# Basic Current Question

#### Ryankevin1201

Joined Sep 1, 2020
4
Hello, if I hook a circuit board up to a power supply, do you set a specific current level?

Or does the board just draw what current it needs? Could you accidentally send too much current to a circuit card?

I want to power a circuit card and it’s 5V supply, but do you usually set the current on a lab power supply or how does that work?

thank you in advance!

kevin

#### dl324

Joined Mar 30, 2015
16,116
Welcome to AAC!
Or does the board just draw what current it needs?
Yes.

#### Ryankevin1201

Joined Sep 1, 2020
4
Welcome to AAC!

Yes.
Should I be worried about limiting current or anything?

#### dl324

Joined Mar 30, 2015
16,116
Should I be worried about limiting current or anything?
You could if you're paranoid, but it isn't necessary.

If you do set current limiting, you need to make sure it's high enough for the maximum current the board will need.

#### crutschow

Joined Mar 14, 2008
33,338
The only reason to set a current limit is to protect the circuit from a short (accidental or otherwise).

#### Ryankevin1201

Joined Sep 1, 2020
4
The only reason to set a current limit is to protect the circuit from a short (accidental or otherwise).
Any ideas how I would know what to limit the current to?? Don’t want to break a very expensive CCA but need to apply power and test certain points

#### MrChips

Joined Oct 2, 2009
29,819
What is a CCA?
I am going to assume that you are using a lab bench power supply that allows you to set the voltage and current limits.
Make an estimate of the maximum current your load will require.
Set the PSU current limit to 20-50% above the maximum current.
For example, if the max load current is 100mA, set the limit to 150mA.

#### Ryankevin1201

Joined Sep 1, 2020
4
What is a CCA?
I am going to assume that you are using a lab bench power supply that allows you to set the voltage and current limits.
Make an estimate of the maximum current your load will require.
Set the PSU current limit to 20-50% about the maximum current.
For example, if the max load current is 100mA, set the limit to 150mA.
Ok - circuit card assembly