Potentiometer  - Page 1
Forum section: electronics / beginners

author: Dell
author_rank: Contributor
timestamp: January 30, 2022, 03:36:24 pm
content: I have my Pultra lathe running on a industrial sewing machine motor but I want to change to a potentiometer someone sent me a diagram on how to do it but not being an electrical wiz ( or any wiz for that matter ) I am hoping that someone on here is and can explain it to me in idiot terms , I know that there three pins but does it matter what outside pin goes to what or can it be either, the diagram said make sure it’s earthed ( make sure what is earthed )I presume because it’s going in a cast metal box that to motor , and add a resistor 3K3 1/2W , have googled but no help, so if there is anyone on here that could explain things it would be much appreciated.

author: ledtester
author_rank: Super Contributor
timestamp: January 30, 2022, 04:17:49 pm
content: In the case of the 3-turn pot -- Farnell part 1470239:https://uk.farnell.com/bourns/3547s-1aa-103a/precision-pot-7-8-22mm-dia-3t/dp/1470239?ost=1470239the pinout and relationship to the electrical schematic is imprinted on the device itself -- pin 2 in on the end and 1 and 3 on on top:In the case of the single turn pot -- Farnell part 2328038:https://uk.farnell.com/bourns/91a1a-b28-a15l/potentiometer-linear-10kohm-10/dp/2328038?ost=2328038the pins are labelled 1-2-3 from left to right when looking at it from the front and the relationship is:I got these images from the "datasheet" link on the Farnell product page for each potentiometer.In both cases pins 1 and 3 are essentially interchangeable -- i.e. the potentiometer will serve its function if you choose to connect pin 1 or pin 3 to the 3K resistor (and the other to the Rb connection). The difference will be whether turning the pot clockwise will increase or decrease the motor speed.

author: Paul B
author_rank: Contributor
timestamp: January 30, 2022, 05:15:47 pm
content: OK DelHopefully the other reply has sorted you out , as the circuit diagram You have posted is a good start alternativelyI assume there is a switch at the moment with a few set speeds ?i assume the person that did the drawing has Sean your unit or has the same unit other wise the wire colours might not be correcta picture of the back of the switch might help us to help youthe drawing has 3 wires and are Red Green and Black are the wire colours the same on the switch ?The resister is there to help use the pot fully as without the 3.3 K resister there would be no change for the first 1/ 3 of the pot movementif you want more help just PM me and we can talk on the phonePaul West Sussex

author: Dell
author_rank: Contributor
timestamp: January 30, 2022, 07:09:40 pm
content: Thanks for replyYes he has the same motor so the three colours are the same , the way the motor is controlled now is by a pedal that pulls a leaver down , I have opened the box up and the three wires are on a pcb with a little black thing on it and the leaver just moves a magnet over it .I will PM you if that is ok but I won’t disturb you on a Sunday evening.This is the motor , apart from the pedal operation I love it so much torque.

author: Dell
author_rank: Contributor
timestamp: January 30, 2022, 07:28:53 pm
content: Some more pictures

author: Dell
author_rank: Contributor
timestamp: January 30, 2022, 07:45:41 pm
content: Many thanks

author: Paul B
author_rank: Contributor
timestamp: January 30, 2022, 09:44:04 pm
content: Hi how much does the motor and controller cost ?

author: Dell
author_rank: Contributor
timestamp: January 31, 2022, 06:53:46 am
content: I paid £99 of eBay

author: Dell
author_rank: Contributor
timestamp: February 04, 2022, 03:19:22 pm
content: Hi PaulOk the pot works but it doesn’t start as soon as I turn the dial thereabouts first 1/4 turn and only half the pot does anything, is it possible to use more of the pot , if so will it make difference , if so what difference, is it worth it , again if it’s worth doing how to do it.Thanks DellFor some reason the picture is on its side.

author: Paul B
author_rank: Contributor
timestamp: February 04, 2022, 03:59:46 pm
content: Hi Dellas i explained on the phone the resisters are there to make beater use of the pot without them you will find that part of the pot rotation does nothingso happy to talk you through it on the phoneso have you connected the 10 K pot as the Drawing ?have you connected the 3K3 fixed resister in the black lead then connected the other end of the resister to the Pot ?which end of the pot is dead ante clock wise or clock wise amusing clock wise is faster speedRegards Paul

author: Dell
author_rank: Contributor
timestamp: February 04, 2022, 05:40:22 pm
content: The last part is dead , yes clockwise is faster , white mark on knob is about 11 if you think of it as a clock face it starts about the 1 gets faster until about the 4 or 5 then nothing to stop about the 8 , hope that makes sense thinking of it as a clock face.Dell

author: Paul B
author_rank: Contributor
timestamp: February 05, 2022, 01:53:03 pm
content: assuming you have used a 10 K pot and a 3k3 resister on the anty clock wise end of the pot (slow speed end )and the lowest speed is achieved then remember the 1 K resisters i suggested you ordertrying putting 2 in series with the red wire that goes to the clock wise end of the pot and see if this improves thingsnoting that the pot terminals could be at a high voltage so must be switched off

author: Dell
author_rank: Contributor
timestamp: February 05, 2022, 03:25:22 pm
content: Thanks Paul just to get it clear in my mind, in series is one after the other, inn parallel is side be side, apart from perhaps more working area would there be any benefit.Dell

author: TimFox
author_rank: Super Contributor
timestamp: February 05, 2022, 04:38:02 pm
content: A suggestion: when looking for information about motor control or other specific topic, the "Subject" line should be more restrictive than "Potentiometer" to attract relevant information.

author: Paul B
author_rank: Contributor
timestamp: February 05, 2022, 11:26:47 pm
content: Hi Tim i would agree but this gentleman is new to electronics that is why i am being extra gentleregarding series this is like frankfurters in a stringparallel is like a bunch of Banners with all the heads tied together and all the tails tied togetherso we are trying to make all the pot user bull rather than only part of the pot userbull as infully anty clock minimum speed fully clock wise max speedforgive the spelling but that is mePaul B

author: Dell
author_rank: Contributor
timestamp: February 07, 2022, 10:50:23 am
content: Thanks Pail I will give that a try.Dell