1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

Voltage regulator circuit

Discussion in 'Automotive Electronics' started by BioniC187, Nov 27, 2012.

  1. BioniC187

    BioniC187 Member

    Joined:
    Aug 9, 2011
    Messages:
    281
    Likes:
    10
    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?
     
  2. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

    Joined:
    Mar 28, 2011
    Messages:
    9,161
    Likes:
    909
    Location:
    Rochdale UK
    ONLINE
    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....
     
  3. BioniC187

    BioniC187 Member

    Joined:
    Aug 9, 2011
    Messages:
    281
    Likes:
    10
    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
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

    Joined:
    Mar 28, 2011
    Messages:
    9,161
    Likes:
    909
    Location:
    Rochdale UK
    ONLINE

    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.
     
  6. BioniC187

    BioniC187 Member

    Joined:
    Aug 9, 2011
    Messages:
    281
    Likes:
    10
    Alright, can you post a diagram of your circuit wit hthe lm2576?
     
  7. 4pyros

    4pyros Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2010
    Messages:
    4,368
    Likes:
    282
    Location:
    Pennsylvania, USA
    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.
     
  8. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

    Joined:
    Mar 28, 2011
    Messages:
    9,161
    Likes:
    909
    Location:
    Rochdale UK
    ONLINE
    The circuit diagram for the LM2576T is in the datasheet... Copy it item for item...
     
  9. BioniC187

    BioniC187 Member

    Joined:
    Aug 9, 2011
    Messages:
    281
    Likes:
    10

    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
     
  10. 4pyros

    4pyros Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2010
    Messages:
    4,368
    Likes:
    282
    Location:
    Pennsylvania, USA
    It only comes in 5,8,10,12 or 15 volt outputs. No 7 volt vershoins.
     
  11. BioniC187

    BioniC187 Member

    Joined:
    Aug 9, 2011
    Messages:
    281
    Likes:
    10
    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
     
  12. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

    Joined:
    Mar 28, 2011
    Messages:
    9,161
    Likes:
    909
    Location:
    Rochdale UK
    ONLINE
    I told you that in post #4... LDO types will protect your circuitry..
     
  13. 4pyros

    4pyros Well-Known Member Most Helpful Member

    Joined:
    Oct 22, 2010
    Messages:
    4,368
    Likes:
    282
    Location:
    Pennsylvania, USA
    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.
     

Share This Page