Electronics > Projects, Designs, and Technical Stuff
LCSC Bourns Potentiometers
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Pentoad:
The product is a balancer module for lithium cells which uses analogue electronics completely for reliability and cost saving. The potentiometer is compulsory for calibration and to allow the user to set whatever voltage they want. In my tests the setup managed to balance a pack to within 3mv. I can't see any way out of using the trimmers because using fixed resistors would mean that the system couldn't be adjusted or calibrated at all. I heard that multiturn trimmers sometimes just fail or go open circuit after a few years but don't know how much this happens.
GigaJoe:
i bought cheapest ever possible knockoff , around 10 cents, 3296W, haven't had any issue, have couple precision schematics using that cheapo, they run 24x7 couple years ... , but anyway it mean relatively nothing,  one thing that i noticed are torque can be vary a lot,  sometime like malfunction.

is it possible to add a resistor between the wiper and a leg ? 
expensive option: a coded rotary switch with fixed resistors

OwO:

--- Quote from: nctnico on December 21, 2019, 12:37:28 am ---Also if your product becomes too expensive from a 1.5 pound price difference then your margins are too thin to start with.

--- End quote ---
For a product with 4 potentiometers (think buck converter modules with V and I adjust), that's $1.5 x 4 = $6. If the rest of the BOM cost is $10, and assuming a 3x margin, that makes a $30 product almost $50, just for luxury potentiometers. Repeat with all other parts on the board and you may have a non-viable product.

However I do agree with you that you should never skimp on passives and mechanical parts (connectors, etc) because you can't test quality into them. But don't understate the importance of parts cost optimization because by far the biggest cost shavings I've been able to do are parts substitutions. PCBA (BOM lines, number of pads) optimizations don't come anywhere close.
Pentoad:
That's what I have done. I put a high value resistor between one of the legs and ground which will trigger the external alert system and prevent destruction of the customers battery if a pot fails. My next version of the product may use a microcontroller but unlike analog electronics, they can crash and I don't want to risk a battery fire because of that. Also, the atmega 328 only manages 10 bit which isn't precise enough for me.
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