This is a "how-to" on incorporating a digital sound recorder, specifically an ISD 2500 series ChipCorder from Winbond electronics, into your Halloween projects. My goal in writing this is to keep it VERY SIMPLE. I will leave out any unnecessarily technical information and make it as basic as possible.

Update 8/2007: The ChipCorder manufacturer (Winbond) has discontinued the ISD 2500 series. It appears that an improved replacement is their 1700 series (higher sampling rate, longer record time). I have very little experience so far with the 1700 series (my last few projects have used uMP3* players which have superior audio quality and nearly unlimited playback time......at a MUCH higher cost than ChipCorders) but I hope to have an update soon. The 1700 series is NOT a direct replacement for the 2500 series as the command structure is entirely different. The 2500 series is still available from a few suppliers including Jameco, more info on page 2. (*Click here for more info on the uMP3 player).

For those of you who don't want to build the boards I'm describing below, I've included a list of kits and ready made units at the end of this article.

What is a digital sound recorder? It's a little electronic chip about the size of miniature Hershey bar. The ones we'll deal with here store up to 120 seconds of sound. The quality of sound is what I describe as "telephone" quality. It's OK for most sound effects and voice, and acceptable for music (think telephone). There's a link for some sample sounds below. If you want really high quality sound, this is NOT the way to go.

Here are the "rules" around which this piece is written:

• It's based on the ISD 2500 series of ChipCorders. They make other series, but the 2500 is user friendly, reasonably priced and has substantial capacity. More on selection of individual models later.
• There is some soldering necessary in putting together these circuits, there's no way around it. Either you need these skills or maybe have a friend who can do it for you. The circuits I'll present use a minimum of components and are not complicated.
• To record onto the ChipCorder, you'll transfer directly from your computer to the ChipCorder. This means you'll need to know how to record and save sounds on your computer. You'll also need a cable to connect between your computer and the ChipCorder circuit, more on that later.
• The circuits I show will work correctly as long as the entire recording time is not used. This simply means that on a 2560 for example, you can record up to 59 seconds of sound. If you want to use the full 60 seconds, you'll need a reset switch (see note on advanced recorder page for more details).
• To play back sounds, we'll use computer speakers (or other amplified speakers). The ChipCorder can drive a speaker directly, but it's not very loud and is unsuitable for most haunt situations.
• We'll trigger the sound playback in two ways, either through a switch or a continuous loop.
• The circuits are powered by batteries or other simple power sources.
• Can you vary from these "rules"? Absolutely, but we've got to start somewhere and this is my way of keeping this as simple as possible.

Selecting a ChipCorder. Since we're limiting our selection to the ISD 2500 series, there are only two factors we need to consider, time and quality. Here's a chart showing the ISD 2500 line up. We'll address the "sampling rate" column in just a moment. (Note: there are some older 2500 models still available, the 2532, 2540, 2548 and 2564, but the ones on the chart are the latest in the 2500 series).

Sampling rate is how often the electronics inside the chip look at the sound and send them to the output. The higher the number, the better the sound quality. (Here's a good, brief explanation of sampling rate).

You can see that the sampling rate decreases as time increases, so there's a trade off between the two factors.

The Max Time is the maximum amount of sounds the chip will hold. There is no minimum, so a one second sound will play and the chip will be ready to play again after one second.