# How do you set a constant current in a power supply?

## How do you set a constant current in a power supply?

Most power supplies cannot be “put” into the constant current mode. The output settings of the power supply and the load resistance determine whether the power supply is in constant current. The power supply inherently stays in constant voltage mode.

## What happens if you don’t use a resistor with an LED?

When hooking up an LED, you are always supposed to use a current-limiting resistor to protect the LED from the full voltage. If you hook the LED up directly to the 5 volts without a resistor, the LED will be over-driven, it will be very bright for a while, and then it will burn out.

Do I need a resistor for a 12v LED?

1 Answer. AFAIK there is no, or at least no common, led diode that is typically 12V forward voltage by it self. 12V led are modules that consist of some combination of diodes and resistors to make them suitable for 12V power applications without needing extra current limiting.

Will a 9v battery power a 12v LED?

you can use 9v battery for 12v Led . Just only the brightness is less than 12v battery . if you need only Light purpose then you can use 9 volt instead of 12 volt supply.

### Do I need a resistor for each LED?

The simplest circuit to power an LED is a voltage source with a resistor and an LED in series. The ballast resistor is used to limit the current through the LED and to prevent that it burns. If the voltage source is equal to the voltage drop of the LED, no resistor is required.

### How many LEDs can be connected in parallel?

Wiring LEDs in parallel allows many LEDs to share just one low voltage power supply. We could take those same four 3V LEDs and wire them in parallel to a smaller power supply, say two AA batteries putting out a total of 3V and each of the LEDs would get the 3V they need.

Can I connect a LED directly to a battery?

Five-volt LEDs can be connected to a nine-volt battery, but an external resistor is also needed in order to drop the voltage to the five volts required.

Where does the resistor go on a LED?

Since this resistor is only being used to limit current through the circuit, it can actually be located on either side of the LED. Placing the resistor on the positive (anode) side of the resistor will have no differing effects from placing the resistor on the negative (cathode) side of the LED.

## What happens if I use the wrong resistor?

We need to turn the resultant current signal into a voltage signal (for A-D conversion, typically,) by inserting a burden resistor. If you fit one of the wrong ohmic value that curtent-to-voltage conversion will be away, and the current indication wildly in error.

## Which leg is longer on LED?

The longer leg is the positive side of the LED, called the “anode,” and the shorter leg is the negative side, called the “cathode.”