How to wire a 10 kOhm linear potentiometer?

Other Hardware General Electronics
1

I use a potentiometer to set the contrast of a LC Display; I tried the plastic button potentiometer from the Arduino Starter Kit but found it very troublesme: its pins do not stick correctly on the breadboard, and it's both over and undersensitive (ie, if one turns the knob only a little, nothing happens; if one then turns a little more, contrast changes completely, not gradually).

I bought linear potentiometers (there was no reference on them; they're around 1 inch long, metal-coated, and "ALPHA" is written on the metal); but I don't understand how I'm supposed to plug them?

There are apparently two pins at one end and one pin on the other end, as well as four legs that seem not to be connected to the electronic parts.

But the pins there too do not plug correctly into the breadboard, and they have nearly the same size as the legs: so, how to wire them?
Worse, I think that the two pins on the same end are to be wired one to ground and one to 5V, which means that I need to wire them perpendicularly to the breadboard. But the potentiometer is longer than the breaboard is large, so I really don't understand how it's supposed to be wired...

2

Website where you bought them? Pictures? Ohmmeter readings?

3

How did you have the other potentiometer wired up? Schematic?

4

LienRag:
I use a potentiometer to set the contrast of a LC Display; I tried the plastic button potentiometer from the Arduino Starter Kit but found it very troublesme: its pins do not stick correctly on the breadboard, and it's both over and undersensitive (ie, if one turns the knob only a little, nothing happens; if one then turns a little more, contrast changes completely, not gradually).

The best way to fix the issue of insertion is to extend the pins of the device, by soldering on some wires.

LienRag:
I bought linear potentiometers (there was no reference on them; they're around 1 inch long, metal-coated, and "ALPHA" is written on the metal); but I don't understand how I'm supposed to plug them?

There are apparently two pins at one end and one pin on the other end, as well as four legs that seem not to be connected to the electronic parts.

Without pictures, it is difficult to to come to a conclusion, but I would be willing to bet that the four "legs" are metal tabs (or similar) meant as non-connected mechanical mountings; they are meant to be mated with holes in a PCB and soldered into place.

The other three terminals are the two ends of the potentiometer, and one for the wiper.

LienRag:
But the pins there too do not plug correctly into the breadboard, and they have nearly the same size as the legs: so, how to wire them?

Again, without pictures I can't tell you exactly, but likely those four "legs" can simply be snipped off or otherwise removed. However, that still leaves the issue of the other three pins, because they likely won't fit the breadboard, and also likely are not on a standard 0.1" spacing for the breadboard. So - again - soldering on jumper wires would be the best solution (and you wouldn't have to trim the legs off, either).

LienRag:
Worse, I think that the two pins on the same end are to be wired one to ground and one to 5V, which means that I need to wire them perpendicularly to the breadboard. But the potentiometer is longer than the breaboard is large, so I really don't understand how it's supposed to be wired...

Pictures please! But again, soldered on wires would be your best solution to these problems. Finally, to determine what pins are what, use your multimeter to measure the resistance between each pair of pins. Two of the pins won't change resistance when the wiper is moved, indicating those pins are the "ends" of the potentiometer. You can confirm this by measuring from the (supposed) wiper pin to the other two pins; the total of the resistance measurements should be the same (or close enough) as between the "end" pins.

5

I bought linear potentiometers (there was no reference on them; they're around 1 inch long, metal-coated, and "ALPHA" is written on the metal); but I don't understand how I'm supposed to plug them?

There are apparently two pins at one end and one pin on the other end, as well as four legs that seem not to be connected to the electronic parts.

But the pins there too do not plug correctly into the breadboard, and they have nearly the same size as the legs: so, how to wire them?

Not everything plugs into a breadboard. 99% of parts are designed to be soldered to a printed circuit board (either thru-hole or surface mount).

So if you are going to use a breadboard, you have to be creative and "adapt". Maybe solder some wires to the pot, or if you don't have a soldering iron maybe some clip-leads and wires.

For certain surface mount packages there are adapter boards that you solder the part to, then you can plug the adapter into a breadboard. (But, you won't find that for a pot.)

Those extra pins are probably for mechanical strength when the pot is soldered to a PC board.

As polymorph says, a multimeter would be really useful. If you don't have one and cost is a consideration, you don't have to buy an expensive one. You can find them for $10 or $20. Most of the time when you are measuring voltage, resistance, or current you aren't trying to make a super-accurate measurement, you just want to know if you are in the ballpark, or if the voltage is there or not, or if there is even a connection, etc.

But, when you are buying components, don't but the cheapest thing you can find on eBay or Alibaba. Buy from reputable suppliers where they give you a manufacturer's part number and you can look up the manufacturer's datasheet.

....I've built quite a few permanent hobby projects with breadboards. But for complicated designs with high-density high-pincount ICs, most companies skip the breadboarding stage and go straight to prototyping with a custom PC board. This is expensive and the first-pass PC board might have to be modified or it might have errors that make it useless and it gets scrapped. But for a company, it's just part of the R&D budget and it can be faster, cheaper, and more efficient than paying an engineer or technician to hand-wire a breadboard.

6

Given you are using regulated 5V, try just connecting a 220 ohm resistor from Vo (pin 3) to Gnd.

This will work fine most of the time. Try swapping it with 470 ohm, or just grounding Vo to see which is best then you might use other values. You mostly do not need a potentiometer.

7

Thanks all.
Soldering is my nightmare (I'm not good at programming or electronics either, but at least I enjoy trying them...), apparently I'll have to make do.

About removing the potentiometer, I've read that temperature conditions will change the optimal voltage for LCD contrast, so a potentiometer is actually a much better solution than a resistor?

8

LienRag:
Thanks all.
Soldering is my nightmare (I'm not good at programming or electronics either, but at least I enjoy trying them...), apparently I'll have to make do.

About removing the potentiometer, I've read that temperature conditions will change the optimal voltage for LCD contrast, so a potentiometer is actually a much better solution than a resistor?

Well, there's only one way to make soldering not your nightmare, that's to get to some soldering. Everybody who solders quite probably struggled with it at first. We all practiced, and got better at it.

Yes, the optimal voltage will change with the temperature, but you're working on a breadboard... I'm willing to bet you're probably not going to be experimenting with your arduino and display in the extremes of the temperature range. Once you find the ideal voltage for your general room temperature, you'll probably find you don't have to change it a lot (10 degrees one way or the other isn't going to make your display unreadable). If you're planning on moving it around a lot into less temperature controlled environments, you're probably at the stage you need to get working on those soldering skills so that the whole project holds together when you're moving it...