Robotic Plant 4 – Followup (Gallery)


Well, it looks like the deadline has been extended, so I have another chance to finish.

To see if more power and different MOSFET would help, I got the only other PTH MOSFET I have on hand, a much beefier FQPF13N06L, and a 4xAA battery pack.   In initial testing, it looked like it will have more than enough power to extend the stem and then turn itself off, so I went ahead and replaced the 2N7000 on the board.  In order to make it stop when the stem was fully extended, I put a jumper in the power line to the motor, attaching a string between the jumper and the end of the stem, which would pull it out when the stem had been extended the right amount.  With the jumper removed, the power to the motor would be interrupted, and the stem would stop, held in position by the friction of the large gear (which cannot drive with a worm in reverse like this.  It worked well, and I demonstrated it at my family’s Christmas gathering, and if I can get a copy of the video, I’ll post it. In the meantime, here are the photos.

I made a new blossom, with some colored paper and paperclips, and so forth.  When I attempted to get video evidence of the final plant in action, however, something had gotten in the way of the gears inside the plant when I re-assembled it.  When the voltage detector went off, the mechanism sprang into action, but the jumper was not pulled free, and when the stem had become jammed at the top, the worm gear ended up stripping a few teeth off of the large gear.  This rendered the mechanism unusable, until I can replace that gear.  If my cousins can get me the video, I’ll post what I have.

This is the schematic for the final version.  Note that with no actual load on the supercapacitors, there will be nothing to discharge them below the threshold of the voltage detector, and therefore, the detector will remain on until self discharge (if it is greater than the charging rate) brings it down.  I had to manually drain the caps with a 500 ohm resistor in testing.  It would have been nice to put a 555-driven blinking LED circuit or something that would eventually take the voltage down, and run periodically, even after the bloom had been extended.

Here is the plant, with blossom, and stem retracted.

Here’s a simulation of the plant with stem extended and blooming.  As I mentioned above, I stripped the gear during an attempt to collect video evidence, so until I can replace it, the mechanism is kaput.

Here’s one shot of the jumper used to turn the motor off when the stem is extended.

Here you can see, from the left, the terminal for the battery pack connection, the terminal for the motor connection, and the terminal for the jumper circuit breaker connection.  In the middle, large and in black, is the upgraded MOSFET, and to the right of that, the original circuit.

Here you can see the battery pack mounting beneath the frame, and the string attached to the jumper.

The gear was stripped off during an attempt to collect video evidence.

Here’s the final perfboard layout, from the bottom.  I had to cover all exposed parts of the circuit with electrical tape, because of all the conductors jammed into the pot together, I was afraid the capacitors would be discharged accidentally, and something fried.

A poor shot of the circuit, from the other side.

This entry was posted in Make It Last, Photo Gallery, Robotic Plant. Bookmark the permalink.

5 Responses to Robotic Plant 4 – Followup (Gallery)

  1. Pingback: Robotic Plant 3 – Final Report | blogsville

  2. Pingback: Robotic Plant 0 – Introduction | blogsville

  3. Pingback: Robotic Plant 1 – Solar Engine Design | blogsville

  4. Pingback: Robotic Plant 2 – Gallery | blogsville

  5. Pingback: Robotic Plant 5 – Really Final Report | blogsville

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