Help finding an article in a back issue of Nuts & Vo

[VernGraner]

Hello, I was wondering if anyone could refresh my memory by telling me which issue of Nuts and Volts had an article on building sensors to detect hits on a target from a BB gun? I remember the article but I don't know what issue it was in.<p>I have a project where I need to have a Basic Stamp detect pulses from a sheet of material when it is impacted by a solenoid. (And, before you suggest it, I can't use hall effect devices or sample the circuit, I have to sense the impact).<p>The simplest means I think would be to use a piezo glued to the board and then use some sort of filter to make this readable by the stamp, and rather than re-invent the whell, I was hoping someone could point me to the right issue...? <p>Vern

[chessman]

Several options:<p>1) electret mic wired to comparator. Will give a positive signal when sound level surpasses a given point. Could wire a band-pass filter to respond only to the frequency made by the solenoid hitting the metal.<p>2) pressure sensor (very spendy)<p>3) peizo element as you suggest. when the peizo flexes, it produces a voltage. again, wire it to a comparator to produce a high output when the element is hit.<p>4) use the core of the solenoid as one pole of a circuit, and the piece of sheet metal as the other pole of the circuit. When the two touch, it would close the circuit. This is the easiest way, but also the most sloppy. Not recommended.