voltage regulator

[bob01]

Hi - new member and total amateur here looking for a little help. Thanks for any help in advance.

I have a little project to build a solar powered heat ventilation fan for my garage. I have a 12 volt fan that draws 2.5 amps so I bought a 12v 30 watt panel. I understand that the panel will actually generate more than 12 volts (just measured it at 20 volts using my multimeter) so I thought I would be smart and put in a 12v voltage regulator to step down the voltage to the fan.

What I ended up with was a little device that functions as a combination solar charge controller and voltage regulator. I assumed I could connect the panel to the panel inputs and the fan to the "Load" outputs (no battery connected) and I would get a nice 12v output. In reality I'm not getting anything through "Load" so now I'm thinking that this little device is wired to generate the "Load" output from a connected battery and not as a stepped down voltage from the panel directly.

Can anyone confirm this? If so, what is the standard/common way that folks use to ensure they are only getting 12v from a panel?

Thanks again,
Bob

[sensij]

Can anyone confirm this? If so, what is the standard/common way that folks use to ensure they are only getting 12v from a panel?

Yes, without a battery attached, your solar charge controller will not have a source of power to turn on... it won't use the panel power until it knows how to regulate it. So, the short answer to your question is to hook up a battery to the charge controller, and get the "regulated" 12 V from it.

You should know that your 30 W panel will almost never put out 30 W, and the charge controller is probably PWM and will only be passing some percentage of whatever the panel produces. If you really want to run a 30 W device for several hours a day, you will need a lot more panel than what you bought.

There are some fans that will accept power in a wide range up to the 20 V or so that the panel you bought might put out. Those fans can run directly off of the panel, no regulator required, although you might expect the speed to vary depending on how much sun you are getting.

[bcroe]

I have a little project to build a solar powered heat ventilation fan for my garage. I have a 12 volt fan that draws 2.5 amps so I bought a 12v 30 watt panel. I understand that the panel will actually generate more than 12 volts (just measured it at 20 volts using my multimeter) so I thought I would be smart and put in a 12v voltage regulator to step down the voltage to the fan. Bob

I would suggest, that many "12V" devices, esp motors, have a pretty wide voltage capability. Yours likely
would be happy to 15V, as found in most charging systems. AND your panel may not be able to get above
15V with the motor attached. I would test it before making more revisions. Bruce Roe

[Sunking]

a 12 volt 30 watt battery panel is too small to run the fan. You will never get 12 volts out of the panel. The issue is a solar panel is a CURRENT SOURCE, not a VOLTAGE SOURCE.

A 30 watt battery panel has an Imp of roughly 1.7 amps, and the fan uses 2.5 amps. That means for a few moments around solar noon all you will see is 7 to 8 volts out of the panel and a fan turning at 1/4 of rated RPM if it even runs at all. The other 23 hours of the day will not run as there will not be enough current.

[bob01]

Great info. Thanks everyone. Much to learn!

[bcroe]

If you really want it to wok, you could use 3 of those 12V 30W panels in parallel. You might see some
excess voltage on a good solar noon, so then tilt one somewhat to the east and one west, till the voltage
drops. This will extend the hours that the fan is effective.

Buying very many of those tiny panels might get expensive pretty fast. I would take a single much more
economical (per watt) 250W (grid tie) panel, 60 cells gives 30 to 37V. Put one of those $2 buck converters
on it set to 12V out for your fan. On sunrise, the converter will just pass current directly through, till there
is enough current for the motor to get going. Once you hit 12V, it will start regulating, for quite a long day.
Not quite as good as an MPPT on day extremes. Bruce Roe

[bob01]

Put one of those $2 buck converters on it set to 12V out for your fan.

The fan has 3 settings (lo, med, hi). The high setting draws 2.5 amps but the low setting I think is less than 1 amp; I'll have to go look it up. I'm going to wire it up here in a couple of days and just see what I get on low. This is more about a learning project and less about actually trying to solve my garage heat problem (although I wouldn't mind if it actually worked). I may look at other options going forward with other panels, so thanks for the advice.

I am curious about that $2 converter. That was my original question; how to regulate the voltage around 12 volts. Turns out I may not need it right now but am still wondering how that works. What converter exactly? Does it have a name that I could search for, or do you have a link? Thanks as always. This forum has been very helpful!

[Sunking]

The fan has 3 settings (lo, med, hi). The high setting draws 2.5 amps but the low setting I think is less than 1 amp;

OK that give you around 1 maybe 2 hours a day run time around solar noon.

[bcroe]

I am curious about that $2 converter. That was my original question; how to regulate the voltage around 12 volts. Turns out I may not need it right now but am still wondering how that works. What converter exactly? Does it have a name that I could search for, or do you have a link? Thanks as always. This forum has been very helpful!

Just search DC-DC buck converter; plenty of cheap ones on E+ay. Basically it takes higher voltage at lower current
in, gives lower voltage at higher current out, at quite high efficiency. If the power is there it will regulate to an
output voltage you set; if not it will go to straight thru short. Bruce Roe

[bob01]

Thanks to all

Just wanted to circle back around to say thanks for all of the help. I was able to put together a voltage regulator circuit and everything works great. Surprisingly, given the feedback, I am happy with how well and for how long the fan runs. The sun hits the panel starting around 9:30 am and the fan fires right up and runs at a consistent medium speed until shade hits the panel again around 4 pm. So all on all, a fun and successful project!

Thanks again,
Bob

[bcroe]

I was able to put together a voltage regulator circuit and everything works great. Surprisingly, given the feedback, I am happy with how well and for how long the fan runs. The sun hits the panel starting around 9:30 am and the fan fires right up and runs at a consistent medium speed until shade hits the panel again around 4 pm. So all on all, a fun and successful project! Thanks again, Bob

Excellent results, thanks for the report. Bruce Roe

[posplayr]

DC-DC XL6009 Step Up Power Apply Module 3V-32V to 5V-35V Replace LM2577

http://www.ebay.com/itm/171301504949?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It uses the XL6009 device with a cookbook circuit from the data sheet. It probably doesn't have reverse voltage protection and it is a bare board but for a hobby board it fits the bill very well.

Model Specification:
1. XTW6009 boost module
2. Module Properties:Non-isolated boost (BOOST)
3. Rectification:Non-Synchronous Rectification
4. Input Range:3V~32V
5. Output Range:5V~35V
6. Input Current:4A (max), no-load 18mA (5V input, 8V output, no-load is less than 18mA. Higher the voltage, the greater the load current.)
7. Conversion efficiency:<94% (greater the pressure, the lower the efficiency)
8. Switching frequency:400KHz
9. Output Ripple:50mV (the higher the voltage, the greater the current, the greater the ripple)
10. Load Regulation:±0.5%
11. Voltage Regulation:±0.5%
12. Dimensions:43mm*21mm*14mm (L*W*H)

[bcroe]

DC-DC XL6009 Step Up Power Apply Module 3V-32V to 5V-35V Replace LM2577

http://www.ebay.com/itm/171301504949?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It uses the XL6009 device with a cookbook circuit from the data sheet. It probably doesn't have
reverse voltage protection and it is a bare board but for a hobby board it fits the bill very well.

It also has a minimum of input and output filtering, and shielding. Without those at 400 KHZ its
a good radio interference generator. But those are easily added. One of those switchers was the
first thing I worked on at my job. Now just an off-the-shelf item, cheap.

Generally solar is arranged to do buck (reduction) voltage control. Buck-boost is getting to be a
common function, but some efficiency & simplicity is lost. Bruce Roe

[posplayr]

It also has a minimum of input and output filtering, and shielding. Without those at 400 KHZ its
a good radio interference generator. But those are easily added. One of those switchers was the
first thing I worked on at my job. Now just an off-the-shelf item, cheap.

Generally solar is arranged to do buck (reduction) voltage control. Buck-boost is getting to be a
common function, but some efficiency & simplicity is lost. Bruce Roe

Yes if you want to reduce EMI a metal enclosure with shielded properly grounded cables is required. EMI will not effect that motor, the brushes probably create even more EMI than the converter.

I have been scouring ebay for various electronic items. The Chinese seem to be very good at coming up with inexpensive solutions to various electronics products. Where else are you going to get a $2, 4 amp dc:dc converter with free shipping?