Electronics are funny!


Today after thinking it a while I have decided not to talk about the ISAAC project, but about some funny we found together. Few days ago Victoria and Johan started an intensive testing campaign with the IR source and during a break, and idea come up, electronics are funny!
Everything started long time ago, chatting about everything in which the mechanical members started to talk about how much funny are the stress tests in which a mechanical device or structure is forced over its limits and it breaks down. However, we, the electronics guys, haven’t any visual experiment like that, have we? Of course we have!, and we started to think about them. The first idea was the scheduled batteries vacuum test, but we didn’t want them to explode, we want to use them in our FFUs… So is there something else that we can make to explode? Again the answer is yes, there is! Maybe play with our batteries is not a good idea but, something smaller, like a capacitor? if it is big enough it can store a lot of power and drive it also really fast, am I hearing “short-circuit”? Also big capacitors (a high capacity) used to be electrolytic capacitors, that means that they have polarity, so, if you connect one of them in reverse, what will happen? Let’s see.

Now there are two experiments with capacitors in the air, first charge them and force their discharge by short-circuiting them. The second is just blow up it, by charging it in reverse. The first experiment will produce a brilliant spark, the bigger is the capacitor the most brilliant will be the spark. For the second one, my experience strongly recommend use low capacity electrolytic capacitors, around 10uF since the liquid inside of them doesn’t smells really well after blow it up (Tip: do it in a well venting room). And for exploding them, there are some different ways like connect in reverse and start to increase the power voltage gradually or just set the power source to the highest voltage and current limitation and connect then the capacitor. Each way has a different behaviour! However, remember there is something exploding there, is just a small explosion, but be aware, cover the capacitor with a transparent case before doing….

However, few days ago we hadn’t a venting room ready for the test since we were looking for darkness, and we hadn’t free capacitors neither. Then, how could we make funny experiments? Okay, after thinking a little bit a new idea come up, a new idea like a light bulb, more exactly like the filament… We had a high voltage and high current (over 8A) power source, so, why shouldn’t we try to make a light bulb? This experiment is really easy, you just need a lead and the power source. The lead is mainly build in graphite which is a really good electricity conductor and is really thin, less than 1mm diameter. So, if you force 8A through it, it will dissipate a lot of power, and the only way it has for doing it is in infrared light, and that means hot! That means that during the process you will see it turn from black to red and then to white, a really brilliant white….. The problem is that after some seconds, the lead will break down, but I let you discover by testing how.

Now, moving the text into a more serious area, why is interesting to perform those experiments? it seems they only look for destroying something just for doing it. Okay, I agree, it seems that, but now, let me explain you how can you use that in your future electronics designs and assembling. In the first experiment we have seen what happens when a charged capacitor is short-circuit, it can be even get soldered into another piece of metal if it is big enough. Now imagine that you have one in your board and after switching it off it hasn’t a proper discharging path, and something short-circuit it… That something can be a piece of metal, or even your hand! In the second experiment, okay, a capacitor exploded, now, think that it happens in your board… It’s not nice, and is really easy when you are working under pressure put it in reverse, so, check and double-check after placing them. In the third experiment, a lead have burned out just with current, and it took a lot of current during several seconds, too much seconds for electronics! Now imagine that that lead is one of your components, maybe a resistor?, in your board, and something is wrong and it burns out, have been only that component affected? I don’t think so. Here the conclusion is that using a current limitation in the power source can help you, if you have set it properly nothing will burn and if you pay attention on it, you can turn it off fast enough to save the full circuit….

I hope that you have enjoyed with those experiments and before performing them, please, be sure that someone with electronics experience is controlling them, just for security… And feel free to post new experiments or ideas for them!


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