Circuit part that adjusts frequency of A/C current.?
I m trying to build a circuit for a kind of science project. I simply need to be able to adjust both the amperage and the frequency of an A/C current. Adjusting amperage is easy. Adjusting frequency I m totally lost on. I need to adjust the frequency between 0 and 70 hertz. The current never exceeds 5 milliAmps,...
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answers:
Markus Imhof say: You'll need a variable oscillator. Like already said, the required voltage and waveform are about as important as the current - and the information whether you need true AC (i.e. symmetrical to 0) or simply oscillating between 0 and 100%.
A 555 timer has been suggested - but I would consider that to be last century, and too much effort. Easier to use an Arduino (Nano) - especially since, with a few tricks, you could do all kinds of waveforms at these low frequencies.
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Lisa A say: Nope. You need a variable resistor.
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Crazy Horse say: As an ex school physics technician, I can tell you what you need is to go to your physics teacher and ask to borrow a signal generator, preferably one that will allow you to alter the frequency from : 0-70 Hz as you require.
You say ac, but ac does not necessarily mean a sine wave, it could be any wave that reverses the flow of current in the load It maybe that a sine wave is what is required or it could be that it does not matter. You are expected to use what is available and not necessarily make it. A signal generator from the physics lab should be able to supply three types: sine, square and triangular- take your pick.
A 555 timer as has been suggested by another contributor is not truly ac. Yes, you will see the voltage level alternate; but, you will never see it go negative as in a true ac waveform (use a scope to find out). Of course, it all depends upon what YOU ARE MEANING by ac, and just maybe the 555 timer circuit will do the trick for your project. If you want to e-mail me the details of your project I may be able to help further and see what is really needed.
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lee26loo，異域秦後人 say: TO VARY SINEWAVE REQUENCY IS NOT A EASY TASK AS YOU THINK. 60C/S AC POWER CANNOT BE VARY DIRECTLY INTO 0-70 Hz. IT NEEDS TO GO THROUGH A COMPLEX CIRCUIT....
AC POWER ---> CHANGE INTO DC POWER ----> POWER A VARIABLE SINE WAVE OSCILLATOR -----> POWER AMPLIFIER
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Joe say: What you need is called a "function generator". Google that term, and you'll find a bunch of ICs, kits, or finished products that will do the job.
Most can output a sine wave, triangle wave, or square wave. If you're building from an IC, just a few external components will let you tune the frequency to what you want.
Add a transistor amplifier to get the voltage and current you need.
This is not hard. Google "function generator".
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qrk say: You're missing information. How much voltage do you need? How much current do you need? What's the lowest frequency you really need?
Zero frequency is DC. That's a separate device. If you need to generate AC mains voltage, there are variable frequency power supplies for testing power supplies. These are generally expensive, even on ebay.
You could build your own frequency generator. You can use a 555 timer and a flip-flop to create a 50% duty cycle. Then, you need to amplify it and possibly filter it to turn it in to a sine wave. What sort of voltage do you need? You could feed a power transformer backwards if you need to generate 120VAC with a suitable power amplifier, but you will be limited to 40 or 50 Hz on the low end due to core saturation of the transformer.
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bqivc say: icqzydnk
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