How to light a bulb?

Makeitrein
Makeitrein Registered Users Posts: 5
Howdy everyone!

Right now - I am a tad overwhelmed with the details and intricacies of photovoltaic power.

So I thought I would start off small - lighting a fluorescent bulb with a solar panel.

No battery, no control panel - all I want is to see a nice bright glow.

As I understand it, the steps I need to take for this project this are:

1. Connect solar panel to inverter with soldering gun and flux.

2. Connect inverter to bulb with adapter.

3. Put in sun...

4. Profit?

Unfortunately, I am still a little shady (;)) on the details. A few questions that I have are:

1. Do I even need an inverter for a light bulb? Or, more broadly, what and what doesn't need an inverter?

2. How exactly do I connect the solar panel to the inverter? Likewise, connecting the inverter to the bulb with an adapter is a mystery to me.

3. Are there any solar kits that could teach me these lessons without wasting your guys' times?

High five to anyone who helps,

Jordan

(I have a gut feeling that there is a post on this forum answering all of these questions. Google said no - but if anyone knows a helpful thread - feel free to link.)

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: How to light a bulb?

    most inverters require a battery to work and the ones that don't are grid tied. also there won't be any regulation of the voltages the pv puts out and could damage or burn out the light if it were directly connected to a dc light and inverters too have their limits on incoming voltage. what you proposed if it were made to work somehow, would only come on when the sun shines and bulb intensity may waiver some with solar intensities too.
    can i ask what the purpose of this is for, for if it is for a demonstration then i'd go with a few solar cells and use that to light a flashlight type bulb?
  • Makeitrein
    Makeitrein Registered Users Posts: 5
    Re: How to light a bulb?

    Thanks for replying Niel.

    I did not know that inverters required a battery.

    This project was intended to be a testing ground for my next project - a solar powered ipod. I (mistakenly) assumed that I did not have to use a battery because the ipod already one inside of it.

    I realize now that I need more of a guided approach to learning about solar.

    Do you have recommendations for instructional kits/guides/videos/threads for a solar newbie? :cool:

    I'm wanting to get into the wide world of solar - but I'm paralyzed by indecision.

    Cheers
  • vcallaway
    vcallaway Solar Expert Posts: 157 ✭✭✭✭✭
    Re: How to light a bulb?

    You would have better luck using a small solar panel sold as a battery charger. Costco sells the Sunforce brand that works pretty good.

    The difference is they have a built in regulator. I've used one to charge my cell phone a few times. You are not going to power a bulb with one. Most are 5w panels. There are some 12v CF bulbs in that range.

    For something that small you don't want to covert to 120v then convert back to 12v. The loss in conversion is greater than you are producing.

    A 5w battery charger panel should power your ipod.
  • GreenPowerManiac
    GreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    Re: How to light a bulb?

    A great time to experiment ! With D/C. Grab some automotive bulbs and fixture them inline, maybe 5 tail light bulbs. If you're crafty with LED's, do that extremely efficiently. As the panel produces more power, the bulbs become brighter. There's nothing more inefficient than using an inverter for small power sources, so keep it on the shelf until you're comfortable with your small setup.

    Switch to using the inverter (A/C inversion from a D/C battery) only when you're running or planning to run higher wattages than say 100 watt minimum, otherwise you're wasting $$ & time.

    Watch out for the fluorescent bulbs as they consume more voltage to start (warm up) than the regular bulbs. The same for those swirly high efficiency bulbs you can buy at Wal-Mart for .92 cents each.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How to light a bulb?

    Solar Panels are just variable output batteries. And not many loads are designed to operate correctly when connected to a source that has voltage and current that varies over time.

    You can look at a solar panel's I*V curve (current vs voltage vs power) on this nice data sheet. Also, you will notice that the voltage and power output changes with respect to temperature too.

    Unfortunately, a solar panel is not an ideal battery at all... In fact it is, more or less, a current source. Basically, when a minimal amount of sunlight strikes the panel, it will rise to its operating voltage. From that point on, its output current is proportional to the amount of sunlight hitting the panel.

    How many loads can operate correctly where the load has to set the voltage (say 12 volts) and accept current from 0 to maximum amps.,

    About the only one that does that well is a rechargeable battery. But, for larger systems, you need a charge controller to prevent the battery from overcharging.

    One can design/buy electronics that will collect the varying output voltage and current of a solar panel in an optimum manner and output that power in some useful way. Commercially the MPPT type solar charge controller and the Grid Tied Inverter are two common ways of doing this today. And there is the PWM type charge controller which less optimumly collects the power and can properly charge a battery (less costly).

    But the above are designed for specific applications and tend to be larger devices and use larger panels.

    As others have said, you can buy/build smaller solar battery chargers but they tend not to be very fast chargers. You can look at the size of this C Crane solar battery charger as an example:
    This high powered solar charger charges two Rechargeable Batteries of the same type and size (D, C, AA, AAA). It puts out about 150mah and about 5 volts. All of the other solar battery chargers we tested were unsuitable because their voltage was too low. Weight: 11.8 oz. Size: 6.8" W x 4.5" H x 2.3" D.
    It is a fairly large solar battery charger and has a 150 mAH output. Compare that to the average AA NiMH rechargeable battery with 2,000 mAH of capacity and is around 66% efficient recharging (lead acid storage batteries are around 80-90% efficient). This charger can charge two of them in series (I think), so it would take:
    • 2,000 mAH * 1/150 mAH per hour * 1/0.66 = 20.2 hours to recharge two AA batteries
    Realistically, most people get between 2 and 6 ours of sun per day (that is full sun equivalent hours per day). So it would take roughly 3.5-10 days to recharge a pair of AA batteries with this small charger (depending on season and weather).

    Small solar chargers tend not to be very good chargers. And larger chargers need fairly large solar panels to be useful for most people.

    For example, if you wanted to charge a pair of AA Batteries in one - two hours, you would be looking at:
    • ~5 volts * 2 amps * 1/0.66 =15 watt solar panel
    A typical good quality 20 watt solar panel would cost around $185, be roughly 2' square, weigh 5.5 lbs, and output 1.23 amps @ 16.3 volts.

    Notice that the output is 16 volts at 1.23 amps. Now you need a switch mode power supply to down convert that voltage/current to the ~5 volts and 2 amps needed by the batteries to recharge. And control the current/voltage for proper charging or you have a pair of dead/cooked cells on your hands. If you want to do this efficiently.

    Obviously, there are different models of solar panels out there that may be better for your design--the ones I listed here are intended for 12 volt remote systems.

    A lot of this is pretty straight forward electronics (for simple charge controller) but when you get into MPPT (maximum power point tracking) -- then you need to study about switch mode power supplies and feedback/control circuits.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Makeitrein
    Makeitrein Registered Users Posts: 5
    Re: How to light a bulb?

    Thanks for replying everyone -

    @vcallaway - Is the purpose of the regulator to manage the voltage or current of the solar charger? I'm a tad reluctant to buy the Sunforce system - I would prefer a more hands-on approach to building my first solar circuit.

    @Greenpowermaniac - Cool! Did not know that some bulbs ran on DC. So... what would be the materials I need for this project?

    A small solar panel, light bulb, flux, soldering gun, metal wires... anything else?

    Also, are inverters necessary for electronics that run on AC?

    @BB - That was an especially helpful post. Thank you. The calculations really helped illustrate your points.

    Some questions:
    1. How do I determine the correct level of voltage/watts/current?

    2. What is the difference between the "regulator" that vcallaway mentioned and the "charge controller" that you talked about?
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: How to light a bulb?

    a charge controller is a special regulator made for use in solar, but it can be used as a regulator outside of solar applications just the same. in the case of a regulator for your needs it is simply something to stop the damaging higher voltages so it is a voltage regulator that is needed. some that are familiar with regulators or electronics in general can slap together something simple with linear regulator ics, but i don't recommend a crash course for you into doing that as that may be beyond your hands on abilities.

    edit to add:
    i thought it important enough to make mention that most controllers do require a battery in order to work, but there are some that will not need the battery's presence.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How to light a bulb?

    You can get a 1 amp dual filament 12 volt brake/tail lamp + wire socket from the auto parts store (replacement trailer lamp). Those are something like 50 watts maximum (the brake lamp) and the tail lamp is something like 15 watts.

    Now, a 65 watt panel may cost you $300 new--and you might find some deals out there at $70 (used/closeouts).

    How much do you want to spend on the experiment. You could use an 12 volt LED replacement bulb that only takes a few watts. Obviously, the size of the panel is much less--and so is the cost.

    Or you can go to Radio Shack, get a few 0.1 watt LEDs and some resistors (and probably a blocking diode to protect against wiring the LED backwards) and make up an LED

    Note--solar panels work. No experiments are needed. A lot of people build a simple single panel charger with a single 12 volt storage battery, charge controller, and 12 volt inverter + cigarette lighter socket.

    Then you have something that you can really experiment with--plus it is useful to haul with you camping to run a radio and a CFL camp light... No fuel, generator, or noise.

    Of course, you have to do some math to size the panel, battery, and inverter to your needs. In general, most people over estimate the amount of power available from a solar panel + battery system.

    Typically, assume 50% losses and 3-6 hours of sun per day (winter/summer).
    • 20 watt panel * 50% * 6 hours = 60 Watt*Hours per day.
    A 13 watt CFL will run:
    • 60 WH per day / 13 watts =4.6 hours of light per charge in summer
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vcallaway
    vcallaway Solar Expert Posts: 157 ✭✭✭✭✭
    Re: How to light a bulb?

    The regulator in the sunforce is voltage.
  • Makeitrein
    Makeitrein Registered Users Posts: 5
    Re: How to light a bulb?

    @Niel - Thanks for clearing up the confusion.

    @BB. - Lots of good ideas there! And thank you for including some suggestions of things I can do! I noticed that you live in the SF Bay Area. I live in SC County. Do you know of any stores where I can buy small-scale solar equipment locally?

    I would prefer to keep my experiments in the range of $30 or so. Because my town has a local Radio Shack -- I'll try to power a LED bulb as you suggested.

    I'll start off with a simple direct drive. Something like this:

    2964148148_275420e656.jpg

    I'll add the diode as I become more familiar with the system.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: How to light a bulb?

    Most LED diodes run about 2V and 20milliamps. To a PV panel, they will look like a piece of wire, and will flow the entire panel current thru them, at about 40 mA, they fry and stop working.
    I'd suggest a tail light (not stoplight) or a side marker light from a car. Those are low power, and should light fine from a >20W panel.

    A fluorescent bulb is out. Incandescent is the way to demo this.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How to light a bulb?

    LED's are non-linear devices and really need to be fed a constant current to be happy.

    A 20mA LED (red is the lowest voltage) would work with a couple volt panel rated:
    • 0.020 amps * 4.5 volts = 0.1 Watt 4.5 volt (or higher) panel
    Remember that the output current of a solar panel is pretty much based on the amount of light hitting it. Less than full sun, will be less than full current (LED will dim/go out).

    Otherwise, you have to do the old ballast resistor calculation and look at the operating current/voltage spec. of the LED you want to light. Here is a nice link to understand more about LED's and how to power them.

    Have you taken any beginning electrical / electronics courses yet? A good course or book+lab for home study would be very helpful. The concepts from a 1-2 semester type course will learn will teach some 90% of what you need to know with solar and home wiring basics.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tvengineer
    tvengineer Solar Expert Posts: 31
    Re: How to light a bulb?

    A DC motor or small DC Fan is a good starting project...

    I have exactly that to blow a little air around my batteries..

    I dont' know if you have a Harbor Freight store near where you are.. but they sell some 1 watt thin film solar panels for around $20 each.

    I have three of them in parallel running a DC fan from an old computer power supply..
    they really need direct full sun to get the little fan going .. but it does work..

    I got them thinking I would make a ventilated HAT ;-)

    I did have to experiment around in a large junk box of fans at work to find the one that used the least amount of current though..

    but your little diagram of the solar panels directly hooked to a DC motor will work like my setup....

    Now.. if you can find a bigger panel.. you can run a bigger fan..
    I have a 20 watt panel directly connected to a RIOBI work fan (available at HOme Depot for around $30) The Riobi fan is designed to work on an 18volt battery..
    I simply hooked it to a 20 watt panel and it really blows a LOT of air in bright sun..
    It slows down but continues to run even in very cloudy days..
    I use it to ventilate my attic.
  • Makeitrein
    Makeitrein Registered Users Posts: 5
    Re: How to light a bulb?

    @tvengineer- No Harbor Freight, but we do have an Ace Hardware. I'll check it out.

    And I like the idea of a ventilated hat - could keep your hair nice and cold. 8)

    @mike - Thanks for telling me that 'fore I blew something up.

    @BB - Ordering electronics book ASAP from Amazon.
  • System2
    System2 Posts: 6,290 admin
    Re: How to light a bulb?

    Radio Shack has a Solar 'kit' - that has a small solar cell, and a small motor. It is a great way to see a cause and effect using solar. While the solar cell is too small to do anything useful - it is a great learning tool.
    Regards,

    James Jackson