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need help winding toroidal transformer

I'd like to know how to wind a torodial transformer with a toroid that I just happen to have. I would like it to work at 60Hz at 120 volts (US mains) and have an output of 36volt centertap (18-0-18) or maybe a little less (I'm building an op-amp powersuppply that gets regulated to +-12volts) and as many amps as possible (well, safely). The toroid I have is painted a light green with a blue ring on one side. it is 1.25" outerdiameter, 0.75"innerdiameter. It's 0.5" thick. It looks like the bottom left toroid in the picture below, just bigger and no wire. I do not know what gauges to use, how many windings (well, I know the ratio), how many amps it can deliver, how I should wind it, etc.

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Big Bwana9 years ago
At 60 Hz you won't be able to wrap the secondary, so never mind the primary, those toroidal core you have might be good enough to build a Switched mode power supply out of that has 120 volt input and 18-0-18 Volt output but the switching frequency would be high then 60 Hz (( some where in the high kHz are to low MHz area And then you only need a few wraps of wire and you can greatly reduce the size of your magnetics.......
guyfrom7up (author)  Big Bwana9 years ago
That might be a solution, I'll look into switch mode power supplies, cause I need to get this circuit as small as possible.
Ok so your line powering an op amp, what sort of current are you looking for ? there is lots of wal-wart switched mode supplies and there is even small 15-0-15 ones out there the produce 85 watts in a 3 inch by 2 inch by 3/4 inch package.... But if it's just a small op opamp you only need a few mA's and you could use a online supply which is nothing more then an Zener diode cap and resistors, and very small, I built a 5 volt one that fits inside an extension cord end to light it up with blue LED's....
guyfrom7up (author)  Big Bwana9 years ago
well, here's the whole situation: I have a op-amp in a wein-bridge setup creating a 10MHz sinewave (the opamp needs +-12volts) I need to take that output and amplify that so it has more current and voltage (maybe a total of 25 watts out?) This amplified output will be driving a tank circuit (I'm trying to make a wireless electricity device) I need a power supply to deleiver all of the energy
How's your radio theory? (mine sucks.) You're essentially building a high power radio transmitter, which has technical, safety, and legal issues well beyond those of normal circuits...
guyfrom7up (author)  westfw9 years ago
well, the lowest radio waves in use are like 29 MHz, and that's for toys. You know that wireless electricity machine that MIT made? It works by resonance (with a tank circuit) and it operates at about 10MHz. saftey issues, all the power that isn't used get's reassorbed into the tank circuit. legal issue... I don't think that's a problem
Ah, your radio knowlege is worse than mine. A bit of searching on wikipedia shows that AM broadcast radio goes from about 0.5MHz to 1.6MHz, with 10MHz being smack in the middle of the frequency range known as "shortwave." In theory, 10MHz is between "bands", but the "most heavily used band" stops at 9.9MHz...
westfw westfw9 years ago
And the safety issue has to do with some of the radiated energy ending up "getting used" to cook your tissues rather than ending up in the target circuit. See "RF burn"; a things that starts to be of concern in the 100kHz range...
is that how Nikola Tesla died,crouched in a corner afraid of the naysayers and the,the wolf?
And there is octaves, 81 of them, so if your not careful you'll annoy more people then you think, and this can include law enforcement, search and rescue personal, and they have the ability to find you, they have found people using low cost DVD players emitting 121.5 MHz which was an octave of is clock speed, much lower then 121.5 MHz and with no shielding it was picked up by search and rescue..... (( radio it's tons of fun and lots of math and shielding )) And as of Feb 1, 2009, Sarsat will no longer uses 121.5 MHz for emergency beacons
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