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Showing posts from November, 2017

mac -> arduino -> pi -> perfboard -> regulators -> servos

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This is a continuation of the small electronics / microcontroller project mentioned earlier in

http://evandaprojects.blogspot.com/2017/11/robot-claw-prototype.htmlhttp://evandaprojects.blogspot.com/2017/11/first-pi-project.htmlhttp://evandaprojects.blogspot.com/2017/11/pi-prj-1-update-1.html But I've shifted gears and instead of a gantry-like ASRS, I was thinking of trying to make a robot arm.
Structure As usual, I will use a lot of what i have on-hand, and so instead of fancy aluminum t-channel structural members, I'll use 2x4s that I'll rip into thin slabs.
I figured it'd need to rotate.  I didn't have any lazy susan bearings, so i stuck some casters on a board.  It could be smoother. Arms will get mounted to it using pieces of melamine (left over from the concrete casting) 

and bolts (reclaimed from a bench swing that got crushed by a fallen tree).

I made sprockets or gears - we'll see how i use them - with timing belt and plywood cut with a holesaw:

these go…

the hearth wants what it wants

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(see also http://evandaprojects.blogspot.com/2017/11/fireplace-surround-rock-to-cedar.html )
The Plan:
Initially I'd thought we'd buy a big slab of granite or stone and get it cut to shape for the hearth.

The wife didn't see any she liked, or weren't cost-effective, and so suggested we try pouring a concrete one.

Redesign:
In building the form we decided to rethink the design for aesthetic reasons.  Instead of solid beams on the side going floor to ceiling, we decided the wood structure should sit on top of the hearth.  Unfortunately those sides are the main load-bearing elements of the whole thing, and now i need to cut them out.

Approach:
I figured if we poured the hearth, it could certainly support the wooden structure above, but I'd need something to hold it up temporarily while we cut out the supports and poured the concrete beneath it.  I removed some cedar and attached a 2x4 spanning the width, and held it up with jack stands on either side.  Then cut away the …

airboat

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I built an Airboat with normal RC components -- I'd never done anything with RC before.
The chassis was made from the wooden pieces of my child's broken catapult model. The rear floats are 1L bottles, the front is another bottle (whose cap was lost, so covered with cling wrap).
The electronics are a 7v NiMH battery powering a speed controller which in turn powers the RC receiver and the motor.  The receiver then controls and powers a servo.
The servo controls a rudder (a pcmcia placeholder card!), the main motor turns a 10" propellor.

Initially i wanted the fan at the back, but I wasn't sure how to make it high enough to avoid hitting the water but still not push the front end of the boat downward.  Eventually i put it on the front of the boat where it was much less of a problem.
The entire thing is held together with tons and tons of hot glue.
The good: I was really surprised at how well the rudder worked.the 7v battery never ran out for at least 20 minutes

The bad: I…

pi prj 1 - update 1

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Spent another hour(ish) last night:

Refining the old:

screwed the motor to the 2x4 and put a belt on it and an idler pulley.connected the ends of the timing belt with masking tape and wrapped it with some stiff wire -- just like the pros.

Something new: 

Added a bump switch to the pi setup (which apparently requires a couple resistors too)Added some code to read the switch and reverse the belt.Put the code (99% of which is taken from the internet) on github.

The idea is that eventually the bump switch will be activated by whatever carriage i have mounted on the belt, so the system will know the limit of the belt's range.  I'd need one on each side.

first pi project

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Plan Pursuant to my aforementioned automated storage/retrieval project, I'd ordered a bunch of hardware.  I've played with Arduino before, and this time i wanted to try a raspberry pi.
Equipment I ordered: * raspberry pi, model 3b -- $30 for a pretty full-featured computer! * a microSD card, since the pi needs it. * a pi "cobbler+" (which lets me easily use the pi's pins on a breadboard and, more importantly, labels them) * a pack of 5 steppers, each with a small driver board (more on these later) * some timing belt and pulleys
I had: * various power supplies, and a voltage converter/regulator * breadboard * wires and jumpers and alligators * a battery bank (because the pi needs more juice (2+ amps!) than any of my micro USBs supply)
Setup
An old ATX computer power supply supplies 12v to a buck converter/regulator that sends 7.3v to the motor driver. The battery bank supplies 5v at 2A to the pi, which (via the cobbler and breadboard and some jumpers) sends control …

robot claw prototype

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I've been thinking about building a miniature single-aisle (2d) ASRS, like this:

But simpler, and smaller.  Luckily, DIY CNC and 3d printing is fairly common now and I think i can use a lot of parts from those -- just tipped vertically.

One tricky difference is that instead of a cutting or printing head, I'll need a little grabber claw and I want to minimize the wiring, weight, and complexity -- i was hoping to get away with just one motor rather than something to extend/retract an arm and another thing to pinch/release.

That is: I want something that can reach out, grab something on a shelf, and pull back while holding it.  Then i want to be able to reverse it to put things on the shelf from the claw.

There are a million awesome linkages in the world, but i find them very hard to think about.
https://makezine.com/2015/04/20/understand-1700-mechanical-linkages-helpful-animations/
http://507movements.com/index02.html

I guess the one i hit on accidentally was sort of similar to…

fireplace surround - rock to cedar

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Plan: remove old rocks, replace with wood, hide some wires behind for tv & stereo.