Go Down

Topic: Testing a Voltage Regulator (Read 1 time) previous topic - next topic

marian42

Hi,

I want to test a volatage regulator.

I applied a voltage betweet Vin and GND and measured between Vout and GND. I measured no voltage and the regulator got hot.
What did I do wrong?

How can I regulate 7.2V to 5V?

bobthebanana

You bought a negative voltage regulator. Look for a 7805 instead of the 7905

lax123

Quote
How can I regulate 7.2V to 5V?

why would you do that with a Negative voltage regulator when it says in the datasheet: DC input voltage: - 5 to - 18 V, and it already told you its a negative one in the second line of the datasheet?

7805 should work, it has a voltage dropout of 2V, so if u get below 7V at the input it wont be able to regulate to 5V.

marian42

#3
Feb 06, 2013, 07:51 pm Last Edit: Feb 06, 2013, 07:57 pm by marian42 Reason: 1
7805 should work, it has a voltage dropout of 2V, so if u get below 7V at the input it wont be able to regulate to 5V.

Are there regulators with a smaller dropout?
The 7.2V comes out of a battery pack. It will probably drop when it is almost discharged. Can I use the 7805 anyway?

If the regulator is correct, can I just connect the Vin and Vout to it or do I need a further circuit like this:

KeithRB

The capacitors are there to prvent oscillations and smooth out fluctuations, use them. If you want to input less than 7 V, look up low dropout "LDO" regulators.

Go Up