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..

 

Hello,

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.

Bertus

 

I know that problem. It has been asked before.

Guess what is the reason.

 

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.

 

thanks a lot.. i ve changed the battery and its working..

 

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.

 

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.