4 ms·

I guess the point is... say you use a microchip connected to a sensor to determine when to switch off a gas nozzle. It would work, of course, but if the sensor

by umvi 6y ago

I guess the point is... say you use a microchip connected to a sensor to determine when to switch off a gas nozzle. It would work, of course, but if the sensor fails, or there's a bug in the firmware, or if power fails... gas spills everywhere. Whereas if you couple the trigger to a physical phenomenon that doesn't need electricity to work, now there's only one thing that can fail, and that's the part converting the physical phenomenon to a mechanical action. I love computers as much as anyone on this site, but I like mechanical things too. I much prefer mechanical locks to digital ones. Mechanical locks are extremely reliable and well made ones work for centuries. Whereas I wouldn't trust a modern fingerprint padlock at all - what if the sensor fails? What if the batteries run out? What if moisture gets inside and corrodes the circuit board? One of the main jobs of a lock is to open when I need it to, and I just don't trust battery powered locks to do that.

jjk166 6y ago
> now there's only one thing that can fail That's the sticking point. People tend not to think of mechanical systems as systems full of many components any one of which can fail, but they are. In the case of the gas nozzle, you have the orifice for the airflow which can get blocked, you have the diaphragm which can break, you have the connection to the lever which can sever, you have the lever itself which can bind. Critically if it does fail, it fails catastrophically - gas spills everywhere. On the other hand consider a system employing a capacitive level sensor. When the sensor comes into contact with fluid, the dialectric constant changes and thus the voltage drop across the sensor increases to the point the valve will close itself. If anything goes wrong, say you lose power or a wire breaks or someone physically rips the nozzle off, the voltage still decreases below the cutoff threshold so the valve still closes - it fails safe. People like mechanical systems because they are easy to visualize, but that's not the same as being simple or safe. At the same time, most of our experience with electronics is with low cost consumer electronics where the price of failure is low and there is strong financial incentive to use cheap components with short life expectancies in configurations that aren't fail-safe, so we tend to associate electronics with being unreliable. But on a fundamental level, the force stopping two gears from passing through each other is exactly the same as the one producing a current when you apply a voltage to a piece of copper.

by umvi 6y ago

jjk166 6y ago

> now there's only one thing that can fail That's the sticking point. People tend not to think of mechanical systems as systems full of many components any one of which can fail, but they are. In the case of the gas nozzle, you have the orifice for the airflow which can get blocked, you have the diaphragm which can break, you have the connection to the lever which can sever, you have the lever itself which can bind. Critically if it does fail, it fails catastrophically - gas spills everywhere. On the other hand consider a system employing a capacitive level sensor. When the sensor comes into contact with fluid, the dialectric constant changes and thus the voltage drop across the sensor increases to the point the valve will close itself. If anything goes wrong, say you lose power or a wire breaks or someone physically rips the nozzle off, the voltage still decreases below the cutoff threshold so the valve still closes - it fails safe. People like mechanical systems because they are easy to visualize, but that's not the same as being simple or safe. At the same time, most of our experience with electronics is with low cost consumer electronics where the price of failure is low and there is strong financial incentive to use cheap components with short life expectancies in configurations that aren't fail-safe, so we tend to associate electronics with being unreliable. But on a fundamental level, the force stopping two gears from passing through each other is exactly the same as the one producing a current when you apply a voltage to a piece of copper.