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How to change the direct current of auto power supply


namam
04-17-2017, 03:47 AM
Good afternoon~:眨眼:
I would like to ask some advice from you.Please look at the following circuit:
https://gss0.baidu.com/-Po3dSag_xI4khGko9WTAnF6hhy/zhidao/pic/item/43a7d933c895d143ae4f0f1179f082025aaf07c2.jpg
In this circuit, How to chose the capacitor in two ports of 7805 if changing the direct current from 12V into 5V? The reason is I need to change the direct current of auto power from 12V into 5V which will be used by singleship. Do you have any specific formulas ?

Thanks all.

shorod
04-21-2017, 07:51 AM
Have you reviewed the datasheet for the LM7805? The datasheet usually does a pretty good job of providing formulas for calculating the capacitor values.

Also, do you know what current draw you'll have on the 5V? These 7805 regulators are not very efficient and will get pretty hot if you are running them near their 1-1.5 amp rating. You'll need a pretty decent heat sink. A better option might be to buy one of the very inexpensive DC to DC converters available several places online. They are very small, very efficient, and come pre-built so all you need to do is connect the 12V in and the 5V out.

-Rod

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