Minitronics sells 1.5 volt DC lights but they no longer sell the wall wart power supply for them. What can I use to power these lights?
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You can use a higher voltage power supply and then use diodes to lower the voltage. You can also run the lights in series on higher voltage as well.
The series option is the easiest way to deal with this.
bmoran4 posted:You can use a higher voltage power supply and then use diodes to lower the voltage. You can also run the lights in series on higher voltage as well.
Diodes or resistors?
Steve
Diodes, not resistors. Diodes have a flat voltage drop with differing current, resistors will vary the voltage drop based on the current.
How do I know what size diode to use? Is there a chart or rule of thumb to calculate voltage drop? If I use a 3 volt wall wart or a 12 volt transformer what diode would I use? Where is the best place to purchase them? All electronics , radio shack?
A silicon diode drops around .7 volts. You can use any current rating, that depends on how much power you're drawing. Remember, a transformer is AC, so different rules may apply.
Take the 3V wall wart example. First, you have to make sure it's a regulated wall wart, of all bets are off. For 3V, to get to roughly 1.5V with diodes, you'd use two diodes in series with one lead.
If you're not comfortable messing with diodes (or resistors) to drop the voltage, consider a DC-to-DC regulator module. The module takes DC voltage in (2-wires), and converts it to a settable DC voltage out (2-wires). For just over $2 you can get one on eBay (free shipping from Asia so patience required) that even has a built-in LED voltmeter so you can dial in 1.5V or whatever.
The input DC can come from a DC-output wall-adapter/wall-wart you may already have lying around. The module performs regulation so the DC-input voltage can be a 5V, 12V, or effectively any common wall-wart DC voltage.. and the output is regulated to the settable voltage irrespective of the input voltage.
In the photo above, the 4 bulbs are drawing about 470 mA (0.47 Amps) driven by 1.5V DC. I noticed on the Miniatronics website that they sell various 1.5V bulbs. The ones I saw said they draw 25 mA or 30 mA each. All modules, diodes, resistors, etc. have their operational limits in Volts, Amps, Watts, whatever so there is some do-the-math. There are many guys on OGR who will assist in this department if not in your comfort zone. Obviously a key piece of the puzzle is how many bulbs you plan to drive.
Many wall-warts use a barrel or coaxial style connector. There are low-cost adapters to convert this to screw-terminals so you don't have to splice the wall-wart cable. Here's an example photo from a previous OGR thread showing a typical DC wall-wart and the connector adapter:
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Thank you , I ordered the LM2596 converter, power supply and adapters today.
