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| Fake Bourns 10 Turn Potentiometer Tested to Failure |
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| samsam11:
I bought the least expensive (under $2) 10K 10 turn potentiometers on AliExpress. Wanting to see how long it would last I rotated it full scale idley for a few months while doing other things, it takes around 5 seconds to turn it 10 times, so with the spec on the real ones being 1,000,000 360 degree rotations it would take 138.8 hours of full time twiddling to get to that, I was not counting but 250,000 or so rotations would not be unreasonable. The failure mode was the wire breaking or the wiper breaking, one may have caused the other and I can't be sure which one came first, a brass colored metallic powder was contained in the lubrication. In my very basic testing at about half way they remained quite linear, but the feel did worsen. They don't hold up to the real ones, but for the price I was not expecting them to, I would not use them on anything that gets daily use or near their 2W power rating. |
| Berni:
If they survive 250k cycles that's still not bad, especially for the price. What is the test jig used to exercise them? |
| exe:
Sorry, I didn't get the results. How many rotations did they survive? How many samples did you try? Did you rotate manually? My experience: I bought several different species from aliexpress, some of them feel fine, but one of them fall apart in my hands (could be fixed with glue, but the shaft was bent too, so I just threw it away). I'd say they are usable for light usage. Since quality varies a lot, I wouldn't use it for a mission-critical system. On the other hand, for a mission-critical system I'd use a DAC or something to control parameters, not a mechanical device :). On my psu I have four of 10-turns pots (two channels, each with CC and CV knobs). So far the most expensive (presumably original Bourns part that I bought for $15-17) feels the best. Rest (including original parts from a different manufacturer, but I don't remember the brand, it cost $11-14) works much worse. Devices from aliexpress are OK. I've been using my power supply for like three years. The usage is relatively light. |
| samsam11:
I did not use a jig, I just turned it while I was doing things that did not need two hands. It has been around 3 months since I got them, and I did a rough estimate based on how long it takes me to spin it 10 turns (around 5 seconds) so in an hour I could do 720 3600 degree rotations, as Bourns rates lifespan by shaft revolutions that is 7200 cycles by the metric Bourns uses. So 250,000 would take 34.7 hours, around 30 minutes a day. This may very well be quite off, but even plus minus 100,000 cycles it gives a reasonable idea of lifespan. This was only tested on one sample, I don't have that much free time. |
| rs20:
Hmm, not sure I trust this reasoning. The rate at which you turn the pot while attentively timing it is possibly very different to the rate when you're multitasking, and who knows how often you took little breaks without realising. Why not write a simple arduino sketch to measure sweeps of the value via the ADC next time? Would've been about 20 lines of code tops and would have removed all doubt. |
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