componentsdimmerresistors
I'm trying to solder together a small LED array with a dimming knob out of a bunch of old parts I have laying around, but I can't seem to identify how to wire this component:
The two connectors at the top are labeled A and B and it says ALPHA in the middle.
The red plate is labeled 1 3.
Any help would be appreciated. Thanks!
It's hard to guess from the pictures you've posted, but it looks like a simple LCD module. Here's what I can tell from the desciption:
To make use of this display, you'd have to figure out the connections and make a PCB to to fit the zebra strip precisely. If I were you, I wouldn't bother trying to make use of this thing and would instead crack it open and see if there is anything interesting inside (hint: there probably isn't).
It's a snap-on ferrite core which, when clamped over a number of conductors, becomes part of a common-mode choke. Here is a complete datasheet for a similar product.
The ferrite is lossy so it is better characterized as an impedance at a given frequency. In the case of my example, every wire that goes through the core behaves like it has 241 ohms in series @ 100MHz but only for common mode voltage. If current is going in and out through a pair of conductors the magnetic fields cancel and it acts pretty much like a pair of wires for that current. Unbalanced current (say to ground) will behave like it has the impedance in series.
It is very important to make sure that all the wire pairs that carry significant current are contained within one core, otherwise the core will saturate and the benefit will be lost.
A typical application of such a core would be for wiring to a noisy source such a VFD (motor drive).
Looping the wires \$n\$ times through the core will increase the impedance by a factor of \$n^2\$. Again, every wire must be looped the same number of times to get the full benefit.
Best Answer
This looks like a potentiometer with a built in on-off switch on the back.
When you either push on the knob or turn it to the end of it's range does the resistance between A and B change from infinite to 0 ohms? If so, you have confirmed that it is a switch.
The resistance between 1 and 3 should be fixed and between 1 & 2 (or between 2 & 3) vary as you turn the knob.
These are (were) commonly used as combined volume controls and on-off switches on radios before the digital age.
In response to the comment.
Since you measured an exponential change in resistance you have what is known as a logarithmic taper potentiometer. The other type is a linear taper. Logarithmic taper is used for volume controls since human hearing does not respond linearly but rather on a decibel scale.
If you measured across 1 & 2 instead of 2 & 3 you would have perhaps found the switch as "on" when the potentiometer is "on" as you put it. Looked at another way, the resistance across 1 & 2 will increases as the resistance across 2 & 3 decreases. In fact the resistance between 1 & 3 should remain constant as you turn the knob. Also for any place you put the knob, if you add up the resistance between 1 & 2 with the resistance between 2 & 3 that total should equal the resistance between 1 & 3.