wind powered night lights

[Graham]

Can anyone help me out with some advice? I'm wanting to expand on the idea of my solar panel christmas lights that I just packed away for another year, and put something a little more permanent/powerful in place. What I have in mind is a small wind powered generator to trickle charge a car batterry, which can then drive a series of small LED lamps installed up the driveway to light the way at night. I have found plenty of solar-based projects, but these tend to be either large scale (and therefore employing a relatively expensive panel) or small scale low voltage (which I could buy from my local hardware shop fairly cheaply, but wouldn't be useful because the driveway is shaded and nearest sunlit area is some distance away). The other aim for my project is "cheap" - making use of as much recycled, reclaimed, or readily available components as possible.

I can build myself a wind powered generator and the lamps themselves - I can even string the two together, but that means the wind has to blow for my driveway to be lit - hence the battery and charging need. It is really the circuitry (charging/switching) and design concerns in that area that I need advice on...

Cheers,
Graham.

 

[Resqueline]

If the generator is not too powerful it might not need any charging regulator at all.
Also be aware that a starting battery is not as suited as a storage battery is.
What type of generator do you have in mind?

 

[Graham]

Hmm - I wasn't aware that there was a different 'type' of battery - I'd always assumed that those banks of batteries you see connected together as UPS backups were just basically car batteries... however - as I said, my project is about recycling, using what I have available, and buying as little as possible (the LEDs are going to be a relatively major expense on their own). So with those criteria as my starting point, and given that I have an old car battery available - would it be 'adequate' even if not ideally suited?

My intention for the generator is again based on 'thrift', and grabbing a DC motor out of some appliance that I find at the side of the road (I've seen various articles on the net using motors from old video recorders or from printers - I have a couple of motors already I can try - one is a stepper motor from a trashed flatbed scanner, and the other was from a decorative xmas light that spun a coloured disk under some optical fibres - the latter spins quite slowly probably in the region of 100 RPM).

I'm talking small scale and low voltage/low current output - though I haven't mocked anything up yet to get sample figures. Is there anything specific I need to aim for - presumably a voltage output around 12v dc (or AC with a bridge?) is required to charge the battery in the first place...

I wasn't anticipating putting any kind of governor or brake on the generator, though I read somewhere that if you have a load across the output, that acts as a brake anyway...

Cheers
Graham

 

[Resqueline]

Well, maybe there isn't too much of a difference after all. I just read somewhere that the only type that stands out are the very expensive traction batteries. Making use of what you have at hand is perfectly ok, & adequate I'd say. Just don't discharge it too deep (50%) and it'll be ok.

Using permanent magnet DC motors should be ok, disk-drive & steppers also. Many of them will need considerable rpm's to get up to 12V though. If you apply 12V to them and measure their off-load speed (& add some %) you get the minimum rpm they need to spin with to begin charging. Getting them up to this speed will be your challenge. Thus 24V motors will be better suited than 12V ones, and lower voltages are less suitable.
Brushed motors needs just one diode in series. Steppers & other electronic commutated motors will need full bridge rectifiers (2 or 3 phase) connected to their windings. The low-speed motor you mention is a geared synchronous motor. It may need a big prop to spin but it might work.
You can fab a number of generators and hook them in parallell. Each will contribute with a more or less constant current. Unless there's hurricanes in your area I don't anticipate that such small generators will need any particular protection.

 

[Graham]

Disaster strikes...

Many thanks Resqueline. Thanks for the insight on the battery - thats good to hear.

Nice lateral thinking with the voltage from the motors - a 24v motor is presumably going to be easier to spin up enough to deliver just half its rated voltage, than a 12v motor will be to deliver its full rated voltage - why didn't I think of that!?

Sadly - my project, and in fact ANY electrical work, has suddenly taken a nose dive - one of the leads on my trusty little multimeter that I've had for about 30 years has broken - a visit to Jaycar for a replacement (lead or plug) has proven fruitless. The meter (an ICE Microtest 80) has pretty small sockets, and being from Italy and 30 years old probably doesn't help, so it looks like a new multimeter will have to be my first purchase - damn! I guess it is about time I went digital, but I will miss my little baby...

 

[Resqueline]

Sorry to hear that. I see it has a very nice & big dial. One could say that it's about time a lead broke for you, it usually takes about a tenth of that time for most people to experience that. You are obviously taking very good care of your stuff - but maybe it's time for the museum for that one. Are you sure it can't be soldered &/or glued back together, or mended with some 2mm brass wire/stock? 2mm plugs are still on the market afaik, even if they're not used in instruments anymore (except for the probe part).

 

[Graham]

If I can fix it, I will. This old dinosaur likes the meter rather than digital display, even if it isn't quite so accurate. It's not ready for the museum just yet! ;-)

 

[Graham]

ok - picking up the project again after a pause for real life drudgery...

I've salvaged a pcb from a garden solar light, and while all the voltages and values will be wrong, I figured that the principles of its operation would at least help me design something to switch my lights on when it gets dark. But for the life of me, I can't figure out how the thing works. The basics of it appear to use 2 transistors, one of which is triggered by a base-emitter voltage from the solar panel, and the second is triggered by the first - so the way I see it, the whole thing will only work when there is voltage from the solar panel - i.e. during daylight!? I guess I'm missing something fundamental - I'll keep studying the circuit...

Components
D1 = 1N5817
D2 = White LED
Tn = S9013
C1 = 1000pF ceramic
R1 = 100K
R2 = 10K
R3 = 150 (fat)
R4 = 47 (fat)
R5 = 240

Hmm - maybe I just had an epiphany...? If the solar panel creates electricity and therefore turns on T2, which then turns on T1, then maybe that provides an easier route for the electricity than the LED does, and terefore the LED is off. When the Solar panel does not produce electricity, this holds both transistors off, and therefore the only route is through the LED? However - if all this is correct, then how does the solar panel ever charge the battery, if it's power is being dumped through T1?

Any thoughts - or understanding from anyone would be gratefully received.

Cheers
G

 

[Graham]

Epiphany revised...

OK - I think I now understand the operation of the circuit...
There are three states
1. The battery is discharged and the solar panel is providing power.
2. The battery is fully charged and the solar panel is still providing power
3. The solar panel is not providing power, and the battery is operating the LED

And this is my theory...
In state 1, the discharged battery holds the voltage from the solar panel below the battery's capacity (1.2v) while it is charging.
Once the battery is charged to capacity (state 2), the voltage from the solar panel rises above 1.2v, and once it hits 1.4v (Vbe of the S9013 transistors), T2 switches on, allowing the power from the solar panel to be dumped out through R3 and T1 (now also switched on) as the resistance across the emitter and collector of T1 is less than the resistance of the LED (presumably - otherwise, I guess the LED would light up). This prevents over charging of the battery.
Finally (state 3), the sun goes down, and the solar panel provides no power (my tests showed that it had to be quite dark for the panel to provide less than the 1.4v switching threshold). Now T2 switches off, effectively switching off T1 as well, so the only available path for power from the battery, is via R3 and the LED - Let there be light!

The only thing I'm not clear about (assuming my description above is somewhere close to the mark), is why the need for the second transistor, and what function does the capacitor serve? Ah - re-reading my state 2 description, I think I see the need for the second transistor - is it to provide an easiest path for the electricity, by-passing the LED?

Someone help me out here? I feel like I am almost there, but would appreciate if someone can tell me I'm going the right way...

Cheers
G

 

[Resqueline]

The clue to the solution lies in that R3 & R4 are not resistors, but inductors. (> R3=L1, R4=L2)
1.2V is not enough to make any LED light (except an IR one) so there's a need for a boost converter.
T1, L1, L2 & C1 are making a flyback inverter. C1 charges, turning on T1, drawing current through L1, C1 discharges, T1 turns off, L1 "flies back" up to a voltage high enough to light the LED, cycle repeats. Frequency determined by L2 & C1.
Then comes the sun and turns on T2 which kills any base current to T1, effectively shutting off the inverter & the LED.

 

[Graham]

Many thanks Resqueline. I must confess I was wondering how a single battery would run the LED! So, a 'flyback invertor'...? Thanks for the description of how it works - I'll need to do a little research on what makes a resistor into an inductor

Cheers
G

 

[Eufouria]

Hi guys!

When I saw the title of this thread I had to do a double take, this is the exact project I'm working on right now and came here to look for help on.

If you don't mind I'll give a brief rundown of my ideas:

I've got an old fan motor which I'm using, 12v

I plan on using the battery from a UPS, I saw you guys were discussing this earlier and I would suggest you look for a deep-cycle battery as well.

I'm going to use a AC inverter designed for a cars lighter socket.

I plan on powering a LED constellation for my ceiling which shouldn't require more than 6 LED's and some fiber optics.

Issues:
I don't think I will need a charge controller as the fan motor produces very low voltages.

When I hooked up my voltmeter to the motor and hand-spun it it gave me readouts of .6 volts then -.6 then .6 back and forth. Which leads me to believe it is a stepper motor which I don't have much experience with.

I also am not considering a dump load as the voltage is so small relative to a UPS input.

Lastly I am worried about the low voltage I am getting and hope that this small trickle of energy will build up in the UPS am I wrong to assume that? Will the UPS require a certain level of power to begin storing more?

I apologize if any of my questions are novice electronics are a hobby and all the information I have collected has been simple internet research.

Look forward to seeing how your project progresses Graham!

 

[Resqueline]

Old fan motors are rarely steppers (I've only seen one such application in my lifetime) but computer fan types have long since been electronically commutated (internally) and are actually 2-phase 90-degree steppers.
Almost any motor can be made into a generator, you just have to find out how, and how fast it'll need to be spun.
I'd stay away from using DC/AC inverters to run a few LED's though, that wastes a lot of energy.

 

[(*steve*)]

Hi guys!

When I saw the title of this thread I had to do a double take, this is the exact project I'm working on right now and came here to look for help on.

I was going to post this link last night, but I noticed the thread had drifted to the topic of LED garden lighting.

Stepper motor wind generators

I've been interested in doing something with these too.

This page has some good ideas for making cheap turbine blades too.

If you don't mind I'll give a brief rundown of my ideas:

I've got an old fan motor which I'm using, 12v

I plan on using the battery from a UPS, I saw you guys were discussing this earlier and I would suggest you look for a deep-cycle battery as well.

I note the suggestion that a higher voltage motor will result in a usable voltage at lower RPM (i.e. less wind)

I'm going to use a AC inverter designed for a cars lighter socket.

Do you want mains voltage? You'll probably need a lot of wind to be able to generate significant power.

I plan on powering a LED constellation for my ceiling which shouldn't require more than 6 LED's and some fiber optics.

Can you operate them from 12V? Converting to 240 (220, 110, etc) and then back to whatever they use (especially if it's 12V) is quite inefficient.

Issues:
I don't think I will need a charge controller as the fan motor produces very low voltages.

A simple overvoltage detection would work fine, but yeah, at low power it may not even be required.

When I hooked up my voltmeter to the motor and hand-spun it it gave me readouts of .6 volts then -.6 then .6 back and forth. Which leads me to believe it is a stepper motor which I don't have much experience with.

See that link I gave. Full wave rectification may be the most efficient way of getting power -- The question is whether the voltage is ever high enough to charge the battery.

I also am not considering a dump load as the voltage is so small relative to a UPS input.

If you need to be concerned about a dump load, then you're possibly also going to have to concern yourself with gyroscopic effects caused by changes in wind direction and methods of automatically feathering your turbine to prevent excessive RPM.

Yeah, not an issue with a little one

Lastly I am worried about the low voltage I am getting and hope that this small trickle of energy will build up in the UPS am I wrong to assume that? Will the UPS require a certain level of power to begin storing more?

In general, you'll need a higher voltage than the battery itself. The first link I gave (I think) suggests 24V or higher stepper motors as they will give usable voltage at lower RPM.

I apologize if any of my questions are novice electronics are a hobby and all the information I have collected has been simple internet research.

Research is rarely a bad thing

 

[Eufouria]

Thanks guys!

Sorry to hijack the thread Graham, let me know if I should start a new one.

So in order to charge the battery it will require a greater voltage than it outputs?
That doesn't seem right, I would think I should be able to trickle low voltage into it then use it at a high voltage for a short period.
The mention of computer fans got me thinking, I have a suitcase full of 92 millimeter fans that I could fashion into a sheet. The first thing I can't figure out it how I would daisy chain them. Since if one is turning and outputting power into the next it might be powering the fan as opposed to simply passing the power through. Would a circuit board with individual connections with diodes to each fan be able to channel their collective energy?

 

[Resqueline]

Steve's right. You're just confusing voltage and current.
Fan blades are not very efficient when used as generator blades due to their curvature becoming counteractive. Also, you'll have to get at the PCB inside to (disconnect the commutating electronics and) connect a rectifier. Apart from that there's no problem in connecting them in series &/or parallell as required.

 

[Graham]

Sorry to hijack the thread Graham, let me know if I should start a new one.

Hi Eufouria - sounds like our projects have a number of parallels - so I'm happy to keep the two together in one thread - as long as our mods are OK with it.

Steve - sorry for the drift 'off-topic'. I was hoping that by understanding this circuit, it would help me to build something that would switch the lights on when the light level dropped - judging by Resqueline's description of the induction loopback part of the circuit, it looks like I still have some more research to do around using the solar panel as the trigger to switch the lights on and off, but strip out the loopback part so that the lights are driven only from the 12v battery.

Thanks all for your input so far.

Euforia - I like the idea of building a mini-windfarm composed of many smaller units all built into a panel. If you wire them up in parallel, I think you get the smaller voltage but higher current, whereas if you wire them in series, you get higher voltage and lower current. Best of luck with your project too.

Graham

 

[(*steve*)]

Steve - sorry for the drift 'off-topic'.

Hahaha, don't apologise -- it was your thread

I had recently browsed something that matched the thread title, but didn't bother posting it because it seemed that you'd moved on.

If you're using a solar panel to charge a battery, you could use the panel to turn the lights on and off but it maybe just as easy to use an LDR. Those garden lights tend to switch on slowly which may cause problems with dissipation while they're turning on.

Using a schmitt trigger (like this http://webpages.ursinus.edu/lriley/ref/circuits/node4.html ) is a way to stop that. If you charge the battery via a diode, and then use the panel voltage (via a divider perhaps) as input to a schmitt trigger. It will change state when the voltage drops below some point and will not change back until the light level gets quite a bit higher. The output of the schmitt trigger could drive a larger transistor (possibly a mosfet) which switches the load.

I'm not so sure about many small generators in series or parallel. In theory it would work, but you'd expend an awful lot more effort making small generators than you would on making one slightly larger one.

Another option would be to take the AC and use a transformer to step up the voltage. This would increase losses, but for experimental (or very low power) use it should be fine.

 

[Graham]

Hi Steve,
Sorry - the solar panel garden lights is becoming a distraction from my original concept. My intention was only to understand the garden light circuit, so that I could possibly use the solar panel (and portions of that circuit) to control the switching on and off of my lights. I am still hoping to build a wind powered contraption to provide the charge to the battery during the day (and hopefully at night as well...) So the overall picture will be something like...
wind turbine creating power whenever the wind blows
if battery voltage below nominal, then turbine charges battery, else power is 'dumped'
solar panel detects daylight/night
when no voltage from the solar panel, then battery drives LEDs
when voltage from solar panel, then battery is isolated from LEDs

Sounds straightforward, but I'm still learning...

Cheers
G

 

[Resqueline]

Isolating the different energy sources when they're not producing is easiest done with just a diode in series with them.
You see the diode in the garden light? It's there to isolate the light detector/switch from the battery. If it wasn't there then battery voltage/current would go back to the panel and prevent the detector from working properly.
With wind generators above 2A on a 100Ah battery you'll likely need a shunt regulator. They're not very complicated.