Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Trim Pot

Status
Not open for further replies.

joeyb

New Member
I have a silly question regarding the wiring of a trim pot. Are all three wires necessary? It seems to me that you only need to wire up one of the ends and the variable lead in order for it to work(changing only which way is high and low depends on which end is connected)?? Or do you have to loop the trimmer lead back to the incoming or outgoing side? I see on some schematics only two leads wired up, and on others the trimmer is looped to one of the sides. Is there a reason for this? Thanks for the help!

Joe
 

Optikon

New Member
joeyb said:
I have a silly question regarding the wiring of a trim pot. Are all three wires necessary? It seems to me that you only need to wire up one of the ends and the variable lead in order for it to work(changing only which way is high and low depends on which end is connected)?? Or do you have to loop the trimmer lead back to the incoming or outgoing side? I see on some schematics only two leads wired up, and on others the trimmer is looped to one of the sides. Is there a reason for this? Thanks for the help!

Joe

You are right. In the actual component, you get exactly what you see with the schematic symbol. Use it as you see fit, 2 or 3 connections.
 

Klaus

New Member
The answer is yes and no :D , depending what you want to do with the trimpot. If you just want a variable resistor then connect one end and the wiper together and use the other end and wiper as variable resistance.

If you want a voltage divider you connect +V at one end, 0 (or -V) at the other and pick up your variable voltage from the wiper.

Hope that explains it.
 

Phasor

Member
joeyb said:
Are all three wires necessary?

2 leads for a variable resistor.
3 leads for a voltage divider.

I see on some schematics only two leads wired up, and on others the trimmer is looped to one of the sides. Is there a reason for this?

There is no reason that I am aware of. I can only guess that it's just a convention. It's not really necessary.
 

Sebi

Active Member
The wiper and one end connecting was needed for wrong quality pots, because while adjusted cannot produce higher resistance as nominal.
Sometimes this effect damaged the circuit. (open loop)
 

joeyb

New Member
Schematic.....

Thanks for the information guys. I kind of figured that was the case. I am building a power supply using an NTE923D regulaotr. I have to put a trim pot into the Vref pin (along with a potentiometer for adjusting voltage), and according to the schematic I am not sure how to connect it up. I am used to seeing pots as a different schematic symbol than this so I am confused. I have added an attachment (small image showing the schematic piece in question). R2 is my concern. Thanks so much for all the help so far and any help I can get.

Joe
 

Attachments

  • Power_Supply_167.gif
    Power_Supply_167.gif
    2.6 KB · Views: 1,651

Sebi

Active Member
With trimpot You can adjust the span voltage. Other pot is a voltage adjuster on frontside of PSU. E.g.: the specification says the output adjustable from1,5 to 24V, just turn the pot on front to max., measure the output voltage, and adjust it to 24V with trimpot.
 

joeyb

New Member
Wiring

Sebi,

Thanks for the response. I see what the two resistors have to do, however, my question is regarding the wiring. The R2 trim pot symbol looks to me like the slider is wired back to the top, as in the RED wire in the adjusted schematic i drew below. Is this the way it should be soldered on the board? Like i said I am not used to seeing a trim pot represented by this symbol I am used to the resisitor w/ arrow wiper. And with that symbol it is easy to tell how it is wired. How do I tell how this symbol is wired?? Thanks, and sorry for the dumb questions!!

Joe
 

Attachments

  • Power_Supply2.GIF
    Power_Supply2.GIF
    2.6 KB · Views: 1,166

Sebi

Active Member
Yes, Your wiring is correct, the middle-pin is the wiper,possible connecting to one end of resistor. If You choose the other end, the increase of resistance accomplished by turning anticlockwise.
 

bmcculla

New Member
If you are using the pot as a variable resistor you can set the failure state by connecting the wiper to the unused lead. So if the pot breaks after a lot of use and the wiper becomes disconected you will still have a resistance that is within your limits.

Brent
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top