I am looking for a mini generator

metron9

The Lighthouse that uses my solar led array is in need of additional power when the sun is not shining. I came across this site that says the little motors here can produce 1000mA at 12V. All I need is another 40 or so mA. Has anyone here got any experience with the best type of motor to use for this. Are there manufactures that sell tiny generators that might fit this.

I have just started googeling the subject but I know someone here has some experience with this.

http://gizmodo.com/gadgets/gadgets/grad-student-creates-micro-windmill-155875.php

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

Bruce Bates

metron9 -

Is there a battery in your present configuration? If not, a small rechargable battery (or small bank of same) might well get you over the hump. Smaller time periods can often be handled by super-capacitors. Remember, it's not just the amperage you have to worry about, but the time period as well. In other words, I suspect you need additional amp-hours, not just additional amps.

If you opt for a mini-generator as you were proposing, what had you planned to power it - water power, wind power, something else?

Regards,

Bruce Bates

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metron9

The system uses a 4V SLA battery and will run with no charge for about 60 hours at 27mA. It uses the small solar panel from spark fun to recharge. All is fine during the summer and i cut off the system at 3.8V and warn of a low battery if there is no sun for a week. I am thinking a small garden spinner with a tiny stepper or DC motor could pick up the slack during bad weather, especially when winter solar is so low. Adding solar panels in the winter won't help much if there is no sun. The customer does not want to plug in. I suggested a battery pack that could be removed and charged indoors as another option. They just want more light than they have solar power so it is running at the edge of its power capacity.

I tested some of the $2.50 cent steppers from futurlec, (I had bought them from another company for 4x the price a few months back hehe..) those things can give you 100mA at over 12V just spinning back and forth with your fingers. So something like that could work. I suggested he adds a windmill to his lighthouse products. The lighthouses go for $700.00 each for the nicer ones and he has sold many more this year because of my simulated rotating light that has much more light than the menards solar light (single yellow led) that ran from a single 1.2 rechargable battery.

Really I am wondering is specific generators in this size range are made or if just using a stepper is ok to do as well as what seems to be the best type of motor to use, I guess at least 3 phase is better than 1 or 2 and the 5 phase little steppers like i said can generate quite a bit of power.

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

Bruce Bates

metron9 -

Personally, I'd stick with the idea of a DC PM motor, primarily due to price and availablity. Additionally, they would be much easier to wire up than a multi-pole stepper motor.

At this juncture my thoughts are running towards a wind turbine sitting atop the "roof" of the lighthouse. I'm speaking of the rounded vane-type wind turbines which are used to exhaust smaller flues, sheds, and other areas, just to create some general air circulation or exhaust.

I'd try running a shaft down from the top onto a gear. The gear, in turn, would engage with a second gear on the motor to provide some mechanical advantage which may be necessary with this system. I just don't know if "miniature" vane turbines are made, and/or if the smallest regular vane turbine would be too large for the lighthouse.

This is the type of thing I was considering:
http://www.grainger.com/Grainger/categories/hvacr/exhaust-fans/wind-driven-turbine-ventilators

Regards,

Bruce Bates

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Bean

Metron,
Wind power is even more unreliable than solar. I think you would be better off with a "charge pump" type solar charge circuit that can charge the batteries even on cloudy days. And more battery capacity. And try to make the light more efficient. Also does anyone REALLY care if the light is not on 1% of the time ?

I also think a "windmill" would detract from the look of the lighthouse, just my personal opinion.

Bean

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www.hittconsulting.com
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metron9

Hi Bean. The windmill would just be a remote location it is not possible to design it into the lighthouse. The windmill or spinning device would just be in addition to the solar panels especially in the fall and winter months, course depends on ones location if they have enough wind. I just don't think it would have to be very big to get 40mA at 4V. I am thinking more along the lines of the little spinning devices one typically sees in plurality in the embodyment of some gardens. (oops reading to many patents) I will be doing some experiments.

Actually the solar panel I am using with the 4V battery charges very well at low light levels, I have played around with solar charge circuits and with this particular combination it would not be worth the trouble but I will do some more testing on cloudy days. Using 2 panels would help and that is what he is going to do now. I am also going to put in some timer logic to reduce the overnight on time when the battery starts out with a lower charge. Perhaps letting it run for 5 nights in a row when no sun rain days keep it from charging is a little much to expect as well.

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

ChrisP

Its a little pricey perhaps, but there are plenty of very small 3 phase brushless RC aircraft and car motors, it would be simple to rectify with a 3 phase bridge, and no brushes to wear out... Should fit in the package size your thinking of an supply way more current than you need, so you would still make your minimum at very low wind conditions...
http://www.radicalrc.com/shop/?shop=1&cat=182&cart=735597
$25 new

metron9

Hmm you know when you are into too many things when you just happen to have one of those in a bin.

I have one that runs at about 20amps using an E-Flight ESC.

I just tested it but at a few hundred rpm I can only get about 1 volt out of it using 6 schottky diodes. Perhaps you have to be in the thousands oof rpm to get the voltage higher.

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Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

kelvin james

I don't know if this will help you or not, but since i have not seen this idea brought forward yet, i figured now was a good time to do so. Someone gave me a hand crank powered flashlight, it has 3 leds' and holds a charge for a very long time. It has a geared mechanism from the crank to drive a generator type flywheel and coil to charge what i presume are batteries in it ( i have not dissected the innards yet to get the full story ). Anyway, this thing is dirt cheap, charges up with a few cranks, and like i said holds a charge for a quite a bit. I think driving the mechanism from a wind source would be a good way to always have an available power source. Being a geared flywheel, it does not take much to get it moving ( so little prolonged wind strength needed ) and being a flywheel means it keeps rotating on its own for a short period of time afterward. This a ready made and cheap generator. I realize there are technical issues to be looked into regarding its use. I don't know why people have not adopted this as an extra power supply for robots ( to power sensors ? ), it could be driven from the drive train ( axle ), acting much the same as an alternator in a car.

Dennis Ferron

A tiny motor producing 1000 mA at 12 volts? That doesn't sound right. That would be 120 Watts. That's more power than a powerwheels car uses out of two large motors when it pushes a 75 lbs kid around at 11 MPH. You probably couldn't pump 120 watts into a small motor even if you spun it fast enough to make the armature fly apart, and even if you could put 120 watts of mechanical energy into it, the coils would burn out from the electrical energy coming off it. You'd probably need a motor at least as big as a soda can to generate 120 watts, and it would take a great deal of force to spin it - a person riding an excercise bike vigorously generates only 100 watts.

Edit: Nevermind; I misread 1000 mA as 10000 mA. Big difference.

Dave Hein

Can you use a more efficient light source instead of adding more charging capability?· If you are currently using an incadescent light source you could improve the efficients by·changing to·LEDs or flourescent lights.· This would let the charge last longer during the night by using less power.

stephenwagner

Razor 80Watt - 100Watt - 200Watt - 250Watt·24V Scooter Motors work great.

Google/Yahoo Scotter Part & Scotterparts.

SJW

metron9

Hi Dave. The unit actually uses 18 LED's and a mega48 with PWM to sequentially drive 2 led's in the circle. One·from 0% to 100% while the previous one goes from 100% to 0% to simulate a rotating light. The two red LED's in the center create a backdrop to the white light so it improves the illusion that the unit is rotating. The outside panels of the lighthouse are textured plexy glass that refracts the light so you don't see the LED directly.· So the unit at 4.1V actually uses about 27mA while running when the voltage drops to under 4V it is using only about 20mA. Once it shuts down it monitors the battery voltage as it wakes up from sleep every few seconds and only uses .25mA. When the battery falls below a set point it blinks the red lights for a millisecond every 3 seconds to warn the user of a low battery.

So far with a year of use and about 100 lighthouses in the field we have no complaints excecpt for one where the fuse holder was not connected correctly and the battery never charged. I just know the unit is at its limit in on time and brightness with the available solar recharging and I think if it can be done that wind power in combination with the solar would be better than just adding solar capacity and give the customer another product to sell.




▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Think Inside the box first and if that doesn't work..
Re-arrange what's inside the box then...
Think outside the BOX!

skylight

metron9 said...
Hmm you know when you are into too many things when you just happen to have one of those in a bin.

I have one that runs at about 20amps using an E-Flight ESC.

I just tested it but at a few hundred rpm I can only get about 1 volt out of it using 6 schottky diodes. Perhaps you have to be in the thousands oof rpm to get the voltage higher.

You could try using a·low voltage·DC current through one of the windings to excite and gain more voltage?

or as the beach boys would sing you need a little bit of "excitation"

Post Edited (skylight) : 11/5/2007 7:35:06 PM GMT