Archive for the 'Solar' Category

We conclude our DIY project ‘Make your own Solar Bag’ by sharing with you our experience by using our Solar Bag for a month now in many different ‘real life’ situations to give you an idea what you can expect (and what you can’t expect) from the solar charging power of solar bags.

We can only speak about the performance of our bag but I would expect that most of the bags using a similar solar panel will have the same performance. Our DIY Solar Bag does not have an on board battery to store energy like many other commercially available Solar Bags have. We plan a version 2.0 of our bag where we will add this function but for the first project we wanted to keep it simple.

Using a solar bag makes of course the most sense when the sun is showing its full face and you plan to be outdoors and not hiding in the shadow. The solar bag will charge behind windows as well as in overcast conditions but the generated power will be less and with it the charging time will go up. How much depends on the actual light conditions.

Walking around in the city on a sunny day gave very good results because of the additional light coming from reflections off glass and bright stone walls. The charging went down when walking around the park with many trees and lot of grass. Going in and out of the trees shadows causes the iPod or cellphone to switch between charging and not charging (in the shadow) that might actually train the battery because each time when the charging starts or stops the display will be switched on which uses quite a bit of power.

As far as I know (but I am not an expert in battery chemistry), the battery will not be damaged or loosing the performance of it by the frequent change of charge and not charging.

If your solar bag is not exposed to the sun for about 70% of the time, I would recommend not connecting the iPod other USB powered devices. In such cases where the sun exposure of the solar bag is less then around 70%, a storage battery would be more effective.

We went also to a beach with our Solar Bag where it could show its full performance, loading at the maximum speed due to lot of reflection from the sand and water. Going to the swimming pool got us similar results of full speed charging. We are far away from any snowy mountain to test our bag but my guess would be our Solar Bag would run there on high speed as well due to the high reflection of snow.

Generally, reflection is not needed for the solar panel to work in overdrive. If the bag is facing the sun fully will give the best results. By carrying the bag like any other bag, the sun is not always fully hitting the solar panel and reflection of the surroundings do help to improve the charging performance.

Although you can recharge a complete empty iPod (G5 for example) in about 6 hours, I do not see a solar bag as my primary charging station but appreciate the convenience to have additional power to top off my energy hungry devices.

Having some additional, free of charge power trickling into the iPod while outdoors (on sunny days) helps extending the playtime. Great and useful when being outdoors on the beach or pool, going on sight seeing tour in the city or exploring the wilderness. As long as there is sunshine the power will be yours.

To place the (sun) power in your hands (bag), you can do the following:

• Follow our guidelines on how to make your own Solar Bag part one and part two
• If you do not have the time to make your own Solar Bag we can offer you a complete functional Solar Bag (the second bag we made to make all the photos) on our Etsy shop
• We made some additional electronic boxes available on our Etsy shop if you want to spend all your time on the bag design but not on the electronic part
• More photos of our finished bag can be found on Flickr to get you inspired with your own design

We hope our first DIY project is helpful for your own experiments and creations. If you have any questions on how to make your own Solar Bag or about our experience of using a solar bag, just drop us a line into the comments and we will be more than happy and share our wisdom

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Today you will make your own Solar Bag complete with the guidelines for the electronic part of our project.

A few words to the design: The following electronic concept is based on the DIY instruction from Popular Science but we added a diode which is recommended by our Solar panel supplier Sundance Solar.

The diode protects the solar panel from damage in case current is flowing from the device back to the solar panel. This can happen when device is connected to your bag but the solar panel is not active, meaning no sunshine to let the solar panel work.

Let’s get started with the shopping list, we recommend using Digikey, a very reliable online shopping source:

1x 78M05 Voltage Regulator (Digikey part here)
1x 0.47µF 50V Electrolytic Capacitor (Digikey part here)
1x 0.1µF 50V Tantalum Capacitor (Digikey part here)
1x 20V 1A DO-41 Schottky Diode (Digikey part here)
1x 1.3mm DC plug (Digikey part here)
1x 1.3mm DC socket (Digikey part here)
1x Copper glad PCB, 3″x4″ (Digikey part here)

1x Plastic box at least 2.8″x1.8″x0.8″, any type you can find will do
1x USB female connector (cut off from an USB extension cable at a length of 20cm)

You will need the following tools: solder, a solder iron and I strongly recommended a multi meter. A simple one is fine, you do not have to buy a high end multi meter for our simple electronic.

The image below shows the connectors we use: on the left side is the DC-socket that goes on the printed circuit board and next to it is the DC-plug that is soldered to the power cable of the solar panel. Connect the positive wire of the solar panel to the center pin of the DC-Plug and the negative wire to the outer part of the DC-Plug. Use the same polarity for the DC-socket on the PCB.

In the center and the right image show the cut off female part of an USB extension cable. Open the cable end and separate the four wires: red, black, green and white. The green and white wires are USB data lines we do not need, cut them off. Strip off a few millimeter of the red and black wire for soldering to the PCB.

Next we take the plastic box (see image 1) that will hold our small PCB and give support to the USB cable and the DC-socket. Drill two holes, one just large enough for the USB cable, slide the cable in and make a knot for a strain relieve to the solder points of the cable (see image 2). The second hole is for the DC-plug to fit (see image 4). In image 3 you see the PCB before and after we cut it down to just fit into the box. The PCB should not move around. If your box is bigger than your PCB, glue it after everything works into the box.

Image 5 shows how all the components have to be connected to each other. Watch out to have the correct polarity! The positive lead of the 0.47mF electrolytic capacitor is soldered directly to the Input of the voltage regulator. The positive lead of the 0.1mF Tantalum capacitor is soldered to the voltage regulator’s Output. Finally, the negative leads of both capacitors are soldered to the Ground of the voltage regulator. Connect the positive lead of the DC-socket to the negative lead of the Diode and the Diode’s positive lead to the input of the voltage regulator. The negative lead of the DC-socket is connected to the Ground of the voltage regulator (see image 6 and 7). We used so called jump wires to make the connections on the PCB.

Solder now the red wire from the USB cable in the box to the Output of the voltage regulator and the black wire to the voltage regulator’s Ground.

Now comes the most important task: measure if all your connections are correct. We have here a ’secret’ trick to avoid having to go out to the sun with your solar bag to verify your work. We used a battery box (available in many electronic shops) that holds 4 AA batteries (see image 8). We have soldered a DC-plug (same as we used on our solar panel) on the battery box and can now connect the battery box to our Solar-USB-charger electronic. Those 4 AA batteries give 6 volt (4×1.5) and 1400mAh, much more current (mAh) than our solar panel but the voltage regulator will cut this off at the maximum allowed for USB2.0 at 500mAh.

Connect the Batteries or the solar panel (if you have sun shine right now) to the electronic box and test the voltage with a multi meter at the voltage regulator input and on the USB connector wires. The reading at the first point should be approximately 6 volts. The value at the USB wires should be 5.15 Volts (see image 9). If everything looks correct, you can now connect your iPod or any other USB chargeable device (see image 10).

Our electronic design will charge any device that can be charged via a USB connector and is USB standard compliant. That means USB devices that do not follow the USB standard will not charge (like the Motorola Razr V3). Our recommended solar panel delivers under maximum sun exposure around 9 Volt by 250mAh (the nominal values are 7.2 Volt by 200mAh). The USB1.1 standard specifies 5.15 Volt and 100mAh for power supply to devices. The newer but already very common USB2.0 standard has the same voltage put allows up to 500mAh. That means our solar bag will charge in full sun twice as fast as a USB1.1 connector on a PC and half the speed of the USB2.0 connector on a PC.

We selected this simple concept as our first DIY project because it is easy to make with very common components and low cost. Of course, adding a battery to store energy for rainy days is something we do have in mind.

Our DIY Solar Bag 2.0 is on top of our to-do list, so come back soon and see how we make it.

For now we wish you lot of sunny days and we like to hear from you in our comments how your solar bag is helping you to stay entertained and connected all the time with green, environmental friendly energy.

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A few days ago we started writing about our DIY Solar Bag and today we start to show you how to make your own solar Bag ‘the easy way’. Part one is about the integration of a solar panel in a bag.

What you will need for this part of the project:
A bag. Either you transform one of your bags or you look for a new one that looks cool and has a design that makes it easy to integrate a solar panel. The later was the way we choose.

A solar panel. Our recommendation is the PowerFilm WeatherPro Solar panel 7.2 volt 200mAh which costs $ 56.95 from Sundance Solar. This company was also the best in terms of service and quality delivered.

Some small stuff that can be found in stationary shops, needle work and hardware shops: Sctoch double sided tape #668 from 3M around 2cm wide, vinyl tape to cover the solder points, around 1m two wire cable (we used the multi stranded type around 1mm in diameter each to have a soft feeling) and Textile glue.

Before cutting a hole in your bag, a few words on our design: We wanted the solar panel integrated as seamless as possible, it should look as the bag was designed with a solar panel in mind. We decided to laminate the solar panel to the fabric of the bag, no stitches visible.

We begin by marking the bag where the hole of the size of the active area of the solar panel will be (you will see easily what we mean with the active area when you have the solar panel in front of you) and cut the hole out (see images 1 to 3).

Prepare the solar panel by soldering the cable to it (see image 4). write down which cable (color) you connect to the plus terminal and the minus terminal. Which is plus and minus is shown in the data sheet that comes with the solar panel.

The solar panel has around 2cm of additional plastic area outside the active solar cells, this is the area we use for lamination. For reliable and strong lamination, clean this area very thoroughly with a soap solution or window cleaner.

Apply the double sided tape on the cleaned edges of the panel (see images 5 and 6) and rub them with your fingernail as hard as you can on to the solar panel (see image 7). Wrap a good share of vinyl tape around the solder points to insulate them and give support (see image 8).

The solar panel is now ready (see image 9) to laminate to the bag. But before you do this, decide how you will guide the power cable through your bag to a place where the electronic box the size of around 7cm x 5cm x 2cm will be.

Slide the solar panel through the hole into the bag and don’t forget to guide the power cable at the same time inside the bag (see images 12 and 13). Take off the protective paper of the double sided tape one by one and place the solar panel to match the hole you cut out earlier. Apply pressure to ensure the panel stays in place first. Then use a piece of cloth like linen and use again your fingernails to force the fabric on to the glue of the tape. The linen will avoid rub marks from you fingernail on the bags fabric (see image 11).

You are almost done. Check if the edges of the cutout around the solar panel are clean and no loose treats are there. Cut them off if needed. Apply textile glue around the edge of the solar panel cutout. The textile glue is used for seaming the edges of the fabric and can withstands wear, tear and washing - perfect for our design.

You can now reward yourself with a good cup of tee or coffee. Next time we show you how to make the electronic part which is much easier than modifying the bag.

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