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Voltage regulator circuit

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BioniC187

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Hey all,
I want to connect my arduino in my car. So i was looking at the lm2904 as it is designed to vehicle application.
Problem that i am having is that in the datasheet, it has a 5v output and an 8v output. So how do i go about selecting either? or is the lm2904 only for 5v or 8v and not both? anyone has any experience with these regulators?
 

Ian Rogers

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The Arduino already has a decent 5v regulator already... Dropping from 12 - 13.6V from the cars charging system can sometime heat this reg up... I use a LM2940T-8 this gives anothe step down from the battery voltage.... Tiny PCB ( stripboard ) with a cap either side....
 

BioniC187

Member
I know it does have a voltage regulator, but i don't want to stress it. Rather build another circuit, so if anything bad happens, that circuit will pop before the arduino. The voltage from a car is not very clean, and i would prefer to filter it and drop it, before getting to the arduino
 

Ian Rogers

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I fit my equipment onto cranes.... New and old... sometime the voltage is as bad as it can get... I use a tiny LM2576 SMPS it survives anything ( well almost ) This is very stable and never gets hot.... Most companies, doing what we do, use the LM2940 series... LDO type.. They fair very well.
 

4pyros

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Problem that i am having is that in the datasheet, it has a 5v output and an 8v output
It is a fixed voltage regulater. It only has one output. The voltage is the last part of the part number.
You should use a part number LM2940T-8 for 8 volts.
 

BioniC187

Member
It is a fixed voltage regulater. It only has one output. The voltage is the last part of the part number.
You should use a part number LM2940T-8 for 8 volts.


Thanks pyros :) needed to know that. Now an arduino will be running fine with 8V so im gonna choose at 8V if possible, or 7V
 

BioniC187

Member
Alright cool. I have one of those 7808 voltage regulators here, but i read in a few places that the lm2940 is better coz it is made for vehicle application
 

Ian Rogers

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Alright cool. I have one of those 7808 voltage regulators here, but i read in a few places that the lm2940 is better coz it is made for vehicle application

I told you that in post #4... LDO types will protect your circuitry..
 

4pyros

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Alright cool. I have one of those 7808 voltage regulators here, but i read in a few places that the lm2940 is better coz it is made for vehicle application
Yes the LM2940-XX will have more built in protection than a LM7808. But the 7808 will still work. You can add external protection to the 7808.
 
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