bad 7805 regulator and i changed the regulator But the problem is still there.
 

If your old Nokia 1100 cell phone cannot charge its old battery when you feed it 5.0VDC with plenty of current available then either the charging circuit in the phone or the battery is defective.

Look in Google. There are hundreds of threads about this problem with that old cell phone.
 

But the problem as i told you is in the charging circuit. my circuit of 7805 regulator is not supplying current more than 17mA. that's why i am asking here that what could be the problem?
 

View the output of your 7805 regulator on an oscilloscope while it is powering the charging circuit in your cell phone to see if it is oscillating.
 

ckshivaram said:
they will charge...... but will spoil your batteries soon.... i am a victim of that.. later had to design my own good charger with modifications in the circuit...
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can u post the design of your charger??/along wid circuit diagram n specs?

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can u post the design of your charger??/along wid circuit diagram n specs?
 

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