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Guest HepburnUGA

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Guest HepburnUGA

Well, I just finished my first throttle prototype, and I must admit...it's absolutely horrible :) My main complaint is with the pots. I bought some el-cheapo Radio Shack pots and they stink. I get all sorts of interference (I used shielded cable) but the worst part is the complete loss of linearity near the max/min turn. Any suggestions for some decent pots that don't suffer quite as much from this problem? My thought was to somehow use digital pots (like those in sidewinder joysticks) and switch to usb, but I don't know if thats drastic or even possible?! I would love to be able to achieve that sort of accuracy!I would love to hear any suggestions from people who've overcome these problems!Thanks,Jeff

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Guest PeterK

PeterK The Radio Shack pots are pretty poor but I found on mysetup using the radio shack pots that the 100K pot is tosmall in resistance...there is no way you will run the full swingI ended up using 500K radio shack pots and using only 1/3 to 1/2of the run starting a 10okms and running up to 90k ohmsand not using the rest of the swing of the shaft...You can spend from $5 to $20 for a pot but you need to experimentwith the turn ratio...Many guys use a reduction gear systemto get more control of the pot turning...Im using on some of my controls a SONY 100K pot from the Local parts store...They were on closeout and used on sony beta tape decks..whats great is half way theres a little indentso you know where middle zone is...ALso try a sliding potlike on a mic mixer or graphic equalizer...Pot lubricant or even WD40 can clean up the pots sratchy surface too!!pete http://home.attbi.com/~fs-boneyard

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Guest HepburnUGA

Thanks Pete,I was using a geared system, and I really didn't like the feel of it. I'm going to pick up some sliding pots and give them a try. I like Norbert's setup (kinda reminds me of a cam-shaft in a car) so we'll see how it goes.Thanks!Jeff

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Just a quick couple of qustions. 1st, you said you used a geared system. Are you sure you made the gearing in such a manner that the drive itself is linear? If you just coinnect a sliding rod to a rotating pot, the result is a "sine-wave" shaped drive, not a linear one - this would result in the non-linearity at each end that you describe however good the pots were. The second is probably a silly question - you did buy linear, not audio, pots right? - Audio pots are not linear.Richatrd

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Guest HepburnUGA

Thanks for the response, and great questions!I'll answer #2 first because it's the easiest...yes, I did by linear pots. :)As far as the gearing goes, I used a larger gear (attached to the thrust lever at the axis) that fit into a smaller gear (attached to the rod of a rotary pot). As far as my mechanics goes, I believe it should have produced a linear movement. Thanks!Jeff

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>If you just coinnect a sliding rod to a rotating pot, the result is >a "sine-wave" shaped drive, not a linear one - this would result in >the non-linearity at each end that you describe however good the >pots were. In my setup I used a rotating lever with a sliding pot. The radius was chosen rather big. Of course there is only linearity in the middle part of the lever movement. The first and last third is a kind of sinusoidal.But in practice this turns not out to be any problem. And this kind of construction is veru simple.http://home.wanadoo.nl/norbert.boschregards norbert

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Norbert:>>In my setup I used a rotating lever with a sliding pot. The radius was chosen rather big. Of course there is only linearity in the middle part of the lever movement. The first and last third is a kind of sinusoidal. But in practice this turns not out to be any problem. And this kind of construction is veru simple. You can get around this also by connecting the rotary - sliding pieces in such a way that only the middle part of the travel of the pot is used. and the non-linearity of the ends doesn't come into play. BTW.... I like your Cessna cockpit - That's where I'm trying to go, though with the added feature of building a screen into the panel that displays the instruments, rather than just having pictures of them and the displays on the main monitor. Down the road, if I can, I'd eventually like to replace even that with servo driven 'real' instruments possibly using phidgets, or some sort of PIC interface... but there's a lot of learning before I'm ready to go there Most builders seem to be more interested in "Heavy Iron" cockpits, but my dream is an "As real as it gets" (Whoops, TM infringement? )GA setup.Richard

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Guest HepburnUGA

Ok Norbert, I give up. I can't seem to find ANY sliding pots. Can someone please point me to where they are? I am at my wits end...and I feel like an idiot!Jeff

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Guest MikePowell

Jeff,Slide pot sources:www.mouser.com search on part number 312-9302www.digikey.com search on part number 448XD2104BDNwww.allelectronics.com part no. lsp-100KMikewww.mikesflightdeck.comInfo for simpit builders.

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Guest HepburnUGA

Thanks Mike,You are truly a wealth of invaluable resources.Jeff

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