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easy way of converting dc into ac Answered

does anybody know of an cheap simple circuit, using only a few components, to convert dc into ac or pulsed dc? I'm going to be using a super capacitor that's rated for 2.5 volts and I want more out of it, so the output is going to be put through a voltage multiplier circuit.

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tech-king

10 years ago

id say hook them up in parallel. i have no idea about different transistors, but i do not think the 2n2907 is interchangeable. i tried that on another science project, and got poor results. you could ad a V multiplier. the one below is a multi-stage cascade, so you can simply add more stages to it. unmodified, its an 8x multiplier. ignore the text, its from the 4x multiplier. the smaller the capacitors are, the more ripple there will be in the circuit.

instructables.jpg
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guyfrom7uptech-king

Reply 10 years ago

Ok, that's what I was originally going to do, I'm going to buy a bunch of the transistors and have a bunch of trial and error, I'm going to try and not use the transformer because What I need to build has to be light, and simple. Also the bigger the capacitor means more amps? This is meant to drive a motor (+ gain more knoledge on ac circuits), I'm just seeing if I can power it off of this, if not I'll go back to a more complicated dc-dc converter.

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tech-kingguyfrom7up

Reply 10 years ago

the lower the value of the caps, the more ripple in the circuit. you could either use large, high value caps to keep ripple low, or use an inductor (choke). the more ripple, the closer to an AC sine wave the circuit is.

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guyfrom7uptech-king

Reply 10 years ago

so size of cap doesn't matter for amps? I'm goingt o use the smallest caps then!

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tech-kingguyfrom7up

Reply 10 years ago

as long as the caps are rated to the voltage.

small caps=lots of ripple.

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guyfrom7uptech-king

Reply 10 years ago

I want to thank you sosososo much for all of your help!

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tech-king

10 years ago

yo probably could hook it directly, but id go with the transformer for isolation purposes. as you may or may not see in the picture, DO NOT touch the wires on the secondary side of the transformer. plus, the transformer is a stock one, not one that needs to be re-wound.

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guyfrom7uptech-king

Reply 10 years ago

ok, I might make my own tiny toroid wound transformer because this thing has to be really light. Do you know at what frequency this schematic operates at? Can it be adjusted?

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tech-kingguyfrom7up

Reply 10 years ago

I'm not sure. i just fried my last 2n2907 20 min ago, so i have no way to find out (until tomorrow anyhow). however, its a high enough hz to power a fluorescent or neon lamp.

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guyfrom7uptech-king

Reply 10 years ago

sweet, if I want more power should I hook up a couple in paralell or just use better transistors, would any npn & pnp transistor work?

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tech-king

10 years ago

this is a pretty simple dc pulse unit. its hard to tell, but the cap is .1 uf, the resistor 27k, the transistors 2n2222 and 2n2907. the line going up the top is power in, and the circuit is rated for 1.5 to 9 dcv. the transformer is anything from 120 to 63 v.

iroda solderpro 35.jpg
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guyfrom7uptech-king

Reply 10 years ago

now that's what I'm talking about! Are the transformers nessesary?

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guyfrom7upguyfrom7up

Reply 10 years ago

I mean is the transformer nessesary? can I hook that directly up to a voltage multiplier?

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guyfrom7up

10 years ago

so there's nothing like 1 or 2 componenet circuit? I think I might have to go with the 555 circuit, it's just that space is a factor.

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Goodhartguyfrom7up

Reply 10 years ago

well, if you are good with surface mount stuff (I personally can't see that well anymore), you can save a lot of space that way (except for the transformer and the 1 uH coil).

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guyfrom7up

10 years ago

The ones that Goodhart are okay, but is there a circuit that's so simply that it can be just like a resonator or ossosilator (I don't know what they do or have ever used them, but just by looking at the name it must be related) and a power transistor?

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tech-king

10 years ago

what about high voltage dc pulses? i have a circut i can post later if pulses are okay. plus it works off a battery

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guyfrom7up

10 years ago

anyway, back to the original question, is there an easy way to make pulsed dc or ac from a dc source?

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Goodhartguyfrom7up

Reply 10 years ago

Just be careful if you decide to build that last one, it can deliver a lot of power.

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guyfrom7up

10 years ago

thanks for the link, I just found a 50F capacitor on mouser for $6.54, it's rated for 2.3volts and I'm going to buy it.

Does anybody else just love the thought of super capacitors but don't know what to do with them?

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Goodhartguyfrom7up

Reply 10 years ago

I have a few 1,000 uF caps and a ONE farad cap. I can get ibit of a wild pop from those ;-)

PS: I know I wrote this before, but I love EDN as a source. I used to get their mag.

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guyfrom7upGoodhart

Reply 10 years ago

this 50F cap is going to be like a battery though, and my biggest capacitor currently is are 4x 100 volt 33,000uF capacitor, capable of arc welding :)

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Goodhartguyfrom7up

Reply 10 years ago

yeah, sorry about that, I misplaced the comma, I meant I do have a few 100,000 uF caps around and one 1 farad cap that I am actually a little overly cautious about using :-)

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guyfrom7upGoodhart

Reply 10 years ago

that makes more sense, that's a pretty big capacitor! Originally i thought, wow, only 1000uF? That's usually the minimum for smoothing! Have any ideas for what to do with a 50F, 2 volt capacitor?

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Goodhartguyfrom7up

Reply 10 years ago

Some people use them in their audio systems: Audio capacitors

I have heard of the following being done, but haven't seen the specs on it yet: A small capacitor-based DC power supply was designed using a combination of bootstrapped and non-bootstrapped converter topologies. This design focused on start-up under load, low voltage performance, maximum energy-density and utilization of surface mount components. These were integrated onto a board mounted on configurations of 50 F, 2.5 V ultracapacitors

Or Robot controller power supplies....

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guyfrom7upGoodhart

Reply 10 years ago

hmmm... interesting, what's the whole italitized thing for? Just a power supply for something like a computer, or something like a car? Robot would be cool