# Power Supply

Discussion in 'The Projects Forum' started by tahir51214, Apr 30, 2013.

1. ### tahir51214 Thread Starter New Member

Nov 11, 2011
29
1
Im a beginner. In a project im assigned to use 9V battery, I have a variable power supply. Can I use it with 9V selection instead of battery? Pls help me out

2. ### crutschow Expert

Mar 14, 2008
13,509
3,385
Yes. In general you can use a regulated DC power supply of comparable current capacity to replace a battery.

3. ### tahir51214 Thread Starter New Member

Nov 11, 2011
29
1
Thanks, so small difference in current will not matter??

4. ### ScottWang Moderator

Aug 23, 2012
4,933
777
Because we don't know the details of your project, and the 9V battery just can offer a small current, so when you using the variable power supply to replacing the battery, the circuit could be working fine, but it doesn't means that it will also working ok with 9V battery.

Using the variable power supply to do the experiment is very common, I also do that, but if the circuit will working with a 9V battery then I will calculate how much current that I should provide for it, I will also measure the current.

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5. ### crutschow Expert

Mar 14, 2008
13,509
3,385
A circuit normally takes only the current it needs at a given voltage. So you just need a power supply that will supply more current then that. Any power supply excess current capability is just ignored by the circuit.

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6. ### wayneh Expert

Sep 9, 2010
12,396
3,246
The only concern - and it's a bit of a reach - is that you're working with a poorly designed circuit that relies on the low current capacity of the 9V battery. This hypothetical circuit might be operating at 6V once it pulls down the battery voltage when under load. When you come along with a genuine "unlimited" 9V supply, the circuit may not last as long.

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7. ### KMoffett AAC Fanatic!

Dec 19, 2007
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