I have a motion clock that runs off of two C cell batteries. One battery runs the movement at 1.5 volts. That other battery then continues in series to run the motion part delivering 3 volts to it. I would like to use a 3 volt dc plug in power supply to run the entire clock, but do not know how to separate 1.5 volts from it. I would not be opposed to using a 4.5 volt power supply if that is what I would need to do - 3V + 1.5V. The movement is quartz, so I'm sure the amperage draw is small. The motion part is an electromagnet that pulses and pushes a permanent magnet away from it to move the pendulum. If possible I would like to put this on a board that would press fit into where one of the batteries go, so it could be returned to battery operation in the future if desired. I'm also planning to use a jack plug that accepts the power supply/dc transformer, so it could be easily replaced in the future if it burns out. Thanx in advance for any help.
I have run battery powered quartz electric clocks on mains derived low voltage DC for about 2 decades .They work fine .I made my own low idle current linear regs from garden variety BJTs like BC337 ,BC327 .The battery clock does not need a highly accurate DC voltage because it is designed to keep time as the 1.5 volt cell ages .Now days you could use a LDO P channel reg .I did not use LM317 because the idle current wastes much more power than the clock .I used a combination of supercaps and electrolytic caps to allow operation during short power outages which are common in my area .Some years later I hooked up a smoke alarm to the system .
There are very cheap and easy to use voltage regulator modules available on Ebay for like $ 1 each, I suggest you get two of those.
Then connect them like this:
You should use a DC adapter of at least 5 V so you could use a USB phone charger. I would not go higher than a 12 V input voltage.
Before you connect the clock, use the small screw on the blue variable resistor to set the output voltage to 1.5 V and 3 V.
Indeed as Neil suggests in his comment, you could also use a resistive divider or (what I'd do) a couple of diodes in forward mode (and a resistor to 3 V) to make 1.5 V from 3 V. You'd still need a 3 V adapter though and these might be hard to find.
Also the cost of the individual components to make that will not be less than just buying two modules. We EEs often have these components in our part drawer so for us they're "free" but since my guess is that you would have to buy everything, it might be easier to just get two cheap LM317 based regulator modules.