Q. Like everyone, I need to build some animatronic parts. Getting scrap acrylic from the hardware store is pretty easy, but I need a good way of cutting it. Right now I'm using a hacksaw with problems getting a clean cut.

I currently have a table saw and Dremel tool. The table saw seems like overkill, and I'm not sure if the acrylic would gunk things up. The Dremel with a cutting blade works okay for very small things, but it's not great. So, that leads me to two thoughts:

* Tabletop band saw. Seems like it would be good for cutting straight lines. Has a miter guide and adjustable table angle for bevels. Seems like it's possible to cut curves, but not as readily as a Scroll saw. Seems like it would be great at curves, but harder to cut a straight line since you don't have a miter guide. Also has adjustable table for bevels.

What would you recommend? I'm leaning toward the band saw at the moment. There may be other options I'm missing, however.

Thanks,
Mike

 A. Spektrum's DX6 RC System with 2.4GHz spread spectrum

HackerSafe: Each Spektrum transmitter has a GUID (Globally Unique Identifier) code. Binding is the process of programming the receiver to recognize the GUID of a single, specific transmitter. Binding teaches the receiver the specific GUID of that transmitter so that the receiver will only listen to the information from its previously bound transmitter and ignores everything else. With over 4.2 billion GUID codes, the chances of having a interference from another transmitter is virtually impossible.

 A. Here is an overview on some parts of the code that are necessary for constructing AC Voltage projects. This information is critical not just for working on controllers but for all household electronics work, from rewiring a lamp to installing an outlet in a room.

Color Codes
The key to wiring AC devices correctly is to follow the color code for wires and terminals. Green wires and wires without insulation are the safety ground and are connected to all metal boxes, conduits, and frames. Their screw terminals are green; sometimes they have green clips instead of screw terminals. Proper installation of green wires minimizes the hazards of electrical shock and fire while reducing electrical noise. The safety ground wires should be the same size as the other colored wires in a circuit. The green line must never be switched, fused, or run through a circuit breaker. It carries current only in the case of a fault in the circuit.

The white wire is the power return. It carries current back from the load, but is close to ground voltage except when a fault occurs. The screw color for the white wire is silver. If all the wires in a cable are the same color (as is the case in plastic lamp cord), the correct wire to use for the power return will always be marked. The mark is usually a series of ridges along the outside of the wire or, more rarely, a colored thread wrapped around the copper conductor. On AC outlets and plugs the white wire goes to the wider. prong (the indication that it is the marked prong). Like the green wire, the white wire is never switched, fused, or run through a circuit breaker.

The power wire can be any color except white or green; it cannot be a bare wire. The most common colors for the power wire are black, red, and blue. The screw terminals are brass colored. Since these wires carry power to the electrical device, they are the only wires you can switch, fuse, or run through a circuit breaker.

Wire Size
The larger the number, the smaller the size of the wire. Even numbers indicate that the wire is copper. Most electronic devices are wired with #12, #14, or #16 wires for AC power. Solid #12 wire is now standard for long runs and for house wiring and is also used for high-current loads like heaters, hot plates, and air conditioners. If you plan to plug several medium-power electronic devices together and run the cord more than 15 feet, you might go to the extra expense of using #12 wire. For most medium-power microcomputer and home electric systems, #14 wire is adequate, and #16 wire will suffice for systems with loads of 100 watts or less. Use multistranded wire for electronic hookup and projects, never solid wire in you projects. Solid wire often fails due to movement, flexing.

Placing wires in screw terminals looks easy, but it is often done incorrectly. To attach a wire to a screw terminal, twist the stranded wire tightly together and form it into a hook. Place the hook around the screw in a clockwise direction. This is important: you will twist the wire more tightly as you tighten the screw if the wire is wound clockwise. If you put the hook on backwards, you will loosen it as you tighten the screw. Close the hook with long-nose pliers and then tighten the screw. When you have finished the wiring, go back over all the screw terminals to be sure they are tight.

Avoid electrical shocks. Follow all codes for AC devices. Unplug the AC cords before opening the case of an electrical or electronic device. Don't work on power equipement while you are alone. Always have another person nearby who can cut off the power or go for help in an emergency. Don't plug any device into live equipment. This rule refers to both connectors and printed circuit boards.

Don't short a computer power supply to ground. Depending on the computer, a short to ground may blow out a fuse, and could conceivably damage the power supply. Check and recheck the +5 wires on all newly-built devices with a multimeter before plugging them in.

A.  How to: Convert between Watts, Amps and Volts.
The formula for finding wattage is very simple.

Watts = Volts x Amps

You have a 1000 watt audio system. connected to a 12 Vdc supply and want to know how many amps is used.

Amps = Watts / Volts

Power Supply is 12 volts: 1000W / 12V = 83.3 Amps.

You have a 30 Amp breaker for a light display. You want to find out how many watts of lights can be used before it blows the breaker.

Watts = Amps x Volts

Since house current is 120 volts: 30A x 120V = 3600 Watts or 3.6 Kilowatts

Lets say a Power Supply puts out 17 amps and 204 watts .
You want to find the voltage.

Volts = Watts / Amps

So 204W / 17A = 12 Volts.

TERMS

Milli Ampere Hour (mAh)
mAh is a term of measurement used in batteries for their energy storage capacity. It is a measure of how much current in milliamps can be delivered from a battery over the period of 1 hour.
Milliamp hours. This is the capacity of a batteries. The larger the number, the longer it will provide power.
mAh (milli-ampere hour) is a capacity rating that measures how much current a battery will discharge over a specified period of time (typically a one hour period). For example a 2000 mAh battery will sustain a 2000 milli-Amp (2 ampere) draw for approximately one hour before dropping to a voltage level that is considered discharged. A 1700 mAh battery will sustain a 1700 milli-Amp (1.7 ampere) draw for approximately one hour. Overall capacity will be influenced by other factors including temperature, depth of discharge and speed of discharge.

Ampere Hour (Ah)
An ampere-hour is a unit of electric charge. One ampere-hour is equal to 3600 coulombs (ampere-seconds), and is the amount of electric charge transferred by a steady current of one ampere for one hour.
Ampere hour is a capacity rating that measures how much current a battery will discharge over a specified period of time (generally a 20 hour period). A 20Ah battery will sustain a 1-amp draw for approximately 20 hours before dropping to a voltage level that is considered discharged. A 40Ah battery will sustain an 8-Amp draw for approximately five hours. Overall capacity will be influenced by other factors including temperature, depth of discharge and speed of charge/discharge.

NiCd - Nickel Cadmium battery. Rechargeable batteries
NiMH - Nickel Metal Hydride battery. Rechargeable batteries

R/C Receiver (Rx) - The radio unit which receives the transmitter signal and sends the control signal to the servos.
R/C Transmitter (Tx) - The hand-held radio controller. This is the unit that sends out the commands that you input.
R/C Servo or Servomotor - Electromechanical device which moves and provides motion to push, spin, turn, pull a linkage set.