Title: potentiometers
Post by: arhi on April 27, 2011, 06:35:58 am
Post by: arhi on April 27, 2011, 06:35:58 am
current selection pot on my made in PRC "lab psu" died so I replaced it .. now, as I had few of these "pot in pot" potentiometers (attached is how they are connected internally) I replaced the original "regular" pot one with same value (6k8) pot in pot ... (good that I had proper value) .... the precision of current selection is awesome now :D .. I can select 0.1mA without a problem (with original one 10mA was minimal selectable step) ... anyhow, that's not important ... the actual question is - how the hack are these pots called and can anyone point them to me at farnell/digikey/sureelectronics/itead/seeed as I only have few left and they rule :D (they are not classic multi turn pots, it is actually pot in a pot so you select "region" where you want to have fine adjustment .. it is really hard to explain if you don't see it from picture or try it yourself)
Title: Re: potentiometers
Post by: ian on April 27, 2011, 08:20:20 am
Post by: ian on April 27, 2011, 08:20:20 am
Sounds interesting. Do you have a picture? Are there two adjustment knobs? What is the package like?
I spent some time searching and looking at Google images, but I didn't see anything like this.
I spent some time searching and looking at Google images, but I didn't see anything like this.
Title: Re: potentiometers
Post by: bearmos on April 27, 2011, 01:45:51 pm
Post by: bearmos on April 27, 2011, 01:45:51 pm
i found a pot on digikey with a vernier scale. . .it's intended to give better resolution than a standard multi-turn (i've never tried one).
http://http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SP011-1-11-ND, but i don't think this is what you're describing
http://http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SP011-1-11-ND, but i don't think this is what you're describing
Title: Re: potentiometers
Post by: arhi on April 28, 2011, 02:14:04 am
Post by: arhi on April 28, 2011, 02:14:04 am
[quote author="ian"]Sounds interesting. Do you have a picture? [/quote]
attached, as you can see they are manufactured in USSR (ages ago, I got them from some old guy's closing down the electronics store .. they had a lot of old prc and ussr made parts like pots, elco's etc)
[quote author="ian"]Are there two adjustment knobs?[/quote]
no, single one, but there are 2 pots inside ... example, you turn the pot fully to the left. let's say it is 10K, then you rotate it to the right, and it goes "easy" rotating to the right almost a full circle (few degrees shy from a full circle) and that goes from 0 - 170R to the half of the circle and then start to drop to 128 ohm at the end of the circle (I'm measuring right now), then it gets "bit harder to rotate it" - you feel you catch up and you are rotating something else, now you can continue and now each degree is not changing by few ohm as it was until this moment but now it is more like 100R per degree (~100 times more) .. you turn it a half circle to the right and you get to 5k5 .. then if you back to the left it reduces again by below 2R per degree so a full turn back now will get you down to 5K3
So just like the picture I drawn in the first post, you have "base" pot that do not have an active glider but instead there are 2 gliders few mm apart and they are ends of another pot (much lower value) and it's live glider is your pin3 ... you have full circle turn of that small pot and when you get to the end of that small pot (to the left or to the right) you then "pick up" those 2 end of that small pot that are gliding on the big pot and move them a full circle around the big pot ... pretty neat construction .. just I would like to get more of them, I only have few left :( .... I find this much more precise then the regular 3-5 turn pots
[quote author="ian"]What is the package like?[/quote]
you see the pic :D .. the shaft is 4mm diameter, threaded shoulder is 10mm diameter but the threads are not M10 but something finer, body diameter is 18-20mm depending on the value and body length is 16-25mm
[quote author="ian"]I spent some time searching and looking at Google images, but I didn't see anything like this.[/quote]
I never seen any like this being sold in any electronics shop, maybe they have them under some weird name - no idea .. maybe as regular multiturn pots became cheap to manufacture they don't make ones like this any more .. as I'm sure they are mechanically much more complex then regular multiturn...
attached, as you can see they are manufactured in USSR (ages ago, I got them from some old guy's closing down the electronics store .. they had a lot of old prc and ussr made parts like pots, elco's etc)
[quote author="ian"]Are there two adjustment knobs?[/quote]
no, single one, but there are 2 pots inside ... example, you turn the pot fully to the left. let's say it is 10K, then you rotate it to the right, and it goes "easy" rotating to the right almost a full circle (few degrees shy from a full circle) and that goes from 0 - 170R to the half of the circle and then start to drop to 128 ohm at the end of the circle (I'm measuring right now), then it gets "bit harder to rotate it" - you feel you catch up and you are rotating something else, now you can continue and now each degree is not changing by few ohm as it was until this moment but now it is more like 100R per degree (~100 times more) .. you turn it a half circle to the right and you get to 5k5 .. then if you back to the left it reduces again by below 2R per degree so a full turn back now will get you down to 5K3
So just like the picture I drawn in the first post, you have "base" pot that do not have an active glider but instead there are 2 gliders few mm apart and they are ends of another pot (much lower value) and it's live glider is your pin3 ... you have full circle turn of that small pot and when you get to the end of that small pot (to the left or to the right) you then "pick up" those 2 end of that small pot that are gliding on the big pot and move them a full circle around the big pot ... pretty neat construction .. just I would like to get more of them, I only have few left :( .... I find this much more precise then the regular 3-5 turn pots
[quote author="ian"]What is the package like?[/quote]
you see the pic :D .. the shaft is 4mm diameter, threaded shoulder is 10mm diameter but the threads are not M10 but something finer, body diameter is 18-20mm depending on the value and body length is 16-25mm
[quote author="ian"]I spent some time searching and looking at Google images, but I didn't see anything like this.[/quote]
I never seen any like this being sold in any electronics shop, maybe they have them under some weird name - no idea .. maybe as regular multiturn pots became cheap to manufacture they don't make ones like this any more .. as I'm sure they are mechanically much more complex then regular multiturn...
Title: Re: potentiometers
Post by: sqkybeaver on April 28, 2011, 03:32:41 am
Post by: sqkybeaver on April 28, 2011, 03:32:41 am
i have been working on building a current limited bench ps, using a few opamps and 74ls02n.
i have looked at alot of multi turn pots recently and have not seen anything like that.
i have looked at alot of multi turn pots recently and have not seen anything like that.
Title: Re: potentiometers
Post by: arhi on April 28, 2011, 06:24:44 am
Post by: arhi on April 28, 2011, 06:24:44 am
I found some references
http://www.dayao.com.tw/en/ap_5_35.htm (http://www.dayao.com.tw/en/ap_5_35.htm)
http://www.evita.lt/en/det-17641-potent ... b-10k.html (http://www.evita.lt/en/det-17641-potentiometer-sp5-35b-10k.html)
http://www.elmicom.ru/sp5_35b.shtml (http://www.elmicom.ru/sp5_35b.shtml)
I was getting them fairly cheap (0.5$ per piece) but lost contact of my source
http://www.dayao.com.tw/en/ap_5_35.htm (http://www.dayao.com.tw/en/ap_5_35.htm)
http://www.evita.lt/en/det-17641-potent ... b-10k.html (http://www.evita.lt/en/det-17641-potentiometer-sp5-35b-10k.html)
http://www.elmicom.ru/sp5_35b.shtml (http://www.elmicom.ru/sp5_35b.shtml)
I was getting them fairly cheap (0.5$ per piece) but lost contact of my source
Title: Re: potentiometers
Post by: bearmos on April 29, 2011, 04:16:55 am
Post by: bearmos on April 29, 2011, 04:16:55 am
would a standard 25 turn pot work? if you had 10k / 25 turns, you wind up with a little over 1 ohm per degree of rotation (i'm not sure what sort of accuracy you're looking for). depending on exactly how much variability you need, this might work pretty well. here's an example of a fairly common PCB mount @ $2.56 ea( i realize you've been using panel mounts):
http://http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3296Z-103LF-ND
burns also makes some with better temperature stability, if you'd need it. i'm sure you could find something like this surplus for a lot less.
i have to say. . . $.5 ea for the ones you were getting seems like quite a steal.
http://http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=3296Z-103LF-ND
burns also makes some with better temperature stability, if you'd need it. i'm sure you could find something like this surplus for a lot less.
i have to say. . . $.5 ea for the ones you were getting seems like quite a steal.
Title: Re: potentiometers
Post by: sqkybeaver on April 29, 2011, 05:12:46 am
Post by: sqkybeaver on April 29, 2011, 05:12:46 am
[quote author="bearmos"]would a standard 25 turn pot work? if you had 10k / 25 turns, you wind up with a little over 1 ohm per degree of rotation (i'm not sure what sort of accuracy you're looking for). depending on exactly how much variability you need, this might work pretty well. [/quote]
for my use i will be getting some of the bourns 10k 10 turn panel mount
it will be much easyer to fine tune the current and voltage on a bench power supply.
ill be using some of the 25 turn pcb mount ones for trimming the current amplifier.
for my use i will be getting some of the bourns 10k 10 turn panel mount
it will be much easyer to fine tune the current and voltage on a bench power supply.
ill be using some of the 25 turn pcb mount ones for trimming the current amplifier.
Title: Re: potentiometers
Post by: arhi on April 29, 2011, 07:12:49 am
Post by: arhi on April 29, 2011, 07:12:49 am
[quote author="bearmos"]would a standard 25 turn pot work?[/quote]
I have bunch of those .. 10turn, 25turn .. different resistance ... problem is they are all meant to be "set and left alone" - using a 25 turn pot like one you linked as a voltage or current set pot on a lab psu would be fairly impossible ... first the mechanics of it would be complex (extending the tiny screw to a big button) and secondly I'm fairly sure they'd die quite soon after daily use ...
also this "double" ones allow you to fast go to the ballpark figure and then fine tune it .. so from 0 - 20V you get in a turn and then fine tune it by 0.01V .. with a 25 turn pot, you need to make 20 turns ..
something like http://uk.farnell.com/vishay-spectrol/5 ... dp/1144786 (http://uk.farnell.com/vishay-spectrol/534b1103jlb/potentiometer-2w-10k/dp/1144786) or http://uk.farnell.com/bourns/3549s-1aa- ... dp/1470221 (http://uk.farnell.com/bourns/3549s-1aa-103a/precision-pot-7-8-22mm-dia-10t/dp/1470221) would solve the mechanical problem but this babies are all but cheap ... (few of these cost more then my psu :( )
I have bunch of those .. 10turn, 25turn .. different resistance ... problem is they are all meant to be "set and left alone" - using a 25 turn pot like one you linked as a voltage or current set pot on a lab psu would be fairly impossible ... first the mechanics of it would be complex (extending the tiny screw to a big button) and secondly I'm fairly sure they'd die quite soon after daily use ...
also this "double" ones allow you to fast go to the ballpark figure and then fine tune it .. so from 0 - 20V you get in a turn and then fine tune it by 0.01V .. with a 25 turn pot, you need to make 20 turns ..
something like http://uk.farnell.com/vishay-spectrol/5 ... dp/1144786 (http://uk.farnell.com/vishay-spectrol/534b1103jlb/potentiometer-2w-10k/dp/1144786) or http://uk.farnell.com/bourns/3549s-1aa- ... dp/1470221 (http://uk.farnell.com/bourns/3549s-1aa-103a/precision-pot-7-8-22mm-dia-10t/dp/1470221) would solve the mechanical problem but this babies are all but cheap ... (few of these cost more then my psu :( )
Title: Re: potentiometers
Post by: Sjaak on April 29, 2011, 11:32:45 am
Post by: Sjaak on April 29, 2011, 11:32:45 am
Would this solve the issue: http://uk.farnell.com/vishay-spectrol/1 ... erch=true& (http://uk.farnell.com/vishay-spectrol/11a11b10/counting-dial-analog-10-turn/dp/1144732?crosssellid=1144732&crosssell=true&in_merch=true&)
It looks like you could turn in quickly and finetune afterwards, no experience with those though.
It looks like you could turn in quickly and finetune afterwards, no experience with those though.
Title: Re: potentiometers
Post by: bearmos on April 29, 2011, 12:50:47 pm
Post by: bearmos on April 29, 2011, 12:50:47 pm
@Sjaak
Digikey also has a bunch available (an example is in my first reply). these do look interesting, but i've also never tried them before.
Digikey also has a bunch available (an example is in my first reply). these do look interesting, but i've also never tried them before.
Title: Re: potentiometers
Post by: voidptr on May 01, 2011, 07:58:27 am
Post by: voidptr on May 01, 2011, 07:58:27 am
@arhi
interesting pot, i used 2 standard big pots 1 coarse and 1 fine last time i had to have precise adjustment over a big range. single button like your are more nice tho. i found long time ago a different version, push down and turn for coarse or just turn for fine adjustment.
interesting pot, i used 2 standard big pots 1 coarse and 1 fine last time i had to have precise adjustment over a big range. single button like your are more nice tho. i found long time ago a different version, push down and turn for coarse or just turn for fine adjustment.
Title: Re: potentiometers
Post by: arhi on May 01, 2011, 04:39:47 pm
Post by: arhi on May 01, 2011, 04:39:47 pm
bearmos, I think that would be overkill for a lab psu :) .. also I'm not fond of the price ...
void* yeah I seen those one some equipment while back ..
these look pretty non standard, I contacted my old source to check if he has more ..
void* yeah I seen those one some equipment while back ..
these look pretty non standard, I contacted my old source to check if he has more ..
Title: Re: potentiometers
Post by: bearmos on May 01, 2011, 09:21:56 pm
Post by: bearmos on May 01, 2011, 09:21:56 pm
arhi, i certainly agree. your "pot within a pot" solution is very elegant, especially at $.50 a piece! when i had suggested the PCB mount 25 turn pot, i guess i didn't really realize your exact application. if your source has more, you'd probably do well to load up on them at such a great price!
Title: Re: potentiometers
Post by: arhi on May 01, 2011, 09:42:39 pm
Post by: arhi on May 01, 2011, 09:42:39 pm
yup ... I am still waiting for his reply :( .. but I kinda plan to get all he has :) .. I really like them ..
Thing is, when I was getting them for the first time, I figured how cool they were but had no wish to stock them as I assumed they are fairly standard equipment .. and now when I actually tried to find one online, not only I did not find them, most ppl had no idea what I'm talking about..
The 2 pots for course / fine adjustments are a nice solution but you need to develop your application for them, I have some "premade" stuff that I just want to improve by using multiturn pots and regular 10 turn "big ones" are notoriously expensive .. way more then I expected in the first place
Thing is, when I was getting them for the first time, I figured how cool they were but had no wish to stock them as I assumed they are fairly standard equipment .. and now when I actually tried to find one online, not only I did not find them, most ppl had no idea what I'm talking about..
The 2 pots for course / fine adjustments are a nice solution but you need to develop your application for them, I have some "premade" stuff that I just want to improve by using multiturn pots and regular 10 turn "big ones" are notoriously expensive .. way more then I expected in the first place
Title: Re: potentiometers
Post by: sqkybeaver on May 02, 2011, 12:50:29 am
Post by: sqkybeaver on May 02, 2011, 12:50:29 am
[quote author="arhi"]yup ... I am still waiting for his reply :( .. but I kinda plan to get all he has :) .. I really like them .. [/quote]
I'd like to try a couple of them, i have not seen them any ware,
I'd like to try a couple of them, i have not seen them any ware,
Title: Re: potentiometers
Post by: arhi on May 02, 2011, 01:02:10 am
Post by: arhi on May 02, 2011, 01:02:10 am
if I manage to get some, you can have few ... I just hope this guy still have some :( ... I have no idea why I hadn't picked up a whole lot .. he and his partner were closing down some repair shop or something similar in some village and were selling the huge amount of spare parts they had ... lot of military components, some german, some russian ... I took all the power transistors they had :D and all the zeners they had but that's it ..
Title: Re: potentiometers
Post by: sqkybeaver on May 02, 2011, 01:45:06 am
Post by: sqkybeaver on May 02, 2011, 01:45:06 am
that would be cool, ill pay shipping ect.
Title: Re: potentiometers
Post by: arhi on May 02, 2011, 02:02:51 pm
Post by: arhi on May 02, 2011, 02:02:51 pm
I just hope we both get some :) ... it's still "holiday's" here (they finish tomorrow), but it is possible ppl "connected" some so I actually expect reply next monday ... if I don't get any by then, I'll start to get worried
Title: Re: potentiometers
Post by: arhi on May 10, 2011, 06:28:49 pm
Post by: arhi on May 10, 2011, 06:28:49 pm
the price changed (more then ten times as they no longer have many of them, but it is still fairly cheap - bit under 5E per piece) but I managed to get a bunch this babies from the same source... they should arrive tomorrow :)