Chosen Solution
As the title says, I have two 4.5 volt LED light strips (each one originally ran off 3x1.5 AA batteries). Can I use one 9 volt AC-to-DC power supply (wall wart type) to power these? If so, do I wire these lights in series, or parallel? Thanks!
Keep your 9V AC adapter. Connect your LED strips in series. Use a resistor from your adapter to the LED strips. You do need to know what LED’s you have and how many. Typical values for LEDs are: Red LED: 2V 15mA Green LED: 2.1V 20mA Blue LED: 3.2V 25mA While LED: 3.2V 25mA To figure out the size of the resistor use R = (V1 - V2) / I R=(9-4.5)/I (9-4.5)/0.02 4.5/0.02=225 ohms (easiest available resistor would b a 230ohm resistor) Or you can use this calculatorto figure out how to wire it by using resistors.
Connection will be in series
