By adding another diode and capacitor we can generate negative output voltages as shown in figure 5. Capacitor C 1 and diode D 1 level shift the positive peaks of the voltage waveform at pin 1 and clamp the voltage seen at the junction of D 1 and D 2 to a diode above ground.
This now negative going waveform is rectified by D 2 and filtered by C 2. Figure 5 Negative voltage generator. The datasheet includes a table listing the output current at a V DD of 1. L 1 Inductor value. Output Current. Another option is to replace the simple inductor with a transformer. The Coilcraft Hexapath 6 winding HPHL has a winding inductance of uH so it fits right in the range of values listed in the table.
Appling a pulse width modulated square wave could serve as a way to change the brightness of the LED. Adding a voltage comparator to drive the CE input with feedback from the boosted output adds regulation to the circuit as in the DC-DC converter Lab Activity. The regulation scheme proposed in the Lab is more complex but a simpler version can be made by adding just a couple of resistors and an NPN transistor to figure 4 which demonstrates the concept. Figure 7 shows the additional circuitry.
Figure 7 Adding negative feedback regulates the output voltage. The multiplication factor N is set by the resistor divider ratio. The load regulation is fairly good up to the maximum current based on the chosen value for L 1 however, the temperature stability will be rather poor because of the strong negative TC of V BE.
As always I welcome comments and suggestions from the user community out there. Hi Doug, I appreciate this is an old post but i'm looking at modifying my own garden lights that use this chip and was hoping you could help with a question I have. Will it recognise the low current from the solar panel and switch the current to the led circuit but find no draw and revert back to the charging circuit? If it does that and because it is now dark outside will the circuit then drain the battery because the solar panel is now acting like a resistor?
Sorry if my explanation is poor or uses the wrong terminology i'm probably a little out of my depth being on this page. All help is appreciated. YMMV, maybe considerably; I have no idea who or how many companies make them. A Some documentation I have found says that it should work from 0. To get the most of your solar lights, let the solar lights face the sun for several cycles, discharging them overnight.
This will ensure they last as much as possible. Before you set up your solar lights, replace the batteries. Manufacturers usually use low-quality batteries, which makes it seem like the lights are dysfunctional. Just replace the batteries and it will work out well for you! Speaking of batteries, you can charge batteries for other devices by connecting your battery charger to your solar lights. Might as well get as much energy from the sun as possible!
By removing the shades that sit on top of the solar lights as decoration, you can let the panels capture a little more light, which means more energy for you. Solar lights usually have a tiny sensor that tells the lights to turn off when the sun comes up. If you have chickens, using solar lights in the coop can increase their production of eggs. The more daylight the chickens experience — artificial or natural — the more eggs they lay. Keep a few solar lights in storage just in case.
Using a DIY method, you can change the color of your solar lights and potentially increase their battery efficiency. Dirt can get on your solar panels, which will block sunlight from getting in. I purchased several of these little solar garden lights from Walmart for 97 cents each. From past experience I know that if you can get these to function for more than a month, consider yourself very lucky. The light output is very weak, and the rechargeable batteries they put in these are the cheapest they could find.
They figure if they only charge 97 cents, it's easier to just buy more replacements than it is to complain about it. Instead of buying more replacements, or complaining, I decided to go a 3rd route and make them function better by replacing two of the components that make them so cheap.
I replaced the sad little white LED with a brighter and yellow LED to get some decent light output, and I replaced the cheap battery with a better quality rechargeable Ni-Cad so they would last much longer. The clear plastic lens separates easily from the main black housing by twisting them apart. The housing will come apart into two pieces when you remove the two screws. The circuit board is or should be held in place by a bit of silicone adhesive.
Pry this loose with a flat screwdriver and the circuit board should come out easily. Remove any excess bits of adhesive. Get your fine tip soldering iron and some braided wick to remove the old LED. You can get by without the wick, but using the wick to remove excess solder makes this much easier. Some of these lamps have little sleeves covering the leads.
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