We can make it out of individual discrete diodes or use one that is purpose built. That's where the bridge rectifier comes in, and in this case a full-wave rectifier. In order for electronic circuits to work, we must convert this stepped-down AC voltage to a flat, stable DC voltage. The only way to do that is by using AC current, which switches between positive and negative voltages at 50-60Hz. The only thing is that the output is always AC, since for the magnetic coupling to work, the magnetic field must change polarity. This is very efficient and space saving, especially since you can add several separate windings to get whatever voltages you want out. Since the two windings are both made using insulated wire, you can wrap one around the other, with both wrapped around the core. Adding a magnetically permeable core between the two greatly enhances the effect, reducing loss. If another coil is placed nearby, along the same axis, the magnetic field will induce a current, and thus a voltage, in the second coil. When a current is introduced through one winding (or coil), it creates a magnetic field, with poles forming along the winding axis. The number of windings determines how much change in voltage you will get out.
Each winding can be any where from a just a few to several thousand turns. A large part of the weight of the device is actually the transformer itself, which is usually made of several steel plates sandwiched and then epoxied together, and two or more windings of coated copper wire. Others have the conversion circuitry built inside. Some have a big, black, hurky wall wart that is unsightly and nearly impossible to plug more than one into a power strip without taking up two or three slots each. Most consumer electronics regulate the AC mains to DC. Don't ever get comfortable or complacent with things that can seriously hurt you. When you get to the point where you feel comfortable, stop and do a mental check. Only you can know if you should proceed or not. That being said, I am not responsible in any way for anything that you do. I only work with mine in my office with the door locked so the kids can't physically interrupt me. Make sure that your workstation is either isolated from other people or that they are fully aware of what you are doing. I'm not trying to downplay the dangers involved. This Instructable is meant to help overcome the anxiety that comes with working with AC, but don't think that I don't get the chills every time I plug in the cord so I can test the circuit. AC MAINS VOLTAGE IS EXTREMELY DANGEROUS!!! You must be extremely careful. Hopefully I can dispel that fear with this Instructable.īefore we begin, a word of caution. The problem is that it's AC, and most people are understandably nervous about working directly with AC mains. That required rectifying and regulating the 120VAC mains to a stable 9VDC. I also don't want to have to open the box every time the battery dies. Since I was wanting to have the switch open a relay to allow AC current to pass through, it made sense to me to make the timer circuit inside utilize the AC power that was already there. One example is the Motion Activated AC Switch that I built. Every once in a while I come up with an idea for a circuit or device that has applications where a battery may not be the best or most convenient option for a power supply.
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