So this was the year we bought a AC-powered O-gauge Lionel train and a battery-operated village to add to our Christmas tree decor. The problem, the village eats batteries like a kid eats cookies.
Here is the setup:
- 3 village houses running on (3) AA batteries each [1.5V * 3 = 4.5V each house]—batteries last the longest here, two houses have 1 LEDs, the church has 2 LEDs.
- 1 village skating rink that also plays music and goes through batteries faster (3) AA batteries [4.5V]. There are 2 bright LEDs, 2 lamp LEDs, and 16-17 LEDs that blink to the music.
- 2 street lamp posts running on (1) 3.5V CR2450 button lithium battery [3.5V each lamp). The box calls it 3V—these batteries go fast too.
The bulbs are not designed to be replaced and there is no such indication of the watts or mA consumption.
The options as I see it are to buy a AC-to-DC power adapter for each of the two circuits above—3.5V circuit/adapter and 4.5V circuit/adapter. I have found for example, an AC adapter with a DC output of 3.5VDC@400mA. I have no idea if that would work for the lamp circuit and if done in parallel to keep volts the same at 3.5, does that 400mA become 800mA and what that means to the bulb that is currently running on 3.5V@650mAh. I guess what I need to learn is what rating that bulb could be on a unit where a bulb is not designed to be replaced or its mA use documented.
The other option of course is to create a custom circuit board and get my hands dirty in the details—I have 10.5 months so I'm open to it. I would imagine a single AC input split into two circuits that are individually transformed. I would love to have a setup on a board where I had screw terminals, one for each circuit to add each unit (house or lamp) to the board. Are there kits for this?
I greatly appreciate any thoughts, directions, and/or lessons.
UPDATE #1
The current in mA for each device is as follows:
- 2 Street Lamps draw 10mA@3V each (each one has 3 small LEDs)
- 2 Houses draw 35-40mA@4.5V each (each with 1 LED)
- 1 Church draws 40-50mA@4.5V (2 LEDs)
- 1 Skating Rink draws between 10-240mA@4.5V (16-17 LEDs, 2 constant, the rest flashing, plus plays music)
Total per circuit:
- 20mA@3V
- 85-330mA@4.5V
UPDATE #2
With confidence gained from suggestions here, I've cracked open each unit.
- The lamp posts with 3 tiny LEDs in each, have a 51Ω±5% inline resistor.
- The houses have no resistors (1 LED in each house).
- The church (with 2 LEDs) has 2 lines to the positive battery post, one without a resister, the other with a 220Ω±5% inline resistor—my guess is this is going to an LED in the tower and dropping the power/brightness a bit for the small space to equalize the appearance of the 2 lights.
- The skating rink has no in-line resistors, but a printed circuit board and speaker.
Best Answer
The simple answer for the houses that run from 3* 1.5V cells is to simply use an off-the-shelf cell phone charger. These are nominal 5 Vdc output. Note that most alkaline cells start off at about 1.6 Vdc but decay quickly down to the nominal 1.5V value.
If you are concerned that 5V is a tad bit too high, simply add a standard silicon diode in series with either lead, making sure to observe polarity. This will drop the voltage down to near 4.3 Vdc or so.
The street lamps are a tiny bit more work - just use more silicon diodes in series with the power supply leads that feed those lamps. Two diodes will drop your 5V power supply down to near 3.3 Vdc.
I think highly of Genuine Samsung cell phone chargers: nominal 5 Vdc at 2 Amps. You even may have some hanging around from old phones. If not, they are readily available from eBay and other sources. Just be sure to purchase Genuine chargers - some of the Asian-made knockoffs are complete trash.