Introduction: Solar Cockroach 2.0

By BrownDogGadgets
About: I used to teach middle school science, but now I run my own online educational science website. I spend my days designing new projects for students and Makers to put together.

It’s been a while since the original Solar Cockroach went extinct due to scarcity of parts, and the Solar Cockroach 2.0 took its place. Since that fateful day, the cockroach has continued to evolve based on user feedback and part availability. The motor has been replaced again, this time featuring an adhesive backing, and paperclips are now used for legs.

This instructable will detail how to put together the Solar Cockroach 2.0, a simple vibrobot made from a 2V solar cell and vibrating motor. This is a simple and fun project, though it does require the use of a soldering iron and hot glue gun. You can easily source your own parts, or check out our kits over at BrownDogGadgets.com.

We also have a non-soldering version of this project, the Solar Bug Kit. The Solar Bugs feature a laser cut wood body and pipe cleaner legs. Solar cells with attached motors and pre-cut leg holes mean you don’t have to worry about hot glue or solder.


Time: 15-30 minutes
Cost: $5-10
Difficulty: Easy

Step 1: What You Need

Supplies:

Grab a Kit

OR

1x 2V Solar Cell
1x Vibrating Motor
2x Big Paper Clip
2x Googly Eyes
6 inches of Magnet Wire

Tools:
Soldering Iron
Solder
Hot Glue Gun
Wire Cutters
Helping Hand - (optional... but handy)


Sourcing Your Own Parts

We learned a few lessons as we were sourcing parts for our solar cockroach kits, which we are happy to share. This section will be most useful for those sourcing their own parts, if you are building from a kit, feel free to skip ahead.

Where to buy:

You can find these solar panels and motors all over the web. eBay has quite a few people selling them in bulk. You can use any cell you want, but the big factor is the size. The 2V rectangular cells work well in this case, though a small round cell would be fun to turn into a Solar Ladybug.

Motors can be bought in various sizes or shapes. Alternately, you can steal the vibrating motor out of an old cell phone or pager. This will save you $2.

You can also find individual parts for these kits on BrownDogGadgets.com, in case you're only missing one or two pieces. Feel free to contact us about discounts for educators or large orders.

What to look for

Solar Cells:

As mentioned on the parts list, you can use any sort of solar cell for this project, however, there are some things to keep in mind. While you can find heaps of different types of solar cells on the internet these days, not every cell is equal.

As we're using small motors, we're going to need a certain amount of power. I've found that most of the little vibrating motors you buy online need at least 1.5V and 30mA to trigger. We want our solar panel to go above and beyond that threshold. When solar panels are rated, they're given a rating at their max power level, which usually means noon on a sunny day. As these conditions don't exist all the time, we have to expect that our solar cell will usually be operating at a lower power level than what it's rated for.

The second thing to keep in mind is the size of the solar cell in relation to your motor. The bigger and heavier the cell, the stronger the motor you'll need to get it moving, the stronger the motor, the more power it will require... And on and on.

The key is to find a solar cell that is both small and has a good kick behind it. Salvaging solar cells from old garden lights has worked for us in the past, though often times they lack the current to get the motor started. The ones we prefer to use are some long and skinny 2V 50mA solar cells. They're cheap and easy to find online from quite a few places.

Motors:

Small vibrating motors can be found everywhere, and you probably have several in your house right now, if not in your pocket. Common electronics such as cell phones, pagers, video game controllers, and electric toothbrushes all make use of these types of motor. You can easily scavenge broken or obsolete items for their motors, though you will find a large range of sizes. As with the solar panels, you have to hit the sweet spot between too large to turn on, and too small to move your roach.

Questions to ask your motor before you buy it:

1) Do you have soldering points?

You want a motor (and panel) either with wires, or large enough tabs to easily solder to. You don’t want to wind up with a motor you can’t connect to your panel.

2) Do you meet my power needs?

You need a motor that is rated to work at a very low voltage, aim for 1.5V. Most will do this just fine but we've occasionally run into some that need 2.5V or even 3V. Also remember that you need a DC motor, not AC.

3) Are you strong enough?

You can buy some really small vibrating motors, but they're not going to be strong enough move your roach. Usually the ones that are 15mm - 20mm long will do the trick.

4) Are you too expensive?

If you're paying more than $3 for a motor you're paying too much, especially when you figure in that shipping is never free. Just buy one off one of the websites above when you're buying some other hobby items. Find a couple of little projects on instructables and make an order. It saves on shipping.

Step 2: Video Instructions

In case you're a visual person, or honest with yourself and just too lazy to read, here are video instructions for the Solar Cockroach!

Step 3: Soldering

Remember to heat up your soldering iron and hot glue gun so they are ready to use when you need them!

Solder your motor to the solar panel

Some solar panels have multiple leads. You can test your motor placement by holding the panel in the sun and pressing the wires to different combinations of leads until you feel movement. Alternately, use a multimeter to test for resistance between leads. You want to use two leads that appear to be an open circuit, not two leads that appear to be a short circuit.

Lay your solar cell down, and align the wires from the motor with the leads on the solar cell. It does not matter which wire goes to which lead, the motor will spin either clockwise or counterclockwise depending on how you wire it. If you have one of our kits, your motor comes with an adhesive backing on one side. Make sure your wires reach the contacts before sticking down the motor.

Place your soldering iron tip so it is touching both the wire and the solder point, while keeping your solder on the other side. Touch the end of the solder to the terminal, and it will melt to make the connection. It can be helpful to arch your wires before soldering to prevent them from springing away once the soldering iron is removed, and before the solder has a chance to harden. Repeat this step for the other wire and terminal.

Once cool, turn your solar cell over just to make sure everything is well connected. If you like, you can go outside and test it out. If your motor doesn’t vibrate when the solar panel is exposed to bright sunlight, you may have a poor connection, or you may have soldered to the wrong terminals.

Step 4: Making the Legs

Use your wire cutters to cut two paperclips in half, which should leave you four pieces with a U-bend in the middle, and a hook at one end. Cut off these hooks to even out each piece. Each U-shaped paperclip half will become one pair of legs, with one leftover (unless you want to make a spider instead!).

Tip: Bending the legs outward before gluing makes it easier to use the glue gun on the third pair.

This is a good time to get out your helping hand, if you have one, or con a friend into holding very still. Put a drop of hot glue on the bottom of the solar panel and stick the U-bend of two pairs of legs into it. You have to hold the legs while the glue cools and hardens, but after 30 seconds or so you will be able to let go. Watch for the glue to go from clear to cloudy for a clue that it’s almost done. Place a third pair of legs on top of the first glue blob, and add another drop of hot glue on top to keep them in place.

How long your legs are, what angle they are at, and where you use the long and short pieces are all up to you! Make several styles and see what works best.

Step 5: Dress Up Your Cockroach

Right now you technically have a functioning solar cockroach. Outside in the sun he will vibrate and dance around like all the other little cockroaches. But he’s missing some important parts!

Attach the Antenna

Fold your lightweight wire in half and place it in the front middle of your solar cell. Apply hot glue and allow it to cool and harden before moving your cockroach.

Attach your Googly Eyes

Place a drop of glue onto the front of your roach, next to the antenna, then carefully use a googly eye to smear the glue and move it to the front. This way the eye faces forward, but is securely attached to the panel. Repeat this step with the second eye, and you’re done!

Step 6: Enjoy!

While googly eyes and antenna are not required for your roach to function, it sure looks a lot cuter now! Feel free to give it some more flair with bits of paper, spare electronics, or whatever you have laying around. Here at the shop we’ve made some with laser cut acrylic heads, LED eyes, and diode legs, which look pretty cool. Keep an eye out for our Solar Cockroach 2.0 Deluxe kits featuring these upgrades!

We hope the guide and video are helpful for those of you looking to put together our kit, or to assemble a Solar Cockroach from scratch. This project is super fun to make, and a great “first robot” project for kids.

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