Nuts and Volts - September 2013

piece of stripboard, but I prefer to use homemade printed circuit boards (PCBs). Since this affair weighs in at a diminutive 1-1/4 by 2-1/2 inches, that undertaking could even be tackled with nothing more than a small bowl of etching solution.

I got the job done (from artwork design to an etched and drilled board) in a couple hours just working with a slapdash system out of my kitchen. Figure 2 shows the PCB artwork I used, while the parts placement guide appears in Figure 3. Figure 4 is a photograph of how my unit ended up.

Here are a few notes of interest to guide you along.

As mentioned earlier, I went with a soldered-in microphone; you’ll spot it in the upper right-hand corner. Next to it is a thumbwheel type trimmer potentiometer (R6). Any type of pot is useable here, though. If you’d prefer to build the thing in a small box with a panel mount control, go for it.

I wanted to be able to use the Sonic Sensor on a breadboard and so utilized pins for ground, +5V, and output spaced in increments of 0.100 inches. I even went one step further and spread them out every other pin so the device would fit into the multiples of the DIY PIC Trainer I wrote about in the February 2013 issue of Nuts & Volts

(pp. 32-37). You’ll see it installed on the Trainer in Figure 5. A plug-in module sure makes life sweet for some rapid deployment of ideas!

Using the Sonic Sensor

I suppose you could connect the Sonic Sensor directly to a driver transistor and relay to simply switch some apparatus on as long as a sound is present. That doesn’t sound all that useful to me, though, since latching is probably what you want.

A better idea would be to use it to fire a 555 timer acting as monostable. When a burst of sound comes in, the timer goes on for a specified interval and then shuts off again. If you’re going this route, remember that the 555 responds to a negative-going edge, so you’ll probably want to differentiate and invert the output gate with, say, a simple transistor affair.

So, maybe you’d like to count handclaps or other sounds. That’s easy to do. Just hook up the Sonic Sensor to some sort of CMOS counter like the 4017, 4024, 4026, 4511, or countless (groan …) other such devices available. You could light a 10-element LED bar graph or perhaps a seven-segment LED display to show the number of bursts detected.

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All fixed resistors are 1/4 watt, 5% values.

Resistors R1 1K R2 4.7K R3–R5 10K R6 10K trimmer R7 100K R8 220K R9 470K Capacitors are 10V or better.

C1 0.001 µF mylar C2–C4 0.047 µF mylar C5 1 µF electrolytic C6 10 µF electrolytic Semiconductors D1, D2 1N4148 diode Q1–Q4 2N3904 NPN transistor Other components MIC1 Electret microphone Miscellaneous: Circuit board, solder, wire, header pins, optional jack, etc.