A Very Low Cost Deaf Alert Device

Although many of my assistance projects on this blog involve the blind, I’ve been keeping alert to other group’s needs. For example, I’ve spent a lot of time planning a sound/light display for the deaf (and not incidentally, for use when I have my headphones on). Sounds flash lights, and so you can know when there is noise around. Handy for parties, handy for the deaf, handy for me when ‘plugged in’.

Anyhoo, I was slowly planning a fancy audio meter with Fourier transforms using an Arduino to create a spectrum display, and perhaps an app as well, when I found a simple on eBay. Using the LM358 chip, it puts a microphone, 10 LED power display and everything you need minus power supply for under $10.

So – program a Fast Fourier Transform on a RISC chip and add DIY hardware, or use a ready made component I just plug in? Tough choice. I

According to the specs, it runs under 100mA and 5v, so I literally hacked a USB cable to provide the power, and hooked it up (use a meter to test for the outer two power wires, and then connect just them up.) USB is supposed to be OK up to 500mA, but just in case, I first plugged it into a cheap and then plugged that into the computer.USB pinout

Now, several months later, I’m finally writing my observations:

  • It’s bright. The green LEDs are easy to see, they are by any means NOT underpowered, and there are 10 of them. It’s very visible – ’nuff said.
  • It’s adjustable. There is a tiny potentiometer on the device for level adjustment, and at the full setting I’m watching the bottom LED flicker as I type. And of course with 10 LEDs, it’s also good for picking up a wide range of quiet to loud sounds.
  • It’s sensitive. If the room is dark, it flashes quite the green lightning storm from any sound, so it does the job very well. It picks up sounds from other rooms and outside, so I suspect it would be fine to use as baby cry alert or fire alarm alert.
  • It’s distracting (but not too much.) I thought a flickering light would be quickly annoying. It wasn’t. There’s something relaxing about having it flicker gently while I type, and of course it does pick up the louder sounds for me and alerts me about the ‘big bangs’.
  • It’s neat. Although you can (and probably should) make a case for it, I preferred to keep the circuits exposed and just did some 3D printed legs to display it with a slight tilt, and to provide strain relief to the USB cable.
  • It’s convenient. Small (about four inches long), it fits well on my desk and doesn’t get in the way. With a long enough cord I can position it near me, or keep it far away (or place it face down to turn it ‘off’.) While it could probably be battery powered, I only need it at my desk, so the USB cable is fine. Of course, if I wanted to make it more portable I could buy a

All in all, a great experiment, and a very low-cost way to try out a sound meter alert. For someone hard of hearing or deaf, it could be a very, very useful tool. Or plug one in at your next party and watch the ambient noise move the meter. Well worth the low cost!

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