![]() This voltage will be AC, too, so you'll want to rectify and filter it with caps, depending on its amount, you might need to rectify it, but it should be detectable - you would have to experiment with it. When it is "on", the coil should generate a low voltage that you can measure. Pass one leg of the 24 VAC line through the coil. Make a small coil on a form (like a soda straw or a piece of a plastic ball-point pen body), wrapping say 100-200 turns of 20-24 gauge wire around it. Something you could try, though, would be to detect voltage indirectly by a coil around one of the 24 VAC wires. The regulator would need to be matched to the output of the transformer, so that it will work (for instance, if you were using a 7805 for the regulator, then your output of the rectification would have to be 7 volts or greater, because the 7805 has something like a 2 volt dropout, IIRC). What would be better would be to remove the transformer from such an unregulated wall-wart, then build your own step-down rectification system, then place a small regulator after that (with appropriate capacitors and such - they -are- needed). If it is a linear un-regulated wall-wart, it may work, depending on its design. If it is a linear-regulated wall-wart, then it probably wouldn't work, either. It really depends on how the wall-wart is designed if its one of the newer switched-mode supply wall-warts, then no, it won't work. If input is 120V AC and output is 6V DC, would 60V AC yield 3V DC? if that's the case, 24V AC would yield a little over 1V DC. My question about the wall warts was whether the output was just a function of the input or if it was only a specific voltage. I have a separate power source, sorry for the confusion.Īs stated before, you can't do this directly. I'm trying to send 24V AC to an Arduino digital in. With one of the industry’s broadest technology portfolios, ST's products are found in today's most innovative electronics solutions. ![]() STMicroelectronics Products and Applications - STMicroelectronics Here is some info on power supply design that google turned up. Normally, you'd also have a second capacitor after the regulator to further smooth out the ripple. The voltage regulator knocks the voltage down further to the value you really want and further smooths out the imperfect output of the capacitor. The capacitor fills in the gaps, but not perfectly. The output of a rectifier is either just the positive halves of the sine wave (half-wave rectifier) or the positive half and the negative half flipped over (full-wave rectifier). The 24Vac may push the limits for input voltage on many small regulators though.Ī voltage regulator and a capacitor are not the same. You can fairly easily build a small power supply with a bridge rectifier, a few capacitors, and a small voltage regulator.
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