Quote:
Originally Posted by Al Skierkiewicz
Daniel,
OK, we disagree. What I was alluding to as apples and oranges was your discussion on "wattage". Your discussion on conservation of energy is true if you remember the efficiency of the conversion is not 100%. A 100kV power line at 1 amp is 100kW. At the output of a 100kV to 100 V transformer, the current would be therefore 1000 amps less conversion losses.
The sensitivity of the human body and electronics is more concerned with voltage and available current. Although the main battery is capable of welding wire it is the current (400-600 amps in the robot battery) which is performing that action. At 12 volts, the human body does not produce enough conductance to make damaging current flow. What I am concerned with is the 680 volt output of the inverter (not transformer although one is used in the inverter circuit). According to specifications, the inverter will put out 680 volts loaded with two tubes at 5 ma. (The output current is limited by the series resistance of the secondary winding on the transformer) In reality when the tube(s) is broken, the open circuit voltage is likely much higher, say 1000 to 1200 volts. The internal design of the inverter circuit will not reflect a high current to the input 12 volt source so it would likely never trip the breaker. The internal impedance of the inverter might cause it to burn up before a 20 amp breaker would even get close to tripping on the primary. (remember that the nature of the breakers will reguire sustained currents greater than 166% of rating for several minutes before they would trip.) Either way, 680 volts (or higher) is a voltage that is very uncomfortable to say the least. It's effect on humans, pacemakers, or robot controllers remains to be seen but I think I can predict that the humans will survive but be very vocal while the the effect on pacemakers is not something I wish to test at a First event. The effect on the RC is predictably certain death as capacitors, integrated circuits, and board traces would be subjected to voltages much higher than their design.
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I guess we are just going to have to agree to disagree
I would not disallow a cold cathode lamp. I would inspect it very closely to ensure that it cannot get damaged during a match, and if it was damaged it would be contained within the robot and safely shielded from any conductive surface. I would also do this for the battery, which I consider more of a danger considering that it is not (and cannot be) fuse or breaker protected.
TBH, First does a rather poor job of electronics safety on the robot. A cold cathode lamp should be fused (or non-resetable breaker,not a resetable breaker) with a 2 amp 12 volt (24 watt) or under fuse. The fact that any custom electronics must use at least a 20 amp resetable breaker (even if it's just driving an LED) leaves too much chance for injury. They should open up the requirements for electrical safety and require the teams to specifically state why they used each specific breaker.
Again, teams should design in safety and be able to explain the 'safety' features of their robot, not be dictated a 'one size fits all' answer.
Quote:
Originally Posted by Al Skierkiewicz
Now on to the bright source and CCD pickups. Remember that the CCD produces an output voltage dependent on the light falling on the surface of the device. There is a point at which the light is so bright that the individual pickups are overloaded. As with any device, there is not an infinite dynamic range. There is a point at which too much light causes there to be an excess of photon to electron conversion. As the light continues (and the excess of electrons) a variety of problems occur. The light is transmitted through the layers to other pickup areas of the device and the temperature rises. (Please keep in mind that the energy density of an object is magnified by keeping the smae energy but presenting it to a much smaller area. Ant vs. magnifying lens) The transmitted light cuses errors in the other "pixels" and the localized heating causes additional electrons to be formed. Sort of a dominoe effect. Eventually the heating will cause adjacent "pixels" to saturate and if sustained, this can cause permanent damage to the device. Even after the light source is removed, there will be excess electrons for a period of time.
Small highlights do not cause the AGC to react so small, super bright objects, are not corrected by the AGC and the effect is that the output video will also be saturated or "clipped" at the maximum allowable output voltage determined by the designer. It is also important to point out that AGC does not act on pixels independently but rather the entire output signal. Should the light source cause sufficient disturbance that the AGC circuits react, the effect is to change the gain of the entire output signal, possibly causing the intended green object to be pushed into the black. What you would see looking at a monitor, is a bright white spot surrounded by black.
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What you are saying is absolutely true, but there are 2 things that you are missing.
1> The 'super bright' LED averages around 2000-3000mcd in it's wavelength. At a distance beyond 6" (due to exponential energy loss for didtance) this does not have the luminecence to saturate most CCD arrays.
2> CCD color cameras (like the CMU camera) have 3 CCD elements per pixel. Each element is for 1 of the primary (Red, Green, Blue) color bands of light. Since the target lamp is fairly close to (#00FF00) process green, as long as you avoid LEDs that emit a large portion of their energy in that wavelength you should not affect the Camera. Red (628 nm) and Blue (472 nm) LEDs are good, while White (broad spectrum) and Green (525 nm) would be bad.
I know that Checkmate used LEDs on their robot last year with no interference with other robots.
Note to all who would put an LED on their robot: Be prepared to prove that the vision system will not be affected by the LED.
