By Steve Bush 28th September 2023
Omron has an excellent application note on mechanical microswitches, subtitled: ‘Let’s prolong switch life by preventing failures!‘ micro door switch
Hundreds of photos back up information on the causes of failure and techniques for preventing those failures.
It is the sort of detail that makes the heart sing*, in a world dominated by ‘marketing-led’ information-deprived drivel.
*spot the lover of all things electromechanical….
Tagged with: electromechanical product news switch
I browsed the document, and it took me back to the days when I was designing electronics for earthmoving equipment. My customers were the other engineers who used the electronics in their systems, and I spent a lot of time explaining what they should do to minimize failures. This guide to microswitches told me that they spent a lot of time seeing the same failure modes and really wanted to write up their advice and avoid telling each customer individually. I hope it worked better for them than it did for me. 🙂
Good Morning Mr Kurt That is a keen observation. I didn’t think of that document a way of not having to say the same thing over again 🙂 It must have taken ages to prepare – especially finding examples of each failure, or making them happen, to get all of the photos. Seeing it again reminded me of some sub-miniature toggle switches I am having trouble with – I have never had trouble with such things before – maybe there were too cheap. They switch mechanically, but do not always make contact. It might be y fault as they (claim to have) silver contacts, and I am asking them to switch low signal currents. However, in an earlier >100mA <3A application (I bought 10 at once) their contact resistance kept changing. Where are the gold-flash-over-silver versions when a general-purpose stock item is needed!!!!
That was an impressive document, and certainly took a while to put together. I imagine that the photos were obtained gradually over the years, no doubt with plenty of anguish and trauma. That’s usually what is needed to properly motivate (and fund) the creation of such a document. As for the problematic toggle switches you are using.. I suppose the problem could be anything. The contact finish does become important at low currents. I recall recommendations to use gold plated contacts on connectors for that reason. I think the threshold was 10mA or so?? I think Dave Jones did a video where a rotary switch was causing problems due to insufficient spring force, so that’s another way for things to go bad. If you were looking for an excuse to buy the expensive switches, you may have found it. 🙂
Morning Mr Kurt I am glad you like it 🙂 I wonder if a good switch company like Omron has facilities like a sulphur atmosphere test box, and a thoughtful old salt sent a couple of young engineers off with a camera and a bag of switches to learn the ropes by using every tester in the company? Or that qualification testing is so thorough that they produce that set of photos for every switch that makes it to market? On the subject of my switches – they were ‘cheap’ in both senses, but I was not to know that when I bought them… the nuts and threads on them are also pretty awful – I think a better description would be ‘switch-like objects’. I have got away with using silver contacts at low currents for years – not in my former professional life obviously, but for maker purposes. I wonder if good switches have some sort of lubricant which has anti-oxide properties? As a test, I have continued to use a couple of the switch-like objects to control fans, where they will get at least 100mA – time will tell. The replacements for the low current switching (made in China by SCI, I think, with silver contacts and hardly more expensive) seem of far better quality from the outside – they have epoxy seals around the terminals for example. Time will tell here too.
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