Step up or step down voltage?

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Old 07-12-16, 08:19 PM
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Step up or step down voltage?

I have a bunch of devices that I need to use, but the power source is at 12 volts. Where do you guys get your components (preferably inexpensive) for little projects like this? Unfortunately, the devices use all sorts of different voltages, from 5 volts to 20 volts. I'm also new to electronics, but can solder.

I imagine I just put some sort of resistor on the at the live wire to step it down?
 
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Old 07-12-16, 08:29 PM
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You could use a variable DC power supply. Examples: https://www.amazon.com/s/?ie=UTF8&ke...l_2169s4lx21_b Or build one. Example: Variable DC Power Supply for <$15
 
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Old 07-12-16, 08:49 PM
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Not really what I was looking for. I know exactly what the voltages and amperages of the devices are and those devices are not going to change any time soon.

Also it looks like, based on the YT comments, that this is only for 1 AMP. I will be drawing just under 200 watts, with some devices drawing as much as 90 watts each.
 
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Old 07-12-16, 09:31 PM
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We can better help you if you give us the details on what you are trying to do.
 
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Old 07-12-16, 10:39 PM
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Also, I'll need an enclosure. Have you guys ever used legos for this? Any interesting ideas?
 
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Old 07-14-16, 06:18 PM
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A resistor will not work unless the device draws an absolutely steady constant current at all times when operating.

The number of volts dropped by the resistor at any given moment always equals the resistance times the number of amps being drawn.

Even so, the resistor will dissipate as heat (and waste) the electrical energy representing the volts you wanted to drop leaving behind the volts the device wants. The resistor must have a wattage rating sufficient for this. Watts to be dissipated equals voltage dropped times amperes flowing.
 
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Old 07-14-16, 06:50 PM
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I have a bunch of devices that I need to use, but the power source is at 12 volts.
Are you trying to power multiple devices powered from car or some other 12V power source?

Resistors won't work as AllanJ said. Resistors are only good for low steady current devices (such as LED).
You will need switching power supply circuit and it is quiet complex to build on your own.
Easiest option can be purchasing DC powered 19V laptop power supply (something like one in your link, but I would recommend bigger unit.) and using variable step down DC to DC converter.
However, most cheap variable DC to DC converter (such as LM2596 module you linked) doesn't have very accurate and stable potentiometer thus output voltage will not be very stable and will change with a little shock.

I suggest replacing potentiometer with 1% metal oxide resistor to output fixed voltage for voltage sensitive devices.
You may also choose to replace potentiometer with multi turn high accuracy potentiometer, but those aren't cheap. You will also want to add a volt meter (cheap segment LED ones on ebay work fine) so you can see what voltage you have set.
 
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Old 07-14-16, 06:55 PM
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No...you don't want to use resistors.

That laptop charger is a bargain. That charger is not reducing voltage.... it's increasing it. That takes a DC to DC convertor. You aren't going to be able to replicate that easily.
 
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