Quote:
Originally Posted by PhilBot
In both cases I just had the robot do a few loops and then approach the ramp. The sparks actually occurred at the exposed metal portions of the ramp.
This would be hard to avoid.
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This failure is routinely avoided. But comprehension of some basic concepts such as grounds and impedance are required. If you have only one ground, then this and other events cause failures.
Parts such as interface semiconductors and switches are rated at 15,000 volts and 20,000 volts. But that number only exists when part of a 'system'. For example, a switch connected to 5 volt electronics may be rated for 20,000 amps. But one switch contact would connect to the digital ground or Vcc. Whereas that switch body must connect to a chassis ground - a completely different ground. Another ground might be analog ground. Of course power supplies can have a floating ground. Other grounds may also be necessary. If any ground are electrically connects to another, it must only be at a single point. Only then are each ground electrically different so that transients (such as static electric discharges) cause no problems.
We would do this with computers. Place that computer on a glass table (because other materials such as wood are electrical conductors). Then create static electric charges in a body. Discharge that charge into the computer chassis and keyboard at various locations. If a motherboard digital ground is electrically different from its chassis ground, then a computer does not crash. In fact, where the discharge exists relative to where that current exits a computer to connect to feet (shoes) can help determine where a ground defect exists. Follow the current.
A PCB board typically has a solid copper ground plane. However voltages vary significantly across that copper plane. If a static discharge current enters the chassis, goes up a metal standoff, crosses the PCB board via that copper plane, then returns to the chassis via another standoff; then a crash happens. Current passing across the copper ground plane (a digital ground) causes major voltage differeneces across that copper ground plane. All semiconductors reference ground. Therefore need a constant ground voltage.
These concept are often foreign most techs or electricians. Because it involves concepts only taught to engineers. One key parameter is impedance. Impedance in that sollid copper ground plane is why electronics boards have capacitors all over it. Because normal mode voltages vary significantly across that copper sheet. For same reasons why you are suffering crashed from something so trivial and static electric discharges (a longitudinal current).
Your system apparently has its digital or analog ground connected in multiple locations to the chassis ground. Then specification numbers for interface semiconductors (ie 15,000 volts) are compromised by bad grounding.