transformers

[danielsmusic]

if i find a radio or somthing like that and the electronics inside needs 12v.
it uses a transformer to step down the voltage.
if a rip that transformer out and put a 12 volt battery on the output of the transformer will i get 240v from the input.

 

[Jay.slovak]

Theoreticaly if you connect transformer backwards (secondary to 12V) it will give you 230V (if the transformer is a 230/12V), BUT as you know transformers ONLY work with AC current, so 12V battery can't be directly used. You have to find and use suitable oscilator to make 50HZ AC from it.

 

[danielsmusic]

thanks, i didnt think it matters. i could use 2 power transistors and a 555 timer to convert dc to ac. the timer will output a + then -. using a capacitor i could create a sawtooth output and use transistors to amplifi
the voltage to 12. i hope im right.

 

[Jay.slovak]

thanks, i didnt think it matters. i could use 2 power transistors and a 555 timer to convert dc to ac. the timer will output a + then -. using a capacitor i could create a sawtooth output and use transistors to amplifi
the voltage to 12. i hope im right.

OK, that would work (teoretically, I am not an expert in these things).

 

[audioguru]

You are thinking about a DC to AC inverter circuit.
If you use a sawtooth waveform then the transistors conduct all the time with voltage across them and will get very hot.
Just use the square-wave output from the 555 to feed the base voltage divider resistors of one power transistor. The square-wave output from the 555 can also feed the base voltage divider resistors of a small transistor which can invert the 555's output and drive the base current-limiting resistor of the other power transistor.

The collectors of the power transistors connect to the outer ends of a center-tapped 24V winding and the center tap connects to +12V.

The battery, transformer and power transistors must be able to provide the power required. :lol:

 

[danielsmusic]

thanks! i never thought of that