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Welcome to my first instructable. I hope it will make sense.
Electronic circuits tend to have a lot of things in common. It's rare to see a circuit without resistors, for example. However, there is only one thing that ALL circuits share - the power source. Power supplies have become one of my favorite and most common projects. When I was first studying electronics, I needed to test a circuit that seemed to be malfunctioning. I had to build a power supply to do so. Since then, I've needed to build or tweak so many power supplies that I consider them the most practical and useful type of circuit to learn.
Today we're dealing with "Wall Warts." They are those big black bricks that, when you plug them in, tend to cover one or even two neighboring empty sockets. Note that in some cases, the big black brick doesn't plug into the wall itself, but has a cord that plugs into the wall. For simplicity, I will call these wall warts as well. Starting with a wall wart will greatly simplify the project. It also prevents you from having to deal with higher household voltage, so it's a much safer circuit to tackle until you know how NOT to get electrocuted.
Regardless of voltage levels, HEED THIS LENGTHY DISCLAIMER!!! ...
Any discussion about power is incomplete without a cover-my-ass disclaimer. Some of these circuits are very tame, while some involve dealing with the voltage that magically comes from the walls of your home, and can kill you (not so magically). Treat ALL circuits with a high regard to the God of Power. Always assume danger. Even low voltage projects can be fatal. Amperage is the real danger. A mere 10mA (mA = milliamps or 1/1000 of 1 amp) can provide you with parting gifts of severe shock and breathing difficulty. At 100mA, your prize is more likely to be a formal gathering of your family and friends, better known as 'Your Funeral.' As a point of reference, household circuits range from 15 to 20 AMPS (note: that's 15 THOUSAND mA!!).
PARTS: These will vary depending on how you tackle the circuit, so I will discuss them inline with the text and summarize them at the end.
Electronic circuits tend to have a lot of things in common. It's rare to see a circuit without resistors, for example. However, there is only one thing that ALL circuits share - the power source. Power supplies have become one of my favorite and most common projects. When I was first studying electronics, I needed to test a circuit that seemed to be malfunctioning. I had to build a power supply to do so. Since then, I've needed to build or tweak so many power supplies that I consider them the most practical and useful type of circuit to learn.
Today we're dealing with "Wall Warts." They are those big black bricks that, when you plug them in, tend to cover one or even two neighboring empty sockets. Note that in some cases, the big black brick doesn't plug into the wall itself, but has a cord that plugs into the wall. For simplicity, I will call these wall warts as well. Starting with a wall wart will greatly simplify the project. It also prevents you from having to deal with higher household voltage, so it's a much safer circuit to tackle until you know how NOT to get electrocuted.
Regardless of voltage levels, HEED THIS LENGTHY DISCLAIMER!!! ...
Any discussion about power is incomplete without a cover-my-ass disclaimer. Some of these circuits are very tame, while some involve dealing with the voltage that magically comes from the walls of your home, and can kill you (not so magically). Treat ALL circuits with a high regard to the God of Power. Always assume danger. Even low voltage projects can be fatal. Amperage is the real danger. A mere 10mA (mA = milliamps or 1/1000 of 1 amp) can provide you with parting gifts of severe shock and breathing difficulty. At 100mA, your prize is more likely to be a formal gathering of your family and friends, better known as 'Your Funeral.' As a point of reference, household circuits range from 15 to 20 AMPS (note: that's 15 THOUSAND mA!!).
PARTS: These will vary depending on how you tackle the circuit, so I will discuss them inline with the text and summarize them at the end.
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Signing UpStep 1Acquring and testing the wall wart.
As stated, starting with a wall wart will simplify any power supply build because some of the work is done for you. The type of power supply we're working on (called "Linear") has a few tasks to perform before providing us with a usable current. First, the 110 volts of AC from your home outlet goes through a transformer to step the voltage down to a level more common in electronic circuits (usually between 5 to 12 volts). Next this lower AC voltage is then "rectified" by a series of diodes arranged as a "Bridge Rectifier" in to a DC voltage. Finally, a capacitor is used as a filter to smooth out most of the remaining AC pulses (know as "ripple"). These tasks are all done by the wall wart and you didn't need to break a sweat.
To get started, we need to find/test a wall wart. As electronics become obsolete or die, many perfectly good power supplies are left behind. How many old cell phone chargers do you own?
FIND IT: Round up all of the warts you can find and check their markings. You're looking for it's OUTPUT. We want a DC voltage, so make sure the voltage reads VDC (volts DC) not VAC (volts AC). You'll likely see lots of 9 volts, plenty of 5 volts, and a handful of 12 volts. You may see 6 volts, or even 4.5 if you've ever owned a Sony discman. Pick the one that's closest to your intended voltage. 5 volts is ok for a lot of projects, 9 will give you more flexibility. If you want to build a variable power supply (more on that later) 12 volts is a better option. The amperage rating isn't as critical. Pick the highest amperage you have and you'll be fine. My smallest is 300mA, and the only time that didn't work was when I tried to use it to power a digital camera.
TEST IT: The wart will have a plug on the end that you likely don't need. Go ahead and clip it off, but leave a few inches on it in case you want to solder it somewhere else later, or in case you realize you just destroyed the charger to something you actually use! Attach the newly exposed leads to your multimeter. The negative lead will usually have a white stripe or a raised ridge along it. Be sure the leads aren't touching each other and plug in the wall wart. You'll notice the reading is probably higher than the output rating. These wall warts are generally unregulated. Don't worry about it. Just take note of the output. If you're voltage reads negative, swap your leads around, and then tape or otherwise mark your leads for future identification.
To get started, we need to find/test a wall wart. As electronics become obsolete or die, many perfectly good power supplies are left behind. How many old cell phone chargers do you own?
FIND IT: Round up all of the warts you can find and check their markings. You're looking for it's OUTPUT. We want a DC voltage, so make sure the voltage reads VDC (volts DC) not VAC (volts AC). You'll likely see lots of 9 volts, plenty of 5 volts, and a handful of 12 volts. You may see 6 volts, or even 4.5 if you've ever owned a Sony discman. Pick the one that's closest to your intended voltage. 5 volts is ok for a lot of projects, 9 will give you more flexibility. If you want to build a variable power supply (more on that later) 12 volts is a better option. The amperage rating isn't as critical. Pick the highest amperage you have and you'll be fine. My smallest is 300mA, and the only time that didn't work was when I tried to use it to power a digital camera.
TEST IT: The wart will have a plug on the end that you likely don't need. Go ahead and clip it off, but leave a few inches on it in case you want to solder it somewhere else later, or in case you realize you just destroyed the charger to something you actually use! Attach the newly exposed leads to your multimeter. The negative lead will usually have a white stripe or a raised ridge along it. Be sure the leads aren't touching each other and plug in the wall wart. You'll notice the reading is probably higher than the output rating. These wall warts are generally unregulated. Don't worry about it. Just take note of the output. If you're voltage reads negative, swap your leads around, and then tape or otherwise mark your leads for future identification.
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Just one little comment: "FIN" is literally the French word for "The End", it's almost the same than "Thanks for reading" (which translate to "Merci d'avoir lu".
im sorry if im wrong but this is to create a variable voltage power output?
You would not have to change the resistors or capacitors to accommodate different power supplies. This chip and circuit cover a wide range of inputs, just stay within the chips specs. ALWAYS check the chips data sheet to see it's maximum input, and do not exceed it. The data sheet may have variations on this circuit to accommodate various scenarios, and you may find one that is more applicable to your needs.
As a rule, always use the components listed in the schematic on the chips data sheet (unless you understand the concepts enough to know the implications of changing them). Not only will it be safer, but the chips manufacturer will have done testing to find the most efficient arrangement.
Check out this website for some of these 'concepts' I mentioned:
http://electronics.wisc-online.com/
The left sidebar has many educational subsections dealing with more concepts than you can shake a resistor at.