Post by thread:[EE] long-life potentiometers

I need a small, single-turn pot that has a long wiper life and low noise during travel. Something like a servo feedback pot, but tiny. Are there any non-contact components (optical?) that can accomplish this? Recommendations welcome as always. Thanks. -Derek Cowburn -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

Do you need to have absolute reading (that is, when power is restored, do you want to be able to read the absolute position?). Does it have to be resistive ? How about using an optical encoder ? Search DigiKey for 'encoder' (and then select Encoders from the Switches category). BTW, every cheap mechanical mouse has a pair of them. Tal > {Original Message removed}

> Do you need to have absolute reading (that is, when power is > restored, do you want > to be able to read the absolute position?). yep. It's a servo feedback input. I'll feed it into the A/D on an '876. > Does it have to be resistive ? I guess hall sensors could work. I should be able to use two bipolar hall sensors and a small magnet, yes? Kind of like an analog version of the optical encoder. hmmmm... > How about using an optical encoder ? Not sure if I can get one that gives 10-bits resolution in a 1/4" package. The hall sensor idea has intrigued me. Anyone else done this? -Derek Cowburn -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Perhaps you could contact the makers of RC Servos for sources of pots that they use. I would imagine that the pot in micro servers would be very tiny (and probably cheap too!) {Original Message removed}

Yea, I've looked at some tiny servo pots but there's not enough markings to determine the make & part#. I was going to pick something from DigiKey but I wanted to know the best TYPE of pot for this application. Thanks. -Derek > {Original Message removed}

> I need a small, single-turn pot that has a long wiper life > and low noise > during travel. Something like a servo feedback pot, but tiny. > > Are there any non-contact components (optical?) that can > accomplish this? > > Recommendations welcome as always. Thanks. As you need it tiny, I suspect it may be practical to think about making your own LVDT sensor. If the travel is short enough then you could probably use a potcore winding former for the windings, and a ferrite slug as the moving element. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

You might look into a MAX5427 or like... {Quote hidden}> > -----Original Message----- > > From: Alan B. Pearce [.....A.B.PearceKILLspam@spam@RL.AC.UK] > > Sent: Monday, August 05, 2002 11:07 AM > > To: PICLISTKILLspamMITVMA.MIT.EDU > > Subject: Re: [EE] long-life potentiometers > > > > > > > I need a small, single-turn pot that has a long wiper life > > > and low noise > > > during travel. Something like a servo feedback pot, but tiny. > > > > > > Are there any non-contact components (optical?) that can > > > accomplish this? > > > > > > Recommendations welcome as always. Thanks. > > > > As you need it tiny, I suspect it may be practical to think > > about making > > your own LVDT sensor. If the travel is short enough then you > > could probably > > use a potcore winding former for the windings, and a ferrite > > slug as the > > moving element. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Sun, 4 Aug 2002, Derek Cowburn wrote: >I need a small, single-turn pot that has a long wiper life and low noise >during travel. Something like a servo feedback pot, but tiny. > >Are there any non-contact components (optical?) that can accomplish this? Hall potentiometer ? Optical is possible too. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Derek Cowburn wrote: > > I need a small, single-turn pot that has a long wiper life and low noise > during travel. Something like a servo feedback pot, but tiny. > > Are there any non-contact components (optical?) that can accomplish this? Yes, a tiny (good quality) trimmer capacitor. Multi-plate work best, people have said that the top/bot plate ones are too low (a few pF) and accuracy is bad. I have found the large ones from transistor radios are excellent for position use, the only hardware is one schmitt inverter 7414 (as a high speed osc) etc and one resistor and cap. So you can get 6 rotary sensors driven with one 7414 chip. Then check the osc speed by counting pulses/PIC clocks or vice versa. Accuracy is good for 8 bits or so. -Roman -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>> As you need it tiny, I suspect it may be practical to think >> about making >> your own LVDT sensor. If the travel is short enough then you >> could probably >> use a potcore winding former for the windings, and a ferrite >> slug as the >> moving element. >That sounds interesting. Can you describe a circuit and >how to interface it to the PIC A/D? I do not know a lot about the inner workings, but have a look at an application note on this site. http://www.anadigm.com/data-library.html and look for AN004, it explains the theory quite well. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

A very cool link. Too bad I hadn't seen this device a bit sooner, since I just completed updating an old DVDT/positioner design!!! Oh well, someday it will need another update.... Chris > have a look at an > application note on this site. > http://www.anadigm.com/data-library.html and look for AN004, -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics