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From: Kari Laine on 14 Mar 2010 13:13 Bob Masta wrote: > On Sun, 14 Mar 2010 15:32:55 +0200, Kari Laine > <klaine8(a)gmail.com> wrote: > > Hi, Kari! > > I would encourage you to start out with simple > linear regulators and use heat sinks. But as > Pimpom notes, there probably won't be enough > headroom to get 12V DC, at least under much of a > load, from this transformer. Ok I will do that. I have a look what the local supplier has. > > You can get an idea of the transformer's actual > regulation by measuring its output with a > resistive load. Better yet, you can build the > rectifier and filter stage (which you will need > with whatever transformer and regulator you end up > with), and measure the output voltage from that. Yep this is good advice. > If you want to pull (say) 1 amp at 12 volts, then > the load resistor would be 12/1 = 12 ohms, and it > would have to withstand 12 * 1 = 12 watts. If you > don't have a 12 ohm, 12 watt resistor, try a > parallel combination of 10 x 120 ohms, etc. If you > only have 1/4 watt resistors, this would give only > 10 * 1/4 = 2.5 watts. That's probably good enough > for a quick test. Have the meter reading the > unloaded output voltage, then momentarily shunt it > with the parallel array, read the meter, and > remove the shunt, all in a second or so. (Watch > your fingers... may get hot!) For a test like > this, you can increase the resistor power rating > enormously by submerging it in an oil bath. (At > these low voltages, a water bath would also work > fine, but I hesitate to suggest that... a water > bath on the benchtop is not a really good idea!) Ok thank you! This is how to make sure what the supplied voltage is at certain current. I think I have those power resistors somewhere - will have to dig... > If the loaded voltage will still give enough > headroom for your regulator, go for it! If you > want to try anyway, look for "low drop-out > voltage" regulators. (I don't have a part number, > sorry.) Or, you may want to test at (say) 0.5 A > and if that works you can at least get started > with the transformer you have. Yep I got the transformer for free and I think those regulators are not very expensive. I think the housing of the gadget will cost more. > > Also, note that most linear regulators come with > current limiting as a standard feature. Yep. Thank you Bob, which reminds me that I will order the Daqarta now. What I have had little look on it. It is very nice and the help is superb! For everyone needing only audio frequencies price and quality can't be exceeded. And for a hobbyist learning electronics it is nice tool until one knows what kind of an "real" oscilloscope one needs later on. It is great to learn what one can do with an oscilloscope. Schools should be interested - it is quite a difference to blow up a $5 sound card than $5000 tektronix :-) Or have I gotten something wrong ? > DAQARTA v5.10 > Data AcQuisition And Real-Time Analysis > www.daqarta.com >Scope, Spectrum, Spectrogram, Sound Level Meter > Frequency Counter, FREE Signal Generator > Pitch Track, Pitch-to-MIDI > DaqMusic - FREE MUSIC, Forever! > (Some assembly required) > Science (and fun!) with your sound card! -- PIC - ARM - DISPLAYS - RELAYS - MODULES - CONVERTERS - I2C - SPI - KEYPADS - ACCESSORIES http://www.byvac.com (I am just a satisfied customer) |