ROBOBUGS.NET - Techniques

A good way to mount your solar panels without destroying them is to use servo tape. Servo tape is a super sticky double-sided foam tape used in radio-control models. This stuff is so sticky that you almost can't remove it. However, with some careful twisting of the two joined parts, the tape can be removed without ruining the solar panel. I've read a bunch of articles in which other folks have used super glue or epoxy to mount their panels. This method will certainly be strong enough but you could easily destroy the solar panel trying to remove it. I try to make sure my panels can easily be swapped or moved into another robot later. Another thing I try not to do is glue the wire to the panel after soldering it on. Instead, I keep the wire as thin and flexible as possible and mount the wire to some other nearby structural point. Solar panels simply cost too much to take any chances on tearing them apart while replacing wires or removing them from their mount. Servo tape can be purchased at Tower Hobbies or other R/C stores.

In the above section I discussed the use of servo tape for mounting solar panels in a semi-permanent manner. This section is describes a much more solid mounting method which is still easily undone. Some people really like the solar panels to be mounted with glue or epoxy. The downside to that method is that the panels can easily be damaged trying to remove them. On my robots I just cut out a piece of an old circuit board about 1/4" by 1/2" that has alot of copper on it and glue it to the back of the solar panel. Now I can simply solder it to the frame of the robot. This way the panel can easily be removed by melting the solder and pulling it off the frame. Even if your robot doesn't have a frame or body made of paperclips, it is still much better to glue a paperclip to a capacitor or other solid part and attatch the panel that way. It's generally alot cheaper to buy a new capacitor than it is a new solar panel. There are some photos of this mounting technique in the Ole Yeller section for your enjoyment!

My solution for those who glue their wires to the back of the solar panel is this. Use a section of an old circuit board with a couple of wire traces on it and solder the wires from the solar panel outputs to the traces on the board. Then solder wires from the board to your circuit. The important thing is to keep the wires from the panel to the board as short as possible. That way there's not enough wire to get caught on anything or to vibrate and pull the solder pads off the solar panel. Neat huh :)

Solar panels have sharp edges. After all, they're glass. I like to cover these edges to prevent any chance of getting cut. I use an x-acto knife and slice the insulation off some 16 gauge wire by slicing it along the length of the wire. Then pull the wire out through the slice and trim the insulation to the length you need to cover one edge of the solar panel. Use crazy glue and carefully glue this insulation to the edge of the panel. It will take some practice to get the insulation to slip onto the edge of the panel and especially when the glue is on it. I recommend sliding the insulation from one corner and pulling it across the edge. This only works when actually gluing if you can do it really quick. Another thing to try is using some fine scissors to snip a small bit off the slit in the insulation. This will open the slit up a little to ease installation. The size and color of the wire can be suited to the color or design scheme of your robot. You can see examples of this technique on many of my robots.

When building robots, the roboticist is faced with many challenges. This section deals with selecting and using different types of glues properly and safely. The first one I'll discuss is Super Glue. This glue has a nasty reputation for gluing your fingers together or gluing your fingers to the piece your working on. The main ingredient in Super Glue is called Cyanoacrylate Ester. If you have trouble, as I did, even saying Cyanoacrylate, try breaking it down like this: Cyan-o-acryl-ate. For your safety I strongly recommend checking out the Material Safety Data Sheet (MSDS) for this chemical HERE. I always keep a bottle of De-Bonder close at hand when working with Super Glue. De-Bonder is available at Tower Hobbies and at many other hobby supply stores. In a pinch you can also use nail polish remover (with acetone in it). I use Super Glue when building as first glue step. For instance, when I have to glue many transistors together in a block arrangement, I'll glue them together in sets of two and then glue all the sets together. After the glue has cured (and I unglue my fingers), I'll then use a toothpick and apply some 5-Minute epoxy in the spaces between the transistors. 5-Minute epoxy is a much better glue for structural use. Super glue is not well suited to uneven surfaces or small contact areas where gap filling is required. Super Glue is excellent for very clean breaks in glass or other smooth tight fitting pieces. This is why I use it only as a way to hold pieces until I can apply Epoxy. One of the great things about epoxy is its gap filling ability. You can fill some pretty ugly holes with Epoxy and a little patience. You can even completely encapsulate circuits in Epoxy to prevent vibration damage or to make them waterproof (this also makes them repairproof though). This chemical has its precautions however, and I recommend looking up the MSDS for the specific type of Epoxy you will be using. There are simply too many different kinds to list here. If possible, I recommend wearing thin latex gloves whenever dealing with either type of glue discussed here and NEVER EVER EVER LEAVE THESE OR ANY OTHER GLUES WHERE CHILDREN CAN REACH THEM! A little common sense goes a long way.

Here's a neat effective way to make tires for your robot of any size you need. First, get some silicone fuel tubing from Tower Hobbies or your local R/C hobby shop. Then cut a short (1/4") length and slip it over one of your Dremel tool's straight shafts. You know, the ones used for sanding discs and cut-off wheels? Then put on your safety glasses and turn the Dremel on. Now use some sandpaper and gently rub it on the silicone tubing. Keep doing this until you get the desired shape on the tubing and then turn off the Dremel. Repeat this procedure for the other wheel too. Now you have a set of miniature tires you can slip onto your motors! Don't worry about the inside diameter of the tubing because you can always shim the motor shaft with some heat-shrink tubing or wire insulation.

Here's a cheap way to make tactile sensors in a pinch. Grab yourself a couple big paperclips and cut off 2 pieces about 1 1/2 inches long. Now take some heat shrink tubing that fits the paperclip and cut off 2 pieces about 3/8" long. Now, slip the heat-shrink tubing over the paperclip and heat it up. Don't worry about the position of the tubing at this point. We want it to still slide so we can set-up the sensor later. Now get some flat spring material from a pull-back toy car or some old wind-up toy (not your kids toy though!!). Take the wire and cut and bend it into the shape you want leaving about 1/2" for attachment to the paperclip. Now find some larger heat-shrink that will fit over both the paperclip (with HS tubing on it) and the flat spring material. Cut off a couple pieces about 3/8" long. Now solder your wire to the end of the spring material where you will make the electrical connection and lightly sand the area of the spring that will contact the end of the paperclip. Ok, are you still with me here? Now, shrink the tubing over the paperclip and spring together being careful not to burn your fingers. The spring and paperclip should not be touching. That's pretty much it! To tune the sensitivity of your sensor, just slide the paperclip in and out of the tubing until the spring is almost touching it. When you get it dialed in the way you like it, you can apply a small drop of superglue to the tubing and paperclip to keep it in position. The paperclip can easily be soldered directly to the frame of your robot for solid mounting!

One more note about tactile sensors. If you make the standard small spring type of sensor typically used, find yourself some old push-button pens. I have found that these springs are the easiest to solder to.

If you need to stack your chips for more power handling, you shouldn't need to solder each and every pin to pin contact. That much soldering could cause premature chip failure if you're not careful or you get in a hurry. Instead, simply squeeze the pins together just slightly, press fit the chip onto the first chip, and solder the diagonal corner pins. You should choose the diagonal corners that are the power supply pins. Even though the pins are not all soldered, you should get many years of reliable service.