Measure the current of a single LED module

To calculate the number of switching power supplies required for an LED display, you first need to measure the current of a single LED module, then use the power supply parameters to calculate the number of modules a single power supply can support, and finally determine the number of power supplies based on the total number of display modules. The specific steps are as follows:

Measure the current of a single LED module
Equipment preparation: Prepare the LED display module to be tested (such as a P10-4S outdoor LED display module), a multimeter capable of measuring DC current within 10A, several wires, electrical tape, wire strippers, an LED display control card, and an LED display power supply.

Correct wiring: Connect the multimeter in series into the LED module's working circuit. The specific wiring sequence is:
- Connect AC 220V to the input of the LED power supply.
- Connect a wire from the positive output terminal to the multimeter's red probe (positive).
- Insert the red probe into the red "10A" port on the multimeter.
- Connect the black probe to the red wire (positive) of the module's power line.
- Connect the module power lines normally to the module.
- Connect the black wire (negative) of the module power line back to the negative output terminal of the LED power supply.

Measure readings: Plug in the input power socket and turn on the LED display. The current of a single module will fluctuate with the displayed content. Press the test button on the control card to switch the screen state, and record the current data for different states, for example:
- The current is highest when displaying full white, approximately 5.8A.
- The current is 3.3A for red and green states.
- The current is 2.0A for the blue state.
- When returning to normal program playback, the current fluctuates between 1–2A.

Calculate the number of modules a single switching power supply can support
Determine the effective power of the power supply: Take a common 200W switching power supply as an example. The manufacturer gives the loaded parameters as "Output 5V 40A" with an effective conversion rate of 88%. Calculate the effective power provided by the LED switching power supply using the formula:
$P = 88% × 200W = 176W$

Calculate the maximum power consumption of a single module: According to the formula $P = UI$, with a known module operating voltage $U = 5V$ and maximum current $I = 5.8A$ when displaying full white, the maximum power consumption of a single LED module is:
$P_1 = UI = 5V × 5.8A = 29W$

Calculate the number of modules supported: Divide the effective power of the power supply by the maximum power consumption of a single module to get the number of modules a single LED switching power supply can support:
$n = P/P_1 = 176W / 29W ≈ 6.069$

Since the number of modules must be an integer, the LED power supply will not be overloaded if it supports no more than 6 modules. The maximum supported number calculated based on the maximum current is considered the safe load. During normal playback, the working current is often only 1/3–1/2 of the maximum current, but to ensure safe and stable operation of the power supply, the maximum current is used for the calculation.