View Full Version : Battery drains within a day for OPAMP LM324

02-26-2010, 03:37 PM
I have a very simple application. I use LM324 to amplify an input from a weightstone bridge. 2 OPAMPS are used as voltage followers, one amplifies the input and one drives a LED. I am using a 9V battery a voltage regulator 7805 and a voltage divider network of 5K (total value). When I assembled this ckt and started using it I observed that my 9V battery drained in just 1 day its voltage dropped below 5V .
Why is the ckt draining so much current, How do I prevent it?
Thanks in advance.

02-26-2010, 04:51 PM
is your circuit working properly as it should ? if yes why do you think something is wrong with your circuit...
and are you using the cheap high watt 9v battery that is commonly available ? if so then its clear that the battery is the cause of your problem.these batteries dont last very long so try using a rechargeable battery instead.

02-27-2010, 01:10 AM
is there any problem in using transformer based power supply ?

02-27-2010, 01:48 AM
is there any problem in using transformer based power supply ?

Where did the transformer come from ?? Read what OP wrote ...

Anyhow whats the current consumption when the circuit is in use ? a nine volt batter is about 300- 500 mA. also did you know LED's can drain a lot of current ...

Anyhow measure who is eating the current .

02-27-2010, 07:09 AM
1. I agree with Claus. The cheap Hi-watt batteries don't even deserve a dustbin.

2. What is resistor values of of your bridge arms. Usually sensors are low value resistors, and thus will consume current.

Anyway, you need to make use of the current measure feature in your DMM, finally.

02-27-2010, 10:23 AM
Half of your power will be wasted by the 7805 in converting your 9V input to 5V.
Use a pack of four Ni-MH batteries they will give you around 5.2 V when fully charged and 4.8V when drained. They will also be able to provide power for a longer time.

03-07-2010, 07:01 AM
I am trying to create a consumer product that needs larger battery life. Vivek what do u mean by using current measure feature

03-07-2010, 12:38 PM
He means the current consumption using your multimeter for your product and calculate maH , which will tell how long the thing will last on the battery.

03-08-2010, 06:13 PM
Checks whats the current consumption of your device.Then we can think that whats the problem & what should be the ideal current consumption.We can also calculate the running time of your device.

For eg:

Your device uses 500 Milli Ampere & battery supplies 4500 milli ampere hours( mah) so your device will run for 9 hours.

03-08-2010, 06:15 PM
Whats your device about??
If the device is not mobile you can even use transformer based power supply.

03-08-2010, 11:00 PM
Can't you run the LM324 directly from the battery? They can handle 9V easily.

Use high value resistances where possible. The circuit will draw lesser current this way. F.e., the resistor divider could be made from 39k & 10k instead of 3.9k &1k.

03-10-2010, 02:21 PM
The total current consumption of my device is 8 mA. 8 mA is what the multimeter showed when I connected it in series between the +terminal of the battery and the ckt. The short circuit current of battery is 700 mA. How do I determine for how long the battery would last. I am using the Hi-watt blue color battery. It doesn't mention any amphere-hour rating.