Freeform Microcore Walker Tutorial
From BEAM Robotics Wiki
Building a MicroCore Walker Step by Step. Send any questions or comments to [[1]].
These pages are copied over from Rays' Beam Site to put them in context and get them finished!
Contents |
[edit] Parts List and Information
74AC14 Hex Schmitt Inverter IC (the MicroCore chip).
74AC240 Octal Buffer / Line Driver with Tri-state Outputs (The Motor Driver).
.22 uF Monolithic Capacitors (Four).
10 uF Monolithic, Electrolytic or Tantalum Capacitors (Two).
2 Meg Resistors red-black-green (Four).
4.2 uF Monolithic or Tantalum Capacitors (One for the Reversing Circuit).
3 Meg Resistors orange-black-green (One for the Reversing Circuit).
SIP Sockets We use these to connect the MicroCore to the Motors, the Batteries and the Feeler(s). (We need Eight of these).
I Highly Recommend buying all your parts from Solarbotics.com and while you're at it you should really get the "Junkbots, Bugbots, and Bots on Wheels" book. -- This book is a must read!
You'll also need the basic tools.
Now we're ready to start building the MicroCore.
[edit] The MicroCore
If you'd like to understand how the MicroCore works, study Andrew Miller's 2-Motor Walker Tutorial. You don't really need to understand how this all works.
You may want to build the Motor Driver first to get used to freeforming and soldering and then tackle the MicroCore. It's easier to de-solder and fix stuff on the Motor Driver than on the MicroCore.
Study the full MicroCore Schematic below so you get an idea of what we're going to do. Don't worry if it seems too complicated because I'm going to fill that schematic in gradually in the order that we're building it.
We'll build the MicroCore in a logical order. That'll make it easy to solder the parts so the first parts you solder are not in the way of the next ones.
I recommend that you follow this procedure and later, find your own personal process if you feel that you can improve it. But I highly recommend that you follow this one for your first MicroCore.
The first step is to prep the 74AC14 IC.
Clip off the THIN part of the IC's "legs":
When you're done, it should look like this:
Tin all the IC's connectors. -- Tinning means to put a bit of solder on a metal part to make it easier to solder another part to it. "Paint" a bit of Flux paste onto the connector, then put a bit of solder on the tip of your Soldering Iron and touch its tip to the connector. You'll see the flux go up in smoke and then you'll have a nice little bead of solder on the connector.
I use this technique for every connection I make... first "paint" some flux on each part, then dab a bit of solder on the tip of my Soldering Iron, then put the two parts together and last, touch the tip of my soldering iron to the parts. -- The solder seems to Jump from the iron's tip to the parts. This makes a very clean connection with a small amount of solder.
The most important tip I can give you is to use very little solder for each connection. Remember that you will solder many different parts to the same connector (one on top of the other) so if you start with a big glob of solder, the next time you solder another part to it, it'll have too much solder and you'll end up soldering bridges where you're not supposed to. So keep it clean and use tiny bits of solder.
Notice the beads of solder on each of the IC's connectors in the image below:
Now we build the Reversing Circuit:
Using the technique described above and a set of Helping Hands, solder a piece of one strand wire to Pin 2. I use Radio Shack's 4 strand, 24-gage, Telephone Wire. It gives me 4 solid wires (Red, Black, Green, Yellow).
Bend the wire over and around the chip and solder it to Pin 13.
This completes the Reversing Circuit.
[edit] The MicroCore's Motor Driver
If you'd like to get an idea of how the Motor Driver works, study the 74*240 Reversible Motor Driver article. You don't really need to understand how this all works. If you follow the instructions and build it correctly, it'll all work at the end. Don't worry if it seems too complicated because I'm going to fill in the schematics (wiring diagram) gradually in the order that we're building it.
Note: We'll be soldering connections and components on both the top and the bottom of the chip, so when you follow these steps, you have to be 100% sure of which way you're looking at the chip before you solder anything. Check twice and compare the schematic and the chip before you solder. -- De-soldering is always harder than soldering, so check twice before you solder and you won't have take things apart to fix them.
Prep the 74AC240 chip as you did the 74AC14.
[edit] Connecting the MicroCore and Motor Driver
The MicroCore by itself doesn't put out enough voltage (enough power) to move the Servo Motors. We need to add a circuit that amplifies the MicroCore's signal, and in our case we'll add reversing capability to the circuit as well. This signal amplifier is called a Motor Driver.
So now we connect the MicroCore with the Motor Driver.
Start by connecting both ground pins together, (Pin 7 of the 74AC14 to Pin 10 of the 74AC240. Then add a SIP Socket to the 74AC240's Pin 10.
[edit] Making the Body
The body of the walker is very easy to build. It's basically made of only four parts: Two Servo Motors and two AA Battery Holders.
This body is so simple that we won't have to go into such detail with these steps.
We're using Solarbotic's GM4 Servo because it comes already modified for full 360 degree rotation, and without the standard servo circuit board.
If you're starting out, I highly recommend that you buy the GM4 Servo. You can learn how to modify a servo yourself by studying "Hacking a Servo".
See Solarbotic's battery holders here. A power switch is optional. It's nice if you have it but if you don't, you can pop a battery in and out of the battery holder to turn it on and off.
The beauty of this design is that the body uses only the parts it needs to function. Nothing is added -- which makes for a very "clean design". You'll see what I mean when we start building it. Which is right now...
First, unscrew the top off of the Servo and switch it 180 degrees so the wire face the opposite way. (Do this with both Servos). They should look like this when you're done:
[edit] Building The Legs
This section is still missing.
[edit] Building The Feelers
This section is still missing, in the meantime refer to Making a Guitar String Touch Sensors.
