On pots and Hall Effect sensors

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Q. Why don't you use Hall Effect sensors instead of potentiometers, aren't they better?

A. This is something we're asked a fair bit via email. In theory a Hall Effect (HE) sensor should be better because it lasts longer - but - in practice it isn't such a clear cut decision. The reason we remain leery of using them is because of their failure mode. Basically, when a pot gets to be a problem it lets you know with increasingly poor centering, or maybe a jittering around neutral. But typically this takes a while because we use premium Nobel million-cycle pots (the best in the business and the genuine Japanese item instead of the clone knock-off). The point being you get plenty of warning. However, with an HE sensor, failure may be sudden - like a light bulb - and if you're flying when it happens . . . oops!

On the flip side, HE sensors are a 'lot' cheaper than our potentiometers and honestly, cheaper is a siren's call in manufacturing. E.g. price is a strong motivator toward everybody in the industry 'wanting' to use them. But let's turn this around and instead ask this; how would you (and modelers in general) view the trade off of 'us' saving 90¢ while increasing 'your' risk of a crash due to the part suddenly failing? This is because HE sensors crap out suddenly instead of slowly going south over time. Note; we're not talking about just the risk of failure, but of 'sudden' failure. I bet you'd take a dim view of it, right? This puts me in mind of my favorite Yogiism . . .



Finally, allow us a bit of salesmanship regarding ProModeler; with other brands if a pot goes south you have to send the servo in for service - you have no choice. Thing is, while replacing a potentiometer is an easy job because there are just three solder joints involved, by the time you get billed a 1/4 hour, plus the price of the part, as well as shipping both ways, the math doesn't work out. End result, you toss the servo. Thing is, because our customers are often not afraid of a soldering iron, you may be interested in knowing we offer parts for our servos. And not just the gears and the case like everybody else - but critically - we're happy to offer you just the potentiometer.


Let me tell you a story; back in the day it was routine to open your servos, remove a couple of small screws and access the inside of the pot. Then, using a cotton swap and alcohol you'd clean the carbon surface and the wiper tip to restore performance to like new. Presto you were good to go another year! Fast forward to today (+40 years) and the pots are sealed. They're also rated at a million cycles (not all, just the best ones like we use). But a million is not forever and thus, pots are actually a wear item. Of course the big guys know it. They could sell you just the pots - but they don't. Maybe it's because they know you'll buy another servo, instead (yes, I'm speculating).

Anyway, in this small way ProModeler is different; we're not run by the beancounters but by the engineers - and - we're modelers. The point being, we actually use our own product (in the trade it's known as eating your own dog food). Thus, you can take it to the bank we 'always' make decisions with respect to reliability, centering, response, and accuracy foremost in mind because we put our own models at risk - just like you. Making decisions like this are what you pay us the big bucks for!

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