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If u don't need a stabilized voltage for the amp, or the 12V imput is stabilized use 4X1N400x in series for droping the voltage to ~9.2V .vinvin said:Hi pple,
My main supply is 12V and i have a amplifer that has 9V input.
how do i step down the voltage to 9V?
I heard before a voltage spliter is there such a thing?
Sorry i am quite new at this..
Thanks in advance..
If the 12V supply is regulated why bother with 7809? Just use something like 4X1N400x diodes in series. The voltage drop acros is somewhat the same in the 50-400mA range and the circuit will generate litle heat (so no small heatsink required).vinvin said:Thx for the reply pple,
stevez,
The input supply is for a regulated power supply. ~12V. as i measured.
Actually i need to integrate some speakers in my circuit but i only wanna use
one adaptor or power supply.. the speakers i used is some cheap PC speakers that requires 9V - 400mA. My main supply unit is 12V - 4A.
So i guess i just need to match it right?
so can use a 7809 or the circuits that "hotwaterwizard" has suggested?
Thx in advance.
Use simple arithmatic:
The resistance of the fan is about 5V/0.38A= 13.2 ohms.
The current with an 8V supply is 8V/13.2 ohms= 0.61A. The resistor value is (19V - 8V)/0.61A= 18 ohms. It dissipates (11V squared)/18 ohms= 6.7W so use a huge 10W resistor.
Use simple arithmatic:
The resistance of the fan is about 5V/0.38A= 13.2 ohms.
The current with an 8V supply is 8V/13.2 ohms= 0.61A. The resistor value is (19V - 8V)/0.61A= 18 ohms. It dissipates (11V squared)/18 ohms= 6.7W so use a huge 10W resistor.