Kevin Roche (kproche) wrote,
Kevin Roche

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Rebuilding ThinBot, Attempt One: Back to the Drawing Board

The Anko pumps are much beefier (over a pound apiece), so I got a new set of panels and set out to rebuild the pump head portion of ThinBot, with blue LEDs behind each pump rotor.

Everything looked great until I tried to assemble the four panels into the head assembly and discovered that the pump motors collided with each other.

Along the way, I figured out a bunch of things for the second attempt, so the effort was not entirely time wasted.

LED with load resistor
LED with load resistor In order to drive an LED properly, you need to provide just the right current and voltage (for this one, about 20 milliamps across 1.5 V). Since my system runs at 12VDC, by putting a properly sized resister in series with it, I can drop the excess voltage and deliver just the right current.
LED with resistor, heat shrink tubing in place
LED with resistor, heat shrink tubing in place after soldering the resistor and wires onto the LED, I need to protect them from shorting to metal parts of the robot. Here you see pieces of red and green shrink tubing slipped over the leads, ready to heat and shrink down.
LED with leads after shrinking tubing.
LED with leads after shrinking tubing. applying a heat gun to the shrink tubing makes it pull in close around the leads and solder joints. I still have to be careful not to flex the LED leads too much, or they will break off, but the wire is flexible; this is why I trim the leads close to the LED and solder the wire leads to them.
Stack of prepared LEDS
Stack of prepared LEDS These are ultrabright blue LEDS, one to go behind each pump on the panel
pump panels ready for component installation.
pump panels ready for component installation. These are the first-try panels for the new pumps; I drilled them out with a milling machine to get the spacing right. You can see the front part of one of the LED mounts inserted into the top panel.
LED in holder on panel (rear view)
LED in holder on panel (rear view) The LED holder snaps in from the front of the panel. The LED pops in from the back, and then a friction ring keeps it in place. Now I can gently bend the LED leads down close to the panel and then route the flexible wires as I need.
LEDS installed on panels
LEDS installed on panels Here are four LEDs installed into two of the panels
LEDS installed in pump panels, front view
LEDS installed in pump panels, front view A closeup, showing what the LEDs look like once they've been fully installed.
Pumps motors installed in panel
Pumps motors installed in panel view from the front of a pair of the Anko pump drives and LEDs installed into a mounting panel. (These panels, which worked for the little aquarium dosing pumps, ultimately proved unworkable and were later discarded)
First-try pump panels
First-try pump panels These were all more-or-less precision machined on a milling machine (because of the bent-edge at the top and bottom, they wouldn't fit into the Rotex punch I would usually use). They also ended up being discarded.
Pump drives and LEDS mounted into first try panels.
Pump drives and LEDS mounted into first try panels. Look great, don't they? Too bad they didn't work.
Rear view of mounted pump drives on first-try panels
Rear view of mounted pump drives on first-try panels You can see the red and black LED wires coming out from behind the gear drive (silver square block). This also shows why these panels had to be discarded. The off-center motor extends too far back, so when two of these were abutted in a square corner, the end of the motor of the left-hand drive ran into the side of the right-hand motor on the adjacent panel. Back to the drawing board. The LEDs, at least, can be salvaged.

As I said, back to the drawing board.
Tags: barbot, barbot 2012, thinbot, thinbot rebuild

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