My Daughter and I are building a "Battery Buggy" for Science Olympiad. We have the power source (12v battery pack), switches, and motor all wired up and working. Now we want to add a laser pointer to help with alignment. The rules state the laser pointer must be powered from the same 12v battery pack as the motor. Rules also limit electronic components to batteries, switches, relays, potentiometers, resistors, and motors. The laser pointer requires 4.5vdc and pulls 50mA. I need to get the 12vdc battery pack to 4.5vdc. I figured the only way to do it with the component limitation is to build a voltage divider with two resistors. Problem is, I don't remember how to determine the resistor values. Can anyone help with this? I am attaching the circuit diagram.
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