need help with my USB phone charger

[franzey]

I would like to request some assistance with our charger..It doesn't seem to work properly when i use it to charge a Samsung E1125 phone but the transistor TIP127 and the regulator LM7805 gets very hot. It's my first time here and I've searched a few topics but I can't find what I'm looking for.

 

[4pyros]

What are V1-V4?

 

[franzey]

Well sir we used two stepper motors as generator..Each stepper has two coils inside..Those are the V1-V4

 

[4pyros]

Can you measure the output current of the 7805?

 

[JimB]

What voltage are you expecting from your stepper motors?
Who or what is going to turn them for several hours to charge the battery?

Your MC34063 circuit produces 12 volts, if you are using that to charge the 12v battery it will not work.
You will need more than 12v, how much more depends on the battery chemistry. (And dont forget about the voltage drop across diode D1).
Why are you using a 12 volt battery when you only need 5 volts?

What is the purpose of the BC548 and LED1 ?
If it is supposed to be a charge state indicatot for the 12v battery, it will not work well.

What is the TIP127 circuit supposed to be doing? (Apart from wasting energy as heat).

Do you really need those resistors on the D+ and D- pins of the USB connector?

So, you have some stepper motors whirring away and a voltage converter circuit to charge a 12v battery.
You then have a regulator (7805) and some other odd circuit (TP127) which are dissipating more than 2.4 times (12/5) the energy that you put into the phone battery.

No wonder the TIP and the 7805 are getting hot.
Are the TIP and 7805 mounted on heat sinks?

You may want to re-think this circuit.

JimB

 

[franzey]

What voltage are you expecting from your stepper motors?
- we could generate 15V from the motors.

What is going to turn them for several hours to charge the battery?
- bicycle

Why are you using a 12 volt battery when you only need 5 volts?
- we plan to use the battery to other circuitry like the bike lighting, but we're focusing on the charger first.

What is the purpose of the BC548 and LED1 ?
- indicator that the battery is at 12v or full charge.

What is the TIP127 circuit supposed to be doing?
- transistor as a switch, on when battery is more than 10v, off when battery is less than or equal to 10v.

Do you really need those resistors on the D+ and D- pins of the USB connector?
- yes(i'm not sure of those values though)

Are the TIP and 7805 mounted on heat sinks?
- yes


any suggestion what we should do?.

should i remove that tip127?




it's working now if i remove the resistors..but i won't be able to charge other devices..any suggestions?









it's working now..

 

[4pyros]

it's working now if i remove the resistors..but i won't be able to charge other devices..any suggestions?

The resisters set up a voltage divider for iphones.
At 125K ohms total thay should not have any effect on the power supply.
Can you measure the output current of the 7805?
It should not be any higher than 500ma for USB.

 

[Nigel Goodwin]

The resisters set up a voltage divider for iphones.
At 125K ohms total thay should not have any effect on the power supply.
Can you measure the output current of the 7805?
It should not be any higher than 500ma for USB.

It's not feeding 'USB', it's just a charger using a USB socket - the charging current is also set by those resistors for iPhones, and could well exceed 500mA from a charger.

I notice he said he has heatsinks, but makes no mention of how large they might be?.


There's also the essential capacitors missing on the 7805 (so it could be oscillating), and what is the TIP supposed to be doing?.

 

[audioguru]

what is the TIP supposed to be doing?.

"- transistor as a switch, on when battery is more than 10v, off when battery is less than or equal to 10v."

 

[Nigel Goodwin]

"- transistor as a switch, on when battery is more than 10v, off when battery is less than or equal to 10v."

And why would that help anything? - who cares if the 7805 is regulating or not, as long as it's feeding 'something' to the battery

 

[4pyros]

the charging current is also set by those resistors for iPhones

The voltages on the data pins are needed for iphones, thay will not charge without them.
Apple put them there so you have to use there chargers.

and could well exceed 500mA from a charger.

Yes maybe but the USB plug its self is rated at 1.5 amps.

 

[4pyros]

And why would that help anything? - who cares if the 7805 is regulating or not, as long as it's feeding 'something' to the battery

Its to protect the storage battery.

 

[blueroomelectronics]

I would use a more efficient switch mode regulator. When charging devices with human power I would think you'd want to waste as little energy as possible.

Your linear 7805 will get very hot with 12V pouring into it while charging a typical phone.