TheBackShed.com

Forum Index : Solar : Stand alone little Solar System

Author

Message

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 06:34pm 23 May 2012

Copy link to clipboard

Print this post

Wanted to make Subject: Stand alone little System (Solar battery + Fan)
but it didn't fit.

While I am still undecided to make my solar powered system with batteries and regulators,
I thought I will start with something without need for the batteries.

Thought about some air fan type cooling arrangement that will work when Sun shines.
No need to move air when Sun doesn�t shine.

Components that I can think off are:

Solar battery
Air fan

I can buy solar panel: 35W, 40W, 50W or 65W
All of them seem to have: Maximum Power Voltage - 18V, Open Circuit Voltage - 21.8V

I thought to buy 12V MagLev fans that are low on friction and are long life devices compared to ordinary fans.
There are some 24V MagLev fans as well
Not sure if it is better to run 12V fan on 18V battery or 24V fan would be safer.
If neither, I will need some kind of Voltage step-up or step-down converter.

Right now I have 240V Low Energy Fan that uses 5.5 W, but to use this one I would have to run some kind of inverter and definitely capacitor would be probably good to run in this arrangement as inverter needs some power just to run.

Either way to make this system more advanced , possibly some kind of capacitor that will accumulate power when not enough direct power to run air fan, with switch to turn fan on and off when capacitor exhausted.

And the question is how should I calculate what is needed and which components will best suit this little arrangement?

Another question would be what sort of cable to use if I have to have fan about 10 metres away from the fan?Edited by Georgen 2012-05-25

George

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 06:46pm 23 May 2012

Copy link to clipboard

Print this post

Most 24v fans will run OK at 12v, even less. At 18 volts in full sun it would be fine.

A 12v fan will die a early death if run at much over 15 volts, and be noisy to boot.
You could use a little 7812 regulator to keep the voltage safe for the 12v fan. Or run two matched 12v fans in series.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 08:09pm 23 May 2012

Copy link to clipboard

Print this post

I found this on 7812,

7812 input up to +35V output fixed +12V

Excuse my ignorance, but it has 3 pins
Explanation says: 1 Input, 2 Ground, 3 Output

So I understand it goes like this:
2 Ground - pin is connected to negative side of solar panel and negative inlet on fan
(if there is such a thing, as to my knowledge DC fan connected in reverse just changes direction of fan so instead of blowing is sucks or blows in other direction)

Positive wire from solar panel goes to 1 Input

And 3 Output is connected to other connector on fan.

12V MagLev fan looks to draw just 1W , well under 1A

But on closer inspection noticed that there are 3 types:
- Negative Voltage Regulator
- Positive Voltage Regulator
- Voltage Regulator

??? � bit beyond or should I say above my current knowledge

EDIT:
Looks that even 5W Solar panel will be enough for this type of fanEdited by Georgen 2012-05-25

George

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 08:39pm 23 May 2012

Copy link to clipboard

Print this post

Yeah you on the right track. A 7812 is a positive regulator, where common is negative. You also need to add a couple of capacitors on the input and output. A 10uF 63v cap on the input and a 1uF 16v cap on the output will do, its only approximate and not critical.

Most modern DC fans have built in electronics, and cant be connected the other way around, they either wont work or go "fitzzz" and smell bad.

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 12:13am 24 May 2012

Copy link to clipboard

Print this post

JayCar has 10uF 63V capacitors, no problem here, but they don�t seem to have

[quote]
1uF 16v cap on the output
[/quote]

Which way should I go for substitute?

I suspect that I should stick to 16V and go for 10uF, 100uF or whatever uF I can get ?

Would it be acceptable way to go, or I better stick to both values closely?

EDIT:
Noticed JayCar has 10uF 16V - would it do?

EDIT2:
On E-Bay I can have 100 off 1uF 16V capacitors for bit over $4.
If they burn quickly I'll have few spares

Edited by Georgen 2012-05-25

George

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 02:03am 24 May 2012

Copy link to clipboard

Print this post

Capacitance is important, voltage isn't, so long as its above the maximum. I picked 16 volts because it gives about 25% safety margin over our running voltage. A 1uF 25 volt, or 63volt, or even 1000volt would all be fine, so long as it's above 12v plus a bit.

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 03:46pm 24 May 2012

Copy link to clipboard

Print this post

Thanks, will stick to 16V then

Do I understand it correctly, that if I get 24V MagLev fan I do not have to install any of this?

Also, could you shed some light (101

) on why are those capacitors needed when I use 7812 regulator for 21V solar battery and 12V fan?

Could it also mean that just in case I can isntall 63V capacitor for 24V Fan?

(Is it that capacitor accumulates charge and helps to kick over the fan?)

George

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 04:06pm 24 May 2012

Copy link to clipboard

Print this post

No you wont need the 7812 if you use a 24v fan. But be aware the fan wont be running at its full speed, as its not running at its design voltage. I've used 24v fans in a few 12v projects and they work fine, but obviously not as fast as if they were running at 24v.

The capacitors are there to stop the 7812 oscillating, and keep its regulation stable. Dont worry about the why, its complicated, but they are necessary.

There's nothing to be gained by adding caps without the 7812. Well maybe there is a tiny tiny gain, but unmeasurable and not worth spending the cents on a cap for. If you have a cap lying around, cant hurt to add it, but dont put much effort into it.

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 05:33pm 24 May 2012

Copy link to clipboard

Print this post

Much appreciate your help.

Will probably go the 24V way, as it looks that it will be much harder for me to make something wrong.

I can get this 24V Fan:
Sunon 24V 80mm X 80mm X 25mm MagLev DC Fan
Power Current 0.22 AMP
Power Consumption 0.22 WATTS
Speed 4700 RPM
Bearing VAPO

Now question is which Solar Panel to get?

5W would be sort of OK when Sun shines well
But when rays fall at low angle, (winter, slight overcast, early morning, late afternoon) then 5W panel produces 1W or less and Fan stops.

10W (without bypass diodes) would make fan run longer,

35W will be better again (also this panel comes with bypass diodes, not important for my application now, but one never knows where panel will end up, as this is my first project and chances are things might snowball from here)

I understand that excess Wattage will not hurt anything, panel will just get little bit warmer and possibly deteriorate at faster rate.

EDIT:
And chances are that with little bit of extra knowledge, I will be able to make excess Wattage to do something else, all I will have to do is find the device that Panel will feed fan first and excess will be diverted somewhere else - (

suppose easy to say)Edited by Georgen 2012-05-26

George

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 01:37am 27 May 2012

Copy link to clipboard

Print this post

Is it possible to have larger Solar Panel (like 65W)
and use also surplus of what 24V fan doesn't need?

As I said, Fan is nuber one priority, but because it only needs 1 or 2W the rest will be available for something else
(If I only get help how to do it)

George

Gizmo

Admin Group

Joined: 05/06/2004
Location: Australia
Posts: 5078

Posted: 02:08am 27 May 2012

Copy link to clipboard

Print this post

Hi George

Yeah the panels dont get warm or anything like that, the watts is just a measure of what they can supply, but you can use much less.

As your in the learning stage, I would just buy a smaller panel for now, so you can experiment. A 35 watt panel can be used for a bunch of projects, charging a workshop battery, to power a workshop radio, some LED garden lights, a few fans, etc.

Glenn

The best time to plant a tree was twenty years ago, the second best time is right now.
JAQ

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 03:57pm 28 May 2012

Copy link to clipboard

Print this post

Hi Glenn,
One more question if you don't mind.

If I get 35W or 40W Solar Panel
If I get 24V MagLev Fan

If I also put + AND - wires into Solar Regulator Charger.

Is it reasonable to assume that Fan will get power first and regulator will use the rest?
Or regulator will rob most of the power and fan will not work with all power being used by regulator to charge the battery.

And to achieve what I have in mind I will need sophisticated electronics device?

George

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 02:26pm 13 Jun 2012

Copy link to clipboard

Print this post

Things changed a bit as I have 12V fan now.

What I noticed that fan seems to labour hard, driven straight from 12V battery and I don't think I need that much air.

I used 9V alkaline battery and fan worked strongly too
Thought how low can it go, so I used spare 3.6 cordless phone battery and fan moved almost enough air.

Making me think that 5V from USB outlet would probably be enough.

Thing is I have to work out which terminals on USB are for power.

Only question would be: am I likely to kill prematurely my little fan running it on 5V instead of 12V ?

Will have to gather more devices that change voltage from 12V battery to charge my 3.6V phones, 5V GPS as going from 12V DC to 240AC only to go back to 3.6DC or 5DC makes no sense.

George

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 06:56pm 13 Jun 2012

Copy link to clipboard

Print this post

Got a little 2A Voltage Step Down device with main component LM2596
[ LM2596 DC Converter Power Module Output 1.5-35V Step-Down Adjustable
Input voltage: 4.5-40V
Output voltage: 1.5-35V (Adjustable)
Output current: Rated current is 2A, maximum 3A (Additional heatsink is required) ]

Image copied from E-Bay

Because it has no reverse polarity protection and no protection if current above 2A
I was bit paralysed how to approach it.

Thought about using it for droppig voltage for my 12V fan.
It only draws 0.8W at 12V, so should be OK

Unscrewd until voltage dropped down to 5V with fan running

Kept fan going for 30 minutes and when I touched LM2596 module could not feel any heat, so getting rid of heat for 30 minutes was no problem.

Might be different story with ambient temperature 40 deg C on odd occasion when inside garage gets that hot during heatwave.

Am I up for any nasty surprise later on, or I should be OK?
Edited by Georgen 2012-06-15

George

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 07:46pm 13 Jun 2012

Copy link to clipboard

Print this post

Noticed on E-Bay this device:
5-35V LM2596 DC-DC Stepdown Adjust Power Supply Module f battery LED solar panel

It has 3 adjustments, 2 of them understand, one is V-volts second one is A-amps,
Cannot work out what is 3-rd adjustment for?

Picture copy from E-Bay

George

Georgen
Guru

Joined: 13/09/2011
Location: Australia
Posts: 462

Posted: 05:15pm 15 Jun 2012

Copy link to clipboard

Print this post

If I understand it right, I could be able to charge my 3.6V batteries
setting output to say 3.7V and limit curerent to 50mA or 100mA (will have to check out)

Also I could charge GPS, setting another one of those to 5V and correct current

For USB charge I noticed device on E-Bay specifically for USB application
pre-set to 800mA

Picture copied form E-Bay

Is it correct assumption?Edited by Georgen 2012-06-17

George

Print this page

To reply to this topic, you need to log in.