Local Control

By "local control", we mean an effect that is either running all the time, senses the presence of visitors and performs for them, or performs at regular timed intervals. It is the opposite of remote control. [We use these terms largely for convenience, so we can divide a large number of topics into smaller subsets. In fact, there are plenty of subjects that cross over the line, germane to both local and remote control.]

Some of the most interesting subjects concerning local control are sensing, timers, and sequencers.

Here is some information on local control...

Sensing
Event Timers
Sequencers

Sensing

In order to automatically operate an effect, you must first determine when you have an audience present. In other words, you must sense them.

The following technologies may be of use:

switch mats - When you step on the mat, it closes an electric circuit. Some mats are capable of switching 110 VAC, others are limited to low voltages. All can be hidden under rugs, mats, and other disguisement.

passive infra-red detectors - This type of person sensor has been popular for automatic floodlights that come on when they detect the body heat of a person in your yard or driveway. We have a project that uses PIR.
break-the-beam sensors - These units are department store classics, sounding a chime when somebody walks in the door and interrupts the light beam. I don't think I've ever been in a Radio Shack that didn't use these. You can also buy them there.
capacitive body sensing - Terror By Design has such a unit, called "T-Sense".

Event Timers

Timers are more important than you think, because they allow you to trigger your effect, run it to completion, and keep it from triggering again until the trick-or-treater has moved on. Nothing ruins an automated scare faster than a kid who has found the switch mat and keeps standing on it, keeping the effect activated, so it can't pop out at the next guest.

The following vendors carry professional-quality event timers:

Haunt Master Products
Cowlacious Designs
Terror By Design
Spooky F/X - rumored to have one
http://www.craigsrobotics.com

Other helpful technologies are:

time-delay relays
solid-state timers, such as the 555 integrated timer chip
- Get the Radio Shack mini "engineer's notebook" on IC timers.
- Prefer the CMOS version of the 555. It has better noise immunity, is more stable, and runs on a wider range of voltages.
- Heavily bypass the power supply - even if running off batteries. Use both a large tantalum (1-10 uF) and small disk (0.01-0.1 uF).
- Don't omit the capacitor from pin 5 of the 555 to ground.
- The 556 chip offers a pair of 555 timers in a single chip.

Sequencers

Sequencers are important for more elaborate effects, such as "when the kid steps on the mat, pop up the giant Jack-in-the-box, wait 2 seconds for him to hit full height, flash the strobe for 5 seconds, turn off the strobe, let Jack drop into his box, and then stay turned off for 30 seconds."

The following technologies may be of use:

cascaded timers - The main timer is triggered by the switch mat and operates Jack; when that timer fires, he then starts another timer for the strobe.

The problem with this approach is that it doesn't scale particularly well - for each additional event of the scare, you must add another timer. This is true even if you are reactivating something that you have already used. So, if you wanted the strobe to flash on Jack a little in the beginning, and then a little more towards the end, you would need two timers just for the strobe.

parallel timers - In this scheme, you trigger two timers at once, but they are set for different time periods, so the strobe stops before Jack drops back down.

This solution has scaling problems similar to the cascaded timers.

commercial multistage timers - These consist of multiple timers in a box, with controls for you to set the delays. The programming tends to be quite simple, like "when the mat switch closes, turn on relay 1, wait X seconds, then turn on relay 2, then wait Y seconds, then turn on relay 3. This is just the thing for our Jack.
Haunt Master Products has one of these.
Since the multistage timer is essentially a set of cascaded timers in a box, it isn't terribly good at repeating a trigger. But it does save money over stringing together several separate timers.
tone decoders - The idea is to use a stereo tape recorder, with one track devoted to the sounds of the prop, and the other track controlling the action. The control track is not piped to the audience, but is fed into a device that does something to the animated prop when it hears the sounds. In the simplest form, this could be a color organ or a VOX. In more complex forms, the control track can contain several different pitched tones, each one activating a different part of the prop. This is a bit complex for a homebrew job. The ultimate tone system uses DTMF, the same tones that are used for "touch-tone" telephone dialing. Due to the popularity of DTMF, simple one-chip circuits have evolved to generate and decode these tones.
Note - In all tone decoder systems, you must take care to keep the tones pure so that they are properly recognized. Many people have gotten good results with tape recorders, but others complain that the tape sometimes runs fast or slow, or stretch over long periods of use, distorting the tones and hurting reliability. Your best bet is to burn an audio CD with the stereo soundtrack - even the cheapest CD player does a faithful job of reproducing sound.
This system scales nicely when it comes to repeating previous actions. If you flashed the strobe earlier, you can flash it again later, just by recording the same trigger tone later in the sound track. No additional hardware is required.
Effective Engineering, "http://www.effecteng.com" makes "M5", for recording and playback of PWM sequences that can be used to drive RC servos and other things.
timing motor and cams - Think of a small electric motor that turns a wheel around once a minute. Now visualize a bump on that wheel, and a switch positioned closely over the rim of the wheel. Once a minute, the bump will pass under the switch, press the switch, turning on part of the scare. Moments later, the rotating wheel will carry the bump away from the switch, and that part of the scare turns off.
This idea is easily extended with additional switches around the rim of the wheel, allowing you to dictate a sequence of on-and-off operations for several parts of the prop.
clicker box - Think of an old-time music box. Inside is a rotating cylinder with little knobs sticking out of it. As the cylinder rotates, the knobs pluck (lift and drop) the tines of a comb-shaped tuning-fork, each tine making a certain pitched note. Some old music boxes use disks instead of cylinders, but work in essentially the same way: protrusions on the rotating member pluck tuned tines, making music.
A similar arrangement is sometimes used for automation, where the rotating drum or disk has attached to it protrusions that activate switches. Traditionally, microswitches are used, which activate with a soft "click" sound, hence the name "clicker box".
This is very similar to the use of a timing motor with cams and switches.
digital sequencer - This solution features a small computer that has memorized a sequence of events. When you trigger the sequence, the computer turns on and off the attached gadgets, in accordance with the program. Since the unit is fairly intelligent, such a device can easily control complicated or lengthy sequence, like the one for Jack. If the behavior of the scare needs to be tuned, you simply give it a new program.
Effective Engineering, "http://www.effecteng.com" makes "Look Alive", a digital sequencer for RC servos.
Gilderfluke, "http://www.gilderfluke.com", sells the Mini-brick 8, a $150 box the size of a pack of cigarettes. The brick is programmed through software run on your PC. After programming, the brick can be disconnected, and runs on its own. 8 outputs, 2 trigger inputs, runs on 9 to 24VDC.
computer sequencer - Since most of us already have computers, why buy another small and stupid one, when your existing computer can do the job? All it takes is some interface hardware and a bit of controlling software.
Craig's Robotics and Animatronics Labs, "http://www.craigsrobotics.com" offers software that controls stuff through a parallel port. The Windows software is $50, DOS $30. You need a hardware interface, which they sell for $100 (4-device) or $200 (8 device). Similar hardware can also be found elsewhere.

Thank you for visiting. Your comments are welcome.
. . . . . .