Let's Make Robots!

Review: Solarbotics Zendulum


It's time to find a sunny spot in the house, put on some chillout background music, light some aromatic candles, all in all prepare to get in a Zen mood :)

Ready? Good. The last missing piece is the Solarbotics Zendulum to complete the scene:

From Zendulum

Part 1: Yey package arrived!

The postal office notified me I had a package, so I went to pick it up and found:

From Zendulum

Of course I could not help myself in opening it before taking a picture, but be assured it was in pretty good shape.

On the inside everything was very well protected, so the kit made it trough the long trip without any problems.

From Zendulum

Part 2: The Kit

Inside the box, I found:

From Zendulum

The inventory contains:

  • A printed manual
  • Laser cut acrilic parts for the case including a spare rail 
  • The PCB and the required parts
  • A magnetic ball
  • A nice letter from Solarbotics :)

All parts are there, nothing is missing.

Part 3: Instructions and Assembly

The included manual is very detailed and beginner friendly. It contains five sections describing the tools required to build the kit, a part list, a soldering tutorial, the actual building instructions including trobleshooting and finally the schematic with explanantions on how it works. An electronic variant of the manual is provided on the Zendulum page on Solarbotics  in the Resorces section, in case the printed manual get's lost. 

Assembly of the Zendulum is a simple and fun task, especially for the beginner doing this for the first time.

The PCB is very good quality and I had no issues soldering the parts, it comes with a black finish and white silkscreen making parts locations easy to find.

Mounting the case however requires attention, as the manual states: "acrylic is about as strong as same-thickness ice". This means the it can snap very easily under pressure, so if a part does not fit, DO NOT apply force, get a file and file it down a little.

Having the above in mind  it should take about 5  to 10 minutes to have the case completed, probably about  1 hour for the PCB if this is your first one.

This is how it should look when mounted:

From Zendulum

Part 4: Closer to Zen with the Zendulum

So far I guess anyone reading this review must be thinking something like "Zen ... Zen ... OK, OK but what is the Zendulum actually do!?" 

Well Solarbotics describes it as follows: 

"The Zendulum is a do-it-yourself, simple solderable kit. It features a spherical neodymium rare earth magnet, which emulates Newton's cradle when infrared irradiation is applied. 

In English? There's a magnetic ball that rolls back and forth when powered by a solar cell."

So when it is powered up either by the solar cell or trough an usb cable, the circuit charges the two big capacitors, then the charge from one of the caps is released on the coil causing the magnetic ball to move up it's rail in one direction. As it rolls back over the coil it generates voltage trough induction causing the circuit to release the stored energy in the second capacitor but with reverse polarity, pushing the ball in the other direction. This goes on and on as long the circuit has power so the ball is kept moving.

Pretty cool I would say :)

I have tested it both in the sun and USB powered, see the videos below, sorry for the weird angle on the sunny one.

Part 5: Conclusion and final thoughts

The Zendulum makes a nice weekend project. It is real easy to put togheter and a great startup project for the beginner but also fun for the more experienced users. 

One observation I have to add is that due to fact that the Zendulum employes a magnetic ball (a pretty strong rare magnet ball actually) the presence of ferrous metal or EM fields around it has a pretty big impact on the way it works. Also the place where you put it has to be as level as possible. This is actually mentioned in the manual I'm only emphasizing it with my own experience.

As you can see in the sun powered video it moves the ball pretty much erratically as it was put on the table of my CNC. Unfortunately that's about the only place in my flat where I get sun and it is more or less level. On the other hand, powered on USB on my desk worked wonderful :)

Another note keeping in mind the above, I could not get it to work at all using any other light source besides direct sunlight, while the manual mentions it could work also with halogen and incandescent light sources. On the other hand my only halogen light is real small and I don't have any real powefull incandescent bulbs either :) 

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Yes you definitely mentioned it, I think I missed it on the first read through and just focused on the video where it looks like it doesn't work under solar power....sorry. I guess I just wanted to clarify with the LMR viewers that it does work under solar power but as the the video shows, it has a hard time when there is metal present nearby. My bad.

Hey TinHead thank you for the great review!

I like the note about filing down the parts that don't fit, we may just have to add that into the next revision of the manual, along with a circuit diagram fix we've been meaning to add for a while. The only addition that I'd make to this awesome review is to say that the Zendulum should be placed away from any large metal objects when relying on solar power as it doesn't have a ton of power when using the Solar panel. In your video the magnet seems to be quite effected by the large metal objects around it, such as those bolts in front of it. I ran into this issue myself quite a few times as I vastly underestimated how large of a field that rare earth magnets actually have.

Thanks again for the sweet review post!

I think I have mentioned the "keep away from metal parts" thing in the conclusions part. Do you think I should emphasize it more strongly?