Car USB charger problems

[stupidcar]

Hi guys, I have a few questions that I can't find.

First of all, why when we use those generic USB charger in cig lighter, it doesn't blow, but when I hardwired it, it blew the regulator off. Why?

Second. What happen if I somehow really did wired it neg to pos, pos to neg?

Third. So I blew up 3 usb car charger, yes this is dumb.
Then i bought a L7805. The led lights up but the phone isn't charging.
Checked with multimeter, it is 5V but not sure the amp.

The setup is, Car -> L7805CV -> USB charger
Is the L7805CV too low to support mc34063api?
since L7805CV is 1A.

USB charger, driven by mc34063api.

Please help, thanks guys.

 

[(*steve*)]

Well, my guess is that you blew the device apart my connecting it backwards (swapping + for -). There are other ways to do this, but since you raised it as a possibility...

A 7805 will produce 5V but it will get pretty hot at the sort of currents required by phones.

It is likely that your phone senses things on the data connections on the USB to determine the capacity of the charger. Without this, it may not charge at all.

operating the mc34063 from 5V is the worst of both worlds. You need to have > 5V input voltage. Why not use the 12V it's designed for (but connect it properly)?

 

[stupidcar]

Well, my guess is that you blew the device apart my connecting it backwards (swapping + for -). There are other ways to do this, but since you raised it as a possibility...

A 7805 will produce 5V but it will get pretty hot at the sort of currents required by phones.

It is likely that your phone senses things on the data connections on the USB to determine the capacity of the charger. Without this, it may not charge at all.

operating the mc34063 from 5V is the worst of both worlds. You need to have > 5V input voltage. Why not use the 12V it's designed for (but connect it properly)?

So what u meant is that the cig lighter is definitely giving 12V right? Directly to any devices.

 

[(*steve*)]

So what u meant is that the cig lighter is definitely giving 12V right? Directly to any devices.

Well, aside from the variation in battery voltage and any spikes or noise, yes.

 

[BobK]

When the car is running it is more like 14V.

Bob

 

[stupidcar]

Well, aside from the variation in battery voltage and any spikes or noise, yes.

Well those things the switching regulator, diodes and capacitors in the USB itself will sort it out right?

Thanks btw.

 

[stupidcar]

When the car is running it is more like 14V.

Bob

Yeap same. Mine is 14.1V.
But the regulator supports way up to 40V.
It should be easy for it haha

 

[stupidcar]

Update: Okay. It works. So conclusion is.

Never ever wire a mc34063api wrongly(pos-neg; neg-pos)
No room for mistakes(Lost 3 good usb chargers).

 

[cardholderone]

IMHO, the 7805 is quite capable for a charger. I have built a few of them. Def use a heat sink, and also, some phones, including iphone, need to know if you are plugged into a higher current usb port, which some are not, so you would need a resistor for the two center conductors of the usb port which makes those data pins high, which in turn tells the phone you are connected to a port which supports higher-current charging. If you are using the charger in a vehicle, then you also need the input and output caps to filter out ripple from the alternator, which should put out around 13.8vdc, but usually don't have enough filtering to kill all the ripple.