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Transformers
Posted by Rockinriley14 on 4/3/2004, 7:28 pm I am constructing a small model transformer for a project I am doing. the transformer I am building will run off of pulsed DC power through a power transistor with a 555 timer controlling it. It does not have to be very powerful at all, but a homebuilt transformer. The transformer I built is on an E-core of laminated steel i found in my junk box. It is about 1 1/2 inch high. I put two windings on a small square piece of plastic that fits onto the center pole of the E core. The windings are side by side, one has 150 turns, the other has 300. I want to take 12v down to 6v. i hooked up the transformer to 25v ac with no results of power. I had the 300 turn side hooked to the power and the 150 turn side hooked to my voltmeter. i got no reading of power. The transformer is wrapped with about 26 gauge magnet wire or so. (i pulled it off of some ignitor thing) Please help me with building this transformer! Thanks in advance
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Re: Transformers
Posted by Bert Hickman on 4/3/2004, 8:14 pm, in reply to "Transformers" Hi! Designing transformers can be a bit tricky. The key is to insure that you have a sufficient number of turns on the primary for the size and type of core you're using, that you drive the transformer from a source of AC (pulsed DC may cause problems!), and that the core has a good magnetic circuit. If you are using a single transistor to drive the transformer, you may need to connect a capacitor in series with the transformer's winding in order to prevent the average DC voltage of pulsed DC from quickly saturating the transformer's core and possibly burning out your transistor. An alternative is to use a center tapped primary - feed DC into the center tap and alternately drive the ends of the primary from a pair of transistors in a push-pull configuration. Regarding the core's magnetic circuit, I assume you replaced the "I" portion of the core or interleaved the E laminations in order to complete the core's magnetic circuit. We don't have the space on this board to cover the details of transformer design. However, here are a couple of excellent sites that cover the step-by-step process of designing your own transformer - everything you wanted to know but were afraid to ask: Best regards, -- Bert --
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