Let's Make Robots!

PLUMBERbot Symet

Solar engine drives small dc motor and makes me smile
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This is PLUMBERbot...a BEAM Symet using a simple solar engine. His name derives from the fact that his apron is a teflon tape round and his hat is a plumbing trim surround that you'd find in your bathroom or kitchen. His solar cell captures the light and stores it in his capacitors. When his capacitors fill up, the energy is dumped to the small dc motor. In direct sunlight, this little guy runs continuously as seen in the video. Under less intense light, he'll twitch about when he feels like it.  I included a couple of attachments of solar engine circuit schematics.  Do a web search and you'll find a bunch of secondary research that will get you BEAMINg in no time.

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Seems like you have a lot of experience with these BEAM robots. I'm trying to build a little FLED solar engine right now, and I was having trouble getting the motor to do more than twitch.

I am using the same FLED engine you posted. The caps are two 2200uF electrolytics in parallel. The solar cell will generate just about 3V in bright light. The NPN transistor (Q1 in your diagram) is a pn2222A. The PNP (Q2) is a 2n3906.

I tried lots of values for the resistor, from 2200 to 5100, with only minor changes. I found that partially shielding the flashing LED from ambient light with a piece of unheated shrink wrap helped a bit.

I finally tried to use a different motor. Now it it works fine. I'm looking forward to integrating into one kind of BEAM or another. I'll post it when I do.

I actually wrote most of this comment, decided to try a new motor, and then had to edit to say it worked now. I was originally going to ask for your advice, but I just thought I'd share my experience, in case others were having frustrati- ah, learning challenges too. 


I'm glad to hear you figured this out.  I'm far from an expert.  Like you, I emersed myself into BEAM for a while...constructed some solar rollers, symets and obstacle detection bots using junk bot methods.  The challenge is finding proper values and configurations with all this stuff since BEAM employs components for things not initially intended for these components.  I have always had a bit of difficulty getting the FLED version of the circuit to work properly.  The LED is always a source of frustration for me.  I've always opted for the simple version that utilizes the 1381 as trigger instead of the LED.  My most successful build of a symet used a PN3904 Transistor...PN 3906 Transistor...2.2k Resistor...1381 'C' Trigger...0.1uF capacitor...diode...motor and 3v solar cell.  Then it's just a matter of freeforming the circuit.  Once the circuit is complete...configure them to (4) 1000uF capacitors...along with the motor and solar cell.  Sometimes the value of your capacitors make a big difference too.  Anyway...this is all good stuff.  Thanks for the comment.

Yes he is in his element in direct sun.  However, with less intense light, PLUMBERbot sometimes stops working and emits a high pitched buzz.  If this happens, I usually have to reset his circuit by holding my hand over his head for a few seconds.  Again, this doesn't happen with greater light intensity.  Could be a resistor value issue or maybe a transister related problem.  He is what he is...a bot that works when he wants to.  We love him for who he is.  Thanks for your comment.

Hey,nice little bot...seems that he's happy when the sun shines :)