BEAM Projects > FRED Photopopper

Finished FRED PhotoPopper

My FRED Photopopper
(not as pretty as Ray's!)

Photopopper Schematic

FRED Photopopper Layout by
Ray Diaz

Circuit used: FRED Photopopper by Ben Hitchcock, layout by Ray Diaz
Construction Notes:
The BEAM definition of a photopopper is a simple two-motor phototropic photovore. It can either run toward light or run away from it using differental firing of the motors, based on the design. Check out Solarbotic's Beastiary entry on Poppers.

July 19, 2008: I started this project with the assembly of the transistor pairs (see layout above). I marked the 2N3906 transistors with whiteout. I then super-glued them face to face. Do the same for the 2N3904s. Next, I super-glued the two pairs together. I have already made one substitution to my parts list. My original solar cell only put out 2.5V in bright light and I will need at least 2.7 for the circuit to operate correctly. I didn't have time to get a photo of my substitute cell, but I will get one out later. The next update will begin with the soldering up of the transistor assembly.

July 21, 2008: As promised, here is a picture of the replacement solar cell. I bought a dozen of these about a year or so ago. They aren't exactly tiny, but they work well. I soldered up the transistor pair assembly then the .22uf capacitor/resistor assemblies. I finished up by attaching the major assemblies together. The next step will be setting up the motor mounts. I will be looking at Ray Diaz's Solderless Motor Mount Tutorial. He integrates the motor mount with the storage capacitor.

July 22, 2008: Well, good news and bad. First, the good: I actually finished putting it together. I also substituted some brass wire for the paperclips and acutally soldered the motor mounts (a lot easier on the hands). Now for the bad: it did not work! After assembling and hooking up the solar cell, the motors would not move. The 3300uf capacitor was charging to 4.3V (under two lamps). I checked all my connections that I could get to, directly tested each motor, and it still would not go. I have probably shorted out one of the transistor leads (it is pretty tight between the leads). So I am am starting over. I have rebuilt the solar engine and will test it on a bread board first before I move to final assembly again. I have attached jumper wires to the new engine to add power and motor connections. I will add more here after completing some tests.

July 25, 2008: I finally figured out what was going on. I had one flashing LED that had a really high resistance, which caused only one engine to fire. After replacing that LED, everything started working correctly! The best way to test a LED is to put it in a black film canister with two tiny holes for the leads. This will ensure a stable dark environment to make your measurements. If you look closely at the motor mount pictures below, you will see little white flags on the motor shafts. This was just to make it easier to see them move. And it also made a buzzing noise so, I didn't have to expressly watch it, other than to make sure the correct motor fired. Once I get the rest of it re-assembled I will replace the last three photos with ones of the actual FRED Photopopper.

July 29, 2008: Finished at last! I used some blue silicon rubber for the motor drive wheels and soldered in the solar cell. In bright light, it is pretty zippy. I really need to source some new solar cells. The style I used here are about all I have left. Let me know what you think. Have fun and try your hand at making one today!

FRED Photopopper parts
Starting collection of parts
Tranistor Pairs
Tranistor pairs, 2N3906 are marked with white out
Tranistor assembly

Transistor pairs assembled

Solar Cell - Front and Back (same cell farther away)

.22uf capacitor and resistors assemblies

Assembled solar engine - Top and Bottom

Motor mount and capacitor

Motor mount and capacitor - bottom

Solar engine with LEDs mounted

FRED - Bottom

FRED - Side
FRED - Front

Finished FRED Photopopper - Front

Finished FRED Photopopper


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