Bestiary Logo

Image Home

Image BEAM family tree

Image Sitter

Image Squirmer

Image Slider

Image Crawler

Image Jumper

* Roller

** Symet

** Solarroller

** Popper

*** Design

*** Gallery

** Miniball

** Misc.

Image Walker

Image Swimmer

Image Flier

Image Climber


The BEAM Bestiary is a BEAM Reference Library site.

Moving toward a goal in "spurts"

ImagePhotopoppers are essentially just pairs of solar engines mounted together with motors; they seek out bright sources of light through the differential action of the two solar engine motor pairs.

If you build a photopopper, and it doesn't want to work, Wilf Rigter has a very good debug guide here. Meanwhile, here are some debug tips from Dave Hrynkiw of Solarbotics:

Subject:Re: photovore...oh damn
Date:Wed, 10 Feb 1999 01:19:29 -0700
From:Dave Hrynkiw

Lesson 101 on how to check your Photopopper:

Preamble: Before doing ANY of the following, sit down with your soldering iron and re-touch all the solder connections. We find that 90% of the returns to Solarbotics are fixed in under 30 seconds with nothing more than a soldering iron and some solder to fix bad solder joints. DO IT. Don't think "He can't mean _MY_ solder connections". Yup, I do. I have seen poor solder joints on every returned item from somebody who INSISTED that their soldering is perfect. Another thing - do not be quick to blame your problems on a faulty component. I have seen exactly 3 bad transistors _ever_. And NEVER a bad 1381. With that said, let's begin.

Step 1 - Preparation: Didja mount tactile (touch) sensors on it? Remove them. It cuts down on the complexity of the debugging task.

Step 2 - 1381 testing: If it is running in circles (as it most likely is), that indicates one side is obviously dead, or seriously mistuned. Crank your trimpot all one way - do you hear a slight buzzing? No? Crank it the other way. Still no buzzing? That means there's a problem with the circuitry to the 1381. Inspect your power and ground connections to the 1381.

If you hear buzzing, that means the 1381 is trying to trigger, but the solarengine isn't activating. No buzzing = no 1381 action.

Step 2a - 1381 testing, part deux: Run a jumper from the Vcc (positive) of your main cap or solarcell to the middle leg of the suspect 1381. This will effectively bypass all sensory inputs, and FORCE that 1381 to be the one that will trigger, everytime. Does it work now? Check the IR photodiode - may be in backwards. Did you forget to install the cap for the 1381? Is the 1381 itself in backwards?

What, it still doesn't work? Even after checking that there's a positive voltage on the middle pin of the 1381, and ground to the right-side pin (viewed pins down, text/flat side facing you)? Hmm. Must be the solarengine

Step 3 - Solarengine testing: Run a wire from positive and _tap_ the middle leg pad of the 3904. Do this a few times while watching the motor. Does it make the motor spin? That's a good sign. Now notice carefully - does it spin a bit longer after you remove the wire? Good, that means the Solarengine portion of the circuit is working properly. If it only works while you are holding the wire to the middle (base) leg of the 3904, that means the circuit isn't latching, or staying on. Your 3906 should be inspected.

If you have not found your problem by now, start reinspecting your handiwork for obvious flaws like a blob of solder bridging solder pads, or improperly installed components. Did you use glue to install the electronics? Yes, I have seen this. It doesn't work. So don't do it.



Meanwhile, popper circuits are discussed over in the circuits library.

For more information...

Ian Bernstein has pix of his really incredibly small photopopper here.

For folks that want to build a photopopper, there's no shortage of tutorials online. Chiu-Yuan Fang's photopopper tutorial is here. Ian Bernstein has a tutorial here (he labels it a Solarroller, but trust me, it's really a popper). Ian also has a page on the BeamAnt (fairly advanced photopopper) here. "Andy's light-seeking robots" has a pictorial tutorial on a FRED-based popper here, and Ray Diaz has a new one here.

There's also a (German language) photopopper page over on BeamPlanet with nice pictures and video.

Sitemap  *  Search  *  Submit  *  Legalities  * 

Page author: Eric Seale
This page was last updated on

Creative Commons License
This work is licensed under a
Creative Commons License.