Incorporating a Digital Sound Recorder into your Halloween Projects


by Scary Terry



Update 6/2010: I recently received an email question about ChipCorders and it made me realize I haven't updated this page with current info for several years. ChipCorders are now made by Nuvoton and you can find more info here. I haven't done any new work with ChipCorders in several years, I now prefer MP3 players for their audio quality and capacity, although I've still got a few ChipCorders in my props. The ISD 2500 series of ChipCorders that I show on these pages have been discontinued and are no longer available. I'll leave the information up for reference, but you can consider it obsolete. There are lots of new choices in ChipCorders at the above link, I've only briefly played with the 1700 series several years ago so I don't have any recommendations as to the best way to go. Hopefully there's enough info on their website to get you started. Note that most, if not all, require a microcontroller interface.

The MP3 players that I'm currently using are the MP3 Trigger V2 from SparkFun and the ÁMP3 player from Rogue Robotics. The MP3 Trigger is about half the cost of the ÁMP3 player and I feel it works just as well.

Ok, on to the info on the ChipCorders, remember this is obsolete stuff:

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.

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).




Product #

Max Time (sec)

Sampling Rate (kHz)













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 an explanation of sampling rate.

You can see that the sampling rate decreases as time increases, so there's a tradeoff 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.



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