The History Of Wallbanging

Why is this robot called Harvey Wallbanger? After the vodka and OJ cocktail? Well, its gait might remind you bit of someone who's had a few ...

The original Harvey Wallbanger competed in the IEEE Micro Mouse contest during the 1980s. It could be switched to use either the left-hand or the right-hand rule for maze solving. It won prizes for both the fastest time and the most improved. Tom developed the BEAM Bicore version presented here, but it's entirely possible that someone else thought of it first. If so, we apologize for not giving due credit.

Figure 8. A two-Nv loop or bicore.

PIC's pull-down resistor, the more noise there is.

As we know, the '240 switches at half of Vcc. If a signal on an inverter's input is close to the switching point, the inverter will switch rapidly high and low. Earlier, this was useful in building robots like the Bare Bones Photovore.

Now, however, this is problematic because the next Nv might twitch a bit when its input switches. If it twitches even a little bit, then the next Nv in the chain will also switch on and off rapidly.

Before you know it, all Nvs on the chain start bouncing on and off and you get a light show. That might be fun, but it's not what you want.

The problem of the twitchy Quadchain can be simplified to one Nv in a chain not becoming inactive when the next becomes active. We can solve this problem by connecting the Nvs using the Trigger input and the Kill input (Figure 7).

The first Nv becomes active, then passes the process to the second Nv. The moment the second Nv switches, it sends a kill input back to the first Nv. Thus, the chain cleanly switches and the process smoothly circulates from one Nv to

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