want help with 7805 voltage regulator

Discussion in 'The Projects Forum' started by Amanpreet Singh, Jan 2, 2013.

  1. Amanpreet Singh

    Thread Starter New Member

    Jan 2, 2013
    Actually i am making a line following robot. I have made connections of atmega16 with the corresponding pins on l293d and 7805. When i connect it to the 9 v dc battery, the input itself reduces to around 4 volts.. And the output too, drops to arnd 2.7 v.. Each component i am using has been tested before by making a circuit on breadboard. Here is the circuit if you want.
    Please help me as soon as possible. I ve tried very hard to figure out the error but I am unable to do so.. I will be highly thankful to you..
  2. bertus


    Apr 5, 2008

    How much current do the motors take?
    If you are using a small 9 Volts battery, its internal resistance will reduce the voltage at the output.
    The battery will be exhausted very soon.

  3. takao21203

    Distinguished Member

    Apr 28, 2012
    I know that problem. It has been asked before.

    Guess what is the reason.
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
    The minimum input for an LM7805 is 7 V; your battery is not providing that much voltage because is it partially depleted and/or overloaded.
  5. Amanpreet Singh

    Thread Starter New Member

    Jan 2, 2013
    thanks a lot.. i ve changed the battery and its working..
  6. SgtWookie


    Jul 17, 2007
    You will spend a lot of money on those 9v batteries and have to change them very often. They work OK for SMALL load currents, but are a poor choice for more current-hungry applications. If your project includes a relay, a motor, solenoid, etc. you should avoid them.
  7. takao21203

    Distinguished Member

    Apr 28, 2012
    Lithium batteries are good for robots, or high quality NiMH.

    I recommend Energizer, and Duracell. Both of these outperform no-name cells, and they work for a long time with electronic chargers.

    No-name cells often become defective very quickly, and after a while, are only good for lower currents.

    I have at least 100 AA and AAA cells here so this statement is based on experiencee.

    You can however still recharge bad cells using a low-tech charger. They will get some charge, good enough for low currents.
    Amanpreet Singh likes this.