Wooden Robot Hand Part 3

Here the last part of the robot hand, the program, I hope the robot hand posts have been somewhat interesting to read for you!

These are the different switches mentioned in the code:

Switch 2 = Open Hand

Switch 3 = Fist

Switch 4 = Flippin the bird

Switch 5 = Rock on!

Switch 6 = Pointing

Switch 7 = Thumbs up

Switch 8 = Peace!

Switch 9 = Wrist forward and back

To view the program code, you will need the Arduino software (which can be found at http://arduino.cc/)

Here's a link to download the program.

Robot_Hand.pde

Wooden Robot Hand Part 2

Here's how I went about making the wrist:

I traced out and cut the wrist from some 19mm thick pine (same width as the wrist servo).

In the wrist I cut out a spot for the servo to mount and a large notch in the centre for the wiring. I made the top section a bit narrower so that it will match the width of the palm.

I finished up with a stain and varnish!

I used similar hinges to secure the wrist to the palm. I then mounted the servo to the wrist and made a small arm to stop the hand falling and to enable the wrist to move forward and back.

I originally had trouble with the servo arm. I first tried to attach the arm to the side of the palm, but the servo turned out to be too weak to hold the weight of the hand. So I made a small bracket out of sheet metal to add more leverage to aid the servo.

Below shows the servo, hinge and servo arm.

I next wired up a prototyping circuit board with some switches, resistors and a few leds. The circuit for all of this is shown a bit further down.

A you can see in the photo to the right, I also made a removable base by screwing two pieces of 12mm dowel to the base and then drilling two 13mm holes into the bottom of the wrist. I makes for easy programming and testing. It also looks pretty cool.

Next came mounting the circuit board to the wrist. On top of it I mounted some clear perspex with holes for the switches and leds to poke through. I also mounted two toggle switches onto the perspex, one to isolate the 9V to the Arduino and another to isolate the 9V to the three regulators that supply the servos.

The purpose of the servo isolation switch is to allow me to make changes to the program without the servos moving about.

I finished up the wrist by mounting the Arduino, screwing on the voltage regulators and attaching a battery.

Before I mounted the Arduino, I dressed in the cables from the switches and servos so that they looked nice when they went into the Arduino. I also added a piece of perspex to protect the Arduino.

For the voltage regulators, I used the LM7805. The ones I chose only had a 1A capacity, so to be on the safe side I used three (two servos per regulator). In hindsight, I could have used 10A regulators, but they would have taken longer to obtain and I was impatient!

I mounted them all on a piece of aluminium that can act as a heat sink. The regulators are mounted on the side of the wrist, in between the Arduino and the battery.

The battery is just an ordinary 9V battery with a piece of aluminium holding it in place. I discovered later that a 9V battery doesn't last long when operating the servos constantly. So I would recommend either hard wiring a socket so you can plug in a power supply adapter or just getting a bigger battery.

Here's the circuit I drew up for all of this. At the bottom of the image is the circuit for each of the voltage regulators. I only used one 0.33uF capacitor on the input side since the regulators were paralleled up.

Switch S1 and the green led is for the Arduino supply. S2 and the orange led is for the voltage regulator and servo supply. The red is just an output from the Arduino. The red led lights up when the servos are moving, just to let you know not to press any other buttons.

I will post the Arduino program I used soon.

Wooden Robot Hand Part 1

This is one of my most recent projects: a wooden robot hand.
The fingers are controlled through 5 servos pulling on 2 pieces of fishing line each, one on the front of the finger and another on the back. When the servo moves it releases one side of the finger and tighten those other. I chose this method because at the time, it sounded pretty simple and cheap to achieve.
The drawback to this design is that the fingers are extremely weak and cannot grasp anything. So until I get around to figuring out how to make the fingers curl around tighter, the hand will probably never hold anything.
I have since seen some videos of other servo robot hands that seem to achieve hand strength, but I haven't really looked into how they did it. But in my defence, I think my hand looks more hand-like than the others that I've seen. Also, none of their's "flips the bird"!

The servos are controlled using an Arduino Mega 2560. Obviously my choice of Arduino is a bit of an overkill (since only 14 I/O's are required), but it is all I have available for now. Eventually I'll replace it with an Arduino Uno or Nano. The whole thing is fed from a 9V battery. The servos get their 5V from 3x 1A voltage regulators. I'll get into the wiring and what-not on another day.

So here's a run down of how I made the hand:

I started with tracing out my left hand and marked out the design that I was going use to build the hand itself.
I first measured out and cut the segments to make the fingers and thumb. I used 12mm dowel. I chose to make my own hinges because anything at the hardware store was either too big, too flimsy or simply split the dowel in half when I tried to put screws in! So I ended up making the hinges by cutting up some sheet metal into a two hole mechano-like piece. I used two of these metal pieces for each pivot point with a 1/8" brass screw holding it all together. The small ring hooks are for the fishing line to thread through and tie off at the end of each finger, front and back.

After redrawing several times, I decided upon this design for the palm. It allowed room for the servos to fit and kept the palm pretty strong.
The palm is made up of 2 separate parts that screw together later; the main section which holds all 5 servos and 4 of the fingers (attached with the same sheet metal hinges) and a small section that holds the thumb. The smaller section is angled roughly 45 degrees down.

This is how the palm turned out (thumb piece not built yet!)

After assembling all of the fingers and the two palm pieces, I gave it all a quick once-over with some stain and varnish (just to be fancy).
As you can see in the photo, I then mounted the 5 servos.


I got the 5 servos for AU$30 on eBay. Heaps cheaper than at the hobby shops in Adelaide!

Now the reason I used 12mm ply in the construction of the palm becomes a bit obvious in this photo. I matched the width of the servos to the ply wood width so I could attach some aluminium sheet on both sides of the servos. Two reasons; it prevents the servos from falling out (they weren't screwed in too well) and it looks kinda cool!











I'll continue with the construction of the wrist and the wiring on another day.

My first blog!

So yeah, this is my first post for my first blog. Hullo!

So, this blog will pretty much be about the various small projects I undertake at home in between work and usual home life.
My projects vary from paintings and woodwork, to electronic endeavours.
In between projects I'll post a lot of my previous projects from the past year, along with photos, videos, steps I took, etc.