Voltage Doubler for Wind Generators

I built this circuit in hopes that the wind generator i'm working on will have less rpm's to spin to get the voltage I need to charge batteries or run lights on wind that blows. It's a really simple circuit that has only a few components, mainly a rectifier to convert the a/c voltage my stepper motor makes to dc voltage, and some capacitors to boost the voltage and stabilize it on the output.

I bought this stepper motor at the scrap yard here in Vegas for $3. ( it can be seen further down the page) It's about the size of a small car starter and produces 2 phase a/c output. Just giving it a quick spin, each phase put out about 5 volts a/c. I put a 12 volt LED on one phase and gave it a spin and it barely lit up with the low a/c voltage. I found out I can put the 2 phases in series and double my output there so in doing that I got about 8 - 10 volts a/c with some finger spinning. so putting that through a rectifier as is would give me about that in dc, maybe a little less which is ok probably but we can do better.

Step 1: Supplies

All that's needed to make this voltage doubling circuit is a rectifier (full wave preferred). I got mine from a burnt out computer power supply. The two in the picture came from the same power supply and the specs rate them at 6 amps. I don't anticipate the generator making that kind of output but who knows and we'll see. haha. I also got some caps of a good capacitance.

parts needed:

1 rectifier

3 2200mfd caps 35 volt rated

1 3300 mfd cap 35 volt rateds

1 breadboard

some wires

solder iron and solder

Step 2: Assembly

Placement of the components is key to an easy assembly. I didn't want any jumper wires or massive solder lines so I used the long leads of the caps for all the underneath connections and it worked out great. I put the rectifier in the middle more or less and I wanted the caps on the outside.

Step 3: Follow Schematic and Solder

The two blue caps are for the a/c input and are the 2200mfd's. They are polarized but since its a/c voltage I don't think it matters too much. I ran this through the multisim circuit software and it didn't matter so I think i'm ok. The caps on the a/c side are in series with the circuit, meaning one cap per wire. so solder one wire to a leg of the cap and then solder the other leg to the rectifier a/c input leg. Repeat for the other cap to the other a/c leg of the rectifier.

If you just had the circuit done from this point and put the output wires on the rectifier it would be the double voltage yes, and it would probably work BUT, it wont be a true horizontal dc voltage wave. At this point its a half wave going from 0 - 24 volts and repeating on the o-scope. This is why I added the caps on the output. They make the wave a nice straight dc line. I put the two caps (2200 and 3300 mfd's) in parallel to give me 5500mfd's. It's up to you what capacity you want here, I figure the more the better. anyways, solder them in parallel to each other then solder them in parallel to the rectifier meaning all positives to positives and all negatives to negatives. lastly solder a positive wire to the positive lead of the cap and a negative to the negative lead. Make sure you verify your work after you finish to make sure no leads are crossed and no polarities on the output dc side are inverted.

Step 4: Testing Time

Once its done and checked for accuracy, go test'er out! This is the stepper motor i'm going to use this circuit on. It's a 1.8* 2.8 volt 2 phase stepper motor. I put the phases in series so it is only a two wire a/c output instead of four wires. it also doubled the motor voltage output. Put the two motor wires onto the two a/c input wires of the circuit and then connect whatever you want to the circuit you want to use. I used a 12 volt led for now. There is more work needed to complete the wind generator but this is the essentials of it for testing purposes. Just spinning it with my hands (maybe 30 rpms worth?) The output was 12 volts more or less. Thats a long way from the original 5 volts on one phase. Since its a/c, the motor can be spun any direction or back and forth. it doesnt matter. The more load put on it the harder it is to turn so few rpm's in wind is better for more power. The caps smooth out the cogging stepper motors have also. Just getting twelve for the little turning I did on it made me happy so I am hopefully where I need to be on it. The simulator I used showed that I would get 24 volts DC from a 12 volt a/c input. With some good wind and a decent load I'm hoping ill be where I need to be.

I put a small video of me spinning it and powering the light. check it out.

Ill post more of this project as I go along but this instructable is for the voltage doubling circuit only. It can be used with other applications i'm sure. tell me any thoughts you have about it. thanks for looking!

Comments

[nico.botha.94]

hi, im also building a turbine, my magnet motor kicks out AC, i added a rectifier to the motor (not having to fix it anywhere else electronically), now i have DC comming out (obvious !! hihihi), my question is how do i double or tripple the DC Voltage (like you have done only with caps and mabey a switch or two) ?

thankls

[florlayamp]

Well the problem with my design is that I haven't done any thorough testing to see the limits of the circuit. Voltage wise it can handle up to 35 volts on the caps but I still have no idea on the current capacity of it. i'll probably blow it up testing it but that's all in good fun.

If you have time and some knowledge you can build on this circuit and even make it better, but if not, you can go the easy way and purchase an already complete and ready to go circuit and solder it up and be done with it like the ones here: http://www.ebay.com/bhp/dc-dc-step-up

[nico.botha.94]

ok sweet, thanks for the info !!

[domints]

If there were really AC voltage you should really pray that you are still alive, and probably healthy. Have you measured the voltage on output of the motor? This won't double the voltage, just straighten it (make DC from AC).

[florlayamp]

yes I measured the AC output of the motor. it's around 10 volts AC combined phases. it does give a good tingle when spun fast enoough.

[satya81]

Great...I had prepared exact replica of your boost circuit and checked the output on multimeter and it was awesome. I am using small ac stepper motor for wind turbine. Earlier output volt of turbine is around 1v to 1.5v. After connecting your boost circuit it is showing 4.5v to 5v. I am a Mech Engg and not well versed with Electrical stuff.Just followed your steps.When connected on load with LED the output remained at 3v to 3.5 v but my led is not at the brighter side as i wished. Give me some tips and have you done any modifications. I want to use this output to light up a 5LED light in my living room.

[florlayamp]

Awesome, im glad this circuit helped. I haven't had time to do anything else to it lately but its still on my list haha. for your little stepper motor, just keep in mind that the more load you put on it the harder it will be to turn so you might need some decent size blades for it. at 5v to work with, i would look into some cree led lights on ebay for flashlights to start off. if you can get up to 10 volts or more you have more options in the automotive area.

[florlayamp]

Congrats on building a successful replica of the circuit. To get more power out of it, lets start from the beginning. The stepper motor you're using might be too small to output a current big enough voltage to power your LED's without having to spin it really quick. The smaller it is the faster you will have to spin it to produce more volts. My decent sized stepper motor can power multiple car LED headlights very easy but my smaller ones can barely lite them up. The next thing would be the capacitors, the more uF's the better for stability and capacity. I can spin my motor one RPM and it would lite a typical 3 volt LED for 20 seconds or so. as far as making a wind generator, keep in mind that the more load you put on the motor it will also make it harder to turn. I've yet to mess with this circuit and the motor lately because im focusing on some solar projects at the moment. but its on my to do list. If you need a bigger stepper motor, scrap yards usually have pallets of them for dirt cheap.

[baecker03]

you could probably use smaller and more efficient diodes to rectify the AC.. which might give more output. I would use a boost DC to DC converter to possibly increase the voltage more. there are also integrated circuits that do a good job with this aspect and also monitoring the charging.

[florlayamp]

Great suggestion, ill have to try it