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What's the Difference Between Watts, Amperes, and Volts? Answered

I always find this really confusing. Also I have a MotoMaster 12v solar panel supposedly for a car or something from Canadian Tire but I got it for electronics projects. I can get a voltemeter to detect voltage coming from it but I can't get it to work a motor or light or anything. It has two normal alligator clip leads.



Reply 11 years ago

What's the difference between a multimeter and a voltmeter? I don't have a clue how to use either, but I have at least two (of either kind, i dunno. One from a science lab kit for homeschooling and my dad has one)

They are generally the same thing. Technically, a voltmeter only measures voltage. A DMM-Digital MultiMeter-measures AC and DC voltage, AC and DC current, resistance, and continuity of diodes. A VOM-Volt-Ohm Meter-is used for the older analog meters, which do the same thing, but with a needle instead of a digital readout. An analog meter is useful for many things, but they can be finicky to use and are hard to find. Do you have one of either? You can probably get your dad to explain how to use it.

Hmm. Looks like I have a VOM-Volt-Ohm Meter and a DMM-Digital Multimeter. My dad doesn't know how to use either.

Try Googling keywords such as "multimeter tutorial", "meter tutorial", and such. You can get some nice basic tutorials and how-tos. Maybe I'll make an Instructable later...
And now I have the rights to that, as I have declared my idea this fifth day of May, the year 2007 C.E., at 0257Z! Hahahahaha! All MINE!

Go to it! I was thinking of doing something along those lines, aimed sorta at the LED crowd ("measure voltage and current using cheap DVMs.")

Here's a fairly good explanation of the water model for electricity. Voltage is like the water pressure, it allows the water to travel farther. Likewise, long-distance power lines carry thousands of volts. Amperage is like the total amount of water flow. You need a larger pipe to carry a lot of water flow, and you need heavier wire to carry more amperage. With solar panels, you are probably drawing more current than the panel can put out. You'll be lucky to get a 100mA 12V muffin fan to run unless you live on Mercury. These solar panels theoretically trickle-charge your car's 12V battery if you park in the Sahara, but they don't generate much power.

How powerful is 1.8 watts then? The solar panel was 10 bucks, on sale from like 30 or something. I thought I could use it for electronics....gah!

At 1.8 watts, it should work. As explained below:

1.8W = 12V * I (or) I = 1.8 / 12V

Current (I) equals 0.15A or 150 milliamps. 1/10 of that current should be enough to light an LED (and fry it, @ 12V.) Most modern microcontrollers need less than 5 mA (some much less.) Motors? Well, small ones should work.

But since most ICs run at 5V or less (and LEDs @ ~3.5V or less), you'd probably loose a good bit of the current to a voltage regulator (unless you spend a bunch o' cash for a switching reg.)

The solar cells are likely wired in series to produce the 12V output. If you 'feel lucky,' you might be able to rewire the cells in parallel @ a lower voltage. You'd get more current from that, and wouldn't loose as much to regulation.

Check it in sunlight with a multimeter to see the voltage and amperage. This will drop drastically under load. Put a reply on what your results are. Also, what kind of light/motor are you using? As for the light, are you sure it isn't lit but it is invisible in sun?

Cuz I have a little 3 volt solar panel about the size of a playing card and it can power a small 2 cm diameter motor.

Voltage times Current (amps) = power (watts)

I would think it would be able to power a light if it was able to power a car