Electronics > Beginners
Homemade Transformer
Zero999:
The only reason to build your own transformer is when you need custom output voltages which you can't get from a ready made unit. You can buy transformer kits but they work out more expensive than just buying a transformer.
It's also possible to rewind some transformers. I've rewound cheap wall wart transformers which have the iron laminations weakly bonded together. I prise apart the laminations, rewind the secondary and glue the laminations back with super glue.
Armin_Balija:
--- Quote from: Hero999 on July 05, 2011, 04:15:18 pm ---The only reason to build your own transformer is when you need custom output voltages which you can't get from a ready made unit. You can buy transformer kits but they work out more expensive than just buying a transformer.
It's also possible to rewind some transformers. I've rewound cheap wall wart transformers which have the iron laminations weakly bonded together. I prise apart the laminations, rewind the secondary and glue the laminations back with super glue.
--- End quote ---
I tend to stay away from rewinding transformers just because I've been told that they're made to work at certain frequencies.
Zero999:
You're generally safe as long as you only rewind the secondary coil which is easy on most mains transformers, as it's normally on a separate bobbin.
ejeffrey:
--- Quote from: Armin_Balija on July 05, 2011, 04:21:52 pm ---I tend to stay away from rewinding transformers just because I've been told that they're made to work at certain frequencies.
--- End quote ---
As far as operating frequency goes, that is mostly set by the core. You can rewind a transformer with new secondaries to generate different voltages with no problem. For RF transformers, skin effect in your copper is important, but for line frequency (and most audio applications where the current is low), you just need to wind the right number of turns with a gauge that has low enough ohmic losses for the power you want to draw (not exceeding the original power specification).
One thing that is often useful to do is to add windings to a transformer. For instance, you can add a low-power 15 volt winding to an amplifier's power transformer to power a preamp or other small electronics.
mishimaBeef:
I don't understand what all the fuss is about. Fusing the primary is a good precaution isn't it? Also, isn't the household wiring protected by a 15 A circuit breaker and then fuses downstream from that?
Why is wiring the secondary so much less trouble than wiring the primary exactly?
Part of the reason I'm doing this project is to gain insight into the transformer as a component and all the physical relationships that play a role in its operation.
To the comment about making my own resistor and capacitor, I do intend to at some point for the same reasons as this project. Am I going to build every capacitor and resistor I ever use? No. But I do wish to gain deep insight into the electromagnetic principles at play in our everyday devices.
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