Friday, July 9, 2010

Spunky the Photopopper

Spunky, the Photopopper, a BEAM robot

Vital Stats
Weight: 19.7g; Size: 7cm length x 7cm width x 4cm height
Fred Solar Engine with 7600uF capacitance
Powered by dual Solarbotics 24x22mm solar cells

File this one under "stuff everyone else has done so I guess I better do it too."  I build this little photopopper several months ago. I'd been wanting to put together a BEAM photopopper for awhile -- I pulled most of the parts together about three years ago (ouch!). It was supposed to be a simple first project to get my feet wet in building robots. Oh well.  Better late than never, I guess.

For the first attempt, I followed Ray Diaz' tutorial for building a FLED (Flashing LED) photopopper using Ben Hitchcock's Fred Photopopper circuit, but with a few minor layout changes. Following my own advice, I prototyped the FLED solar engine on a circuit board and tested it out then built the photopopper you see here.

The power source is a pair of multi-cell 22x24mm Solarbotics solar panels that are replacement for the no-longer-available Panasonic BP-243318.  Motors are pager vibrator motors sourced from one of the online electronic surplus sites. Of the two types I had only this smaller one actually worked.

Removing the crimped weight from the motor shaft was a matter of cutting a slot in the middle of the weight with a rotary tool and using a vise to pinch the two halves together at the slot, which un-pinched the motor shaft.  Works like split shot fishing weights. A pair of 3300uF capacitors store power along with a third 1000uF up front added for balance.

The little bug works... sort of.  It's persnickety about the orientation of motors, weight distribution, side height, amount of indoor light, and so on.  Too much rear weight and it wants to pop a wheelie and fall back on its butt.  Too much front weight and it has trouble dragging the skid around so it just sits there.  Tuning the motor orientation for optimum performance takes patience. Lots and lots of patience

Nevertheless it is strangely fun to tinker with and to watch once it's operating correctly.  I haven't added the obstacle avoidance Solarbotics antennae (spring switches) yet but that should make it all the more interesting.

This photopopper was supposed to be my first robotics project to sort of get my feet wet.  Instead, I dove in head first (or fell in...) building Sparky then Pokey.

Following a naming trend... I'm calling the little guy Spunky.


  1. That's awesome I want to build one!

  2. Thanks! It was fun to do. Poor thing is still in need of repair though. :(

  3. Why so many capacitors? Do you not need just two?

    1. Though I haven't look at this in 3 years, I recall the three electrolytic capacitors are for aesthetics and capacity, the other two ceramics are required by the circuit. There are, at a minimum, only 3 capacitors required. One large electrolytic, and two small capacitors.


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