Reducing ESD* at the MTI
In order to provide the best competitive environment the MTI field tiles will be pre-treated with Tech-Spray Anti Stat 1726QT. It is used industrially and in other robot competitions. The MTI crew will carefully follow the manufactures' specifications to avoid any tacky residue on the tiles caused by over spraying. Tech-Spray recommends applying their product at the most once every 30 days for daily use in an industrial environment.
Antistatic sprays work by leaving a residual film on a surface that is slightly conductive. Even slight increases in surface conductivity greatly reduce static build-up. This film is transparent and does not affect the robot’s interaction with the field surface when properly applied.
*ESD is Electric Static Discharge which can wreak havoc with a robot's electronics.
It is important to note that charging of a robot is not usually the cause of electrical disruptions, rather it is the sudden discharge. Discharges can occur when the robot makes contact with another conductor such as another robot or the field perimeter.
When a discharge occurs (a tiny version of lightning), the voltage of the robot suddenly drops (or increases if the robot was negatively charged). This causes current and voltage spikes to flow throughout the robot. The voltages can be large enough (thousands of volts) to inductively (requires no physical contact between electrical conductors or insulators) or physically couple into robot electronics. For example, a large positive voltage can be induced on the ground wires in the robot, effectively (momentarily) reversing polarity on the electronics. In short, nasty things happen. Likewise, electronics that are in the electrical path of the discharge can carry/experience large current and/or voltages.
Special Note on “Closing the Circuit” for Static Build-up:
One if the barriers to understanding how static build-up affects electronics is associated with the basic concept of closing electrical circuits. To get current to flow in a circuit, the circuit must be “closed loop”. Electrons need to the ability to return to ground, whether it is earth ground or battery ground.
This is true of all electrical circuits; however, the way a circuit closes in the case of static build up is not apparent. In the case of static, the circuit does in fact close, but over a much longer period of time than is found in common circuits. An example:
At the start of an FTC match:
- The field mats, Robot A, Robot B and the field perimeter are all at the same voltage (potential). The field is placed on a concrete floor.
- As the match progresses Robot A triboelectrically picks up electrons from the field mat. The field mat’s intimate contact with Earth ground via the concrete, allow relatively easy sourcing or sinking of electrons. The voltage on Robot A starts charging negatively as electrons are removed from the mat and accumulated on the robot. The mat, in turn may charge slightly positively or not at all due to its intimate contact with ground. The robot stores these electrons much like a capacitor stores electrons.
- At some time during the match, Robot A contacts the field perimeter. Since Robot A is at a significantly different voltage potential, an ESD occurs. This discharge transfers electrons from Robot A to the field perimeter.
- These electrons from the field perimeter bleed back to the mat and/or the concrete (earth ground).
- The circuit closes. Electrons flow from Earth to concrete, to mat, to robot (triboelectrically), to field perimeter, back to concrete, back to Earth. The robot stored the electrons for a while until the discharge occurred and the electrons were released.