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Power Supply Selection Guidelines Keep the following requirements in mind when selecting your power supply. - Power source, input voltage and Frequency (AC/DC) - Number of DC devices to be powered - Voltage requirements of DC devices - Wattage/Amperage of each DC device required - Maximum/Peak draw of each DC device - Physical space available and mounting requirements - Check for applicable safety approvals for the location and application The conversion of Volts to Watts is governed by the equation Watts = Amps x Volts. Note: there are 1000 milliamps (mA) in 1 amp. While most power supplies allow operation at 100% of rated capacity, it is recommended that an extra 30% be factored in. This allows the power supply to run cooler, more efficient and extends the life. For example: Device #1 requires 24 Vdc and draws 1 Amp [24Vdc X 1A = 24 Watts] Device #2 requires 24 Vdc and draws 500mA [24Vdc x (500/1000)A = 12 Watts] Total wattage required is (24 + 12 watts) x 1.3 = 46.8 Watts Round up to the nearest 10 watts would be 50 watts. Therefore, you would select a power supply rated at 50 watts and outputs 24 volts DC.