A few weeks ago I was messing around with some old Nerf guns and after glancing at a near by dart board I thought popped into my head. Could you make a dart board for Nerf and how would you do it. I started thinking of ways to accomplish the task and I remembered the few times Dave from the EEvblog has mentioned piezo vibration sensors. I found one cheap on ebay and a few days later I had two of the suckers.

At about 3$ a pop that's not to bad at all. The plan was to mount each sensor onto a segmented portion of the board. My main concern at this point was if the sensors would pick up a dart impact and if they did could you keep them isolated enough to tell witch segment was hit. I theorised that if I mounted each segment on foam they would be isolated enough. I took a piece of ply wood and some foam and built a quick prototype.

With both sensors attached to my scope I took my strongest Nerf gun and took a shot at nearly point blank.

The one on the top was with the probes in x10 mode and the bottom is x1. x1 is mode essentially places a 1M ohm resistor across the probe leads and it shows a drastically lower voltage. I think I'll do similar for the final application circuit or use a TVS diode. Not sure on how I'm going to limit the voltage yet.

Getting back on track the yellow trace is the sensor I shot and the blue trace is the near by sensor. They are an order of magnitude apart and it should not be difficult to filter out the near by sensors. In other words the project is feasible. The next step is to figure out the exact design of the board and what filter circuitry I will use. At the moment due to the shear number of possible segments I'm looking at a comparator based solution that out puts a 1 when a segment is hit.

It will be nice to work on a more "useful" project for a change. Most of what I've built so far has been trinket type stuff.

Edit: Wth is wrong with the formatting tools. Anyways, fixed.