We solve this problem by using a relay (an electrically operated switch) to accept the 110 VAC line current, and flip a low-voltage switch for us.

WARNING: This project uses line voltage, and is hazardous. If you are not qualified to work on projects like this, please do not attempt it. Get help from somebody who is qualified.

• Background
• Solution
• Parts
• Assembly
• It's so simple. Is it really useful?

• A relay provides isolation from one electrical circuit to another.
• A small coil voltage can control a large load. This is usually how computers control the outside world.
• A high control voltage can control a low load.

This is similar to our trigger relay and Gemmy fogger control.

The relay used in this project is from Hosfelt Electronics. It features a 110 VAC coil and SPDT contacts rated at 16 Amps at 380 VAC. It sells for $.99 (October 2002).

This image shows how our real relay corresponds to the schematic diagram symbol for a relay.

In the picture on the left:

• The coil is attached to the bottom two lugs.
• The lug in the center of the picture is "common".
• The topmost lug is "normally closed".
• The one below it is "normally open".

Our shopping list looked like this (October 2002):

quantity	part	cost	source
1	project box	$1.99	JAL-3 Hosfelt Electronics
1	3-terminal feed-through barrier block	$.35	74-549 Hosfelt Electronics
1	power cord	$.75	AN-10 Hosfelt Electronics
1	110 VAC relay	$.99	45-489 Hosfelt Electronics
1	power indicator	$.75	IND-100 All Electronics

The power indicator is optional, but I like putting it in. It lets me know when the relay is active and something should be happening.

Assembly

Wiring is simple...

SPDT relay contacts go to the barrier strip on the right.

Power input on the left goes to relay coil and indicator lamp.

The location where the power cord exits the box should provide "strain relief", so that accidently pulling on the cord doesn't harm the internal wiring.

In this example, a copious quantity of hot-melt glue inside and outside the box provides strain relief.

The schematic is simple: The power cord goes across the relay coil terminals, as does the power indicator (which consists of a neon lamp and resistor in a single package). The relay's switch terminals go to the barrier block, where they can be attached to props.

This is Digga Dog, a garden decoration we found at Wal-Mart in summer of 2003.

It's the back part of a dog. You put it in your garden, and he makes dog sounds and seems to be digging in the garden.

Obviously, we put Digga Dog in our graveyard, digging up bones.

Digga Dog is equipped with a light-based motion sensor so that he performs when somebody comes near. But he also has a demonstration mode so that potential buyers can see what he does in the store. This is activated by a small push-button.

In the display box, the yellow "try me" button goes to a plug that is inserted into the dog. When you buy the novelty, you are supposed to unplug the demo button and throw it away with the box.

To make Digga Dog perform on remote command, all you need do is take the "try me" cable, cut off the push-button. and connect the wire to the output of the line voltage switch. [Digga Dog is now activated by plugging in the AC cord of the relay.] Finally, plug the line voltage switch input into an X-10 module. Instant remote-controlled prop!

See Digga Dog in action (2.5 meg).

This trick is not limited to Digga Dog. You can do it with any animated toy that has a "push to test" or "try me" function or any device that is operated via a switch, such as a fog machine.

This singing frog is another garden decoration we found at Wal-Mart [summer of 2004].

Dennis likes the line voltage switch so much, he built four of them.

Thank you for visiting. Your comments are welcome.
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