alternating current square wave induction circuit


Im very new to electronics so apologise for novice questions i'm experimenting with induction coils as a hobby and seeing effects on different metals and things im after a simple circuit that will flip voltage from +voltage to - voltage as im trying to create a high frequency fluctuating inductance and would like it to be more like a square than a sine wave as i want the flip to be more immediate i don't have any specifications or anything yet

is there an existing circuit that i am referring to that would help my discovery?

thank you

by devid3an
November 27, 2016

Sounds like you're trying to make a square wave oscillator. Two big questions: (1) How fast are you trying to make it oscillate (what frequency)? (2) What do you want it to drive (how much current at what voltages)? From there we can probably help you.

by mrobbins
November 27, 2016


thanks for your quick response yeah square wave oscillator, sums up exactly what i am trying to create. This is going to be pretty vague as i don't really have specifications to work with I would like to power it from a 12v DC or 24v DC source if possible. as its for experimentation hobby purposes only, as high frequency as possible preferably variable so i can experiment and high voltage as possible, but what ever is easy as its only an experiment purposes just something to get started with really. Coil size/components i havn't got any preference - sole intent to create a high fluctuating inductance state. hopefully thats enough for someone to give a circuit a crack :)

by devid3an
November 27, 2016

2 Answers

Answer by mrobbins

Here's a way to do it with two ICs:

1) Use a 555 timer to create the square wave timing signal. See this oscillator circuit. You can make R2 be adjustable (with a potentiometer, for example) so you can control the frequency. Example part number LM555CN.

2) Use an H-bridge driver which is capable of outputting both high and low voltages, and is tolerant of inductive loads. Example part number L293DNE.

Here's a schematic:

M1 and R3 form a simple inverter so that outputs 3,4 of the h-bridge are driven with the opposite signal as outputs 1,2.

Note that the 555 isn't rated to operate above 16V, so you should power this from 12, not 24 volts.

You could also use a hex inverter chip, like a 74HCT04. This could replace the 555; you can use it to make a square wave oscillator with just a resistor and capacitor. And use one of its inverters as the inverter for the 3,4 side of the bridge drive, so you wouldn't need M1 and R3. But now you would need a 7805 style voltage regulator or similar for your logic.

+1 vote
by mrobbins
November 27, 2016

Answer by mikerogerswsm

Another way would be to buy a function generator kit and build it. Most cover a few hertz to several hundred kilohertz and provide a reasonable output. Adding an audio amplifier built from a kit would produce greater output up to about 20kHz.

+1 vote
by mikerogerswsm
December 09, 2016

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