Some electronics help

[abunaitoo]

So I'm trying to power a 12vdc wiper motor, through this box.
I want the dial to be more sensitive at lower speeds.
What's happening now is I can get it slow, if I turn the dial less than 1/8.
I would like it to be more gradual over a wider range on the dial.
The potentiometer in it is B10k.
Would it be as easy as changing it to a B5k or B1k????
Hope I'm making sense.

[45_Colt]

What can be done is to add another pot in series with the current one. Using a 1K will make it a 'fine tuning' knob. Rough it in with the main 10K pot, then do the final adjustment with the 1K.

45_Colt

[challenger_i]

+1 for 45_Colt.

[jdgabbard]

So a B10K is a linear taper potentiometer. What this means is that the voltage taper curve of adjusting the knob is going to be linear from one end to the other. However, because of the way ohms law works, in application of voltage dividers the voltage output is not going to be linear.

This is solved in audio applications by the use of a logarithmic potentiometer. The taper curve produced by this type of potentiometer is a more natural perception of a linear change in audio circuitry. This can also be used in other applications to provide the same type of result.

Addition of a second POT for a coarse/fine adjustment also works fine. Sometimes a logarithmic pot works better.... Depends on the specific application.

See this page for details about the difference in the pots. https://eepower.com/resistor-guide/r...ometer-taper/#

Edit: Also, you don't really mention what this is for. Looking at your attached picture I presume you're repairing a motor speed controller of some sorts... If that is the case, you should probably take a look at schematics for phase-angle controllers. It's a very interesting type of circuit, and directly applicable to what you're doing...

[abunaitoo]

So is the logarithmic potentiometer the same as a audio potentiometer?????
Would there be an "A" in place of the "B", or is it the one with no letter in front????
I'm trying to make a variable speed feeder, that moves a spring loaded arm, to push one part at a time.
Just a "for fun" project.
The "phase-angle controller" looks interesting.
Is a SCR the samething????
Would a SCR work????
Is what I have an SCR????
amazon has one for a cheap price.

Would have to change the out put from AC to DC.

[abunaitoo]

So I found a hot wire foam cutting box,
Also found a variable transformer.
Wonder if any of these would work.
Probably would need to change from AC to DC.

[JonB_in_Glencoe]

If your B10k pot is in the basic voltage divider circuit, and you don't need the higher speed (from 40 to 100), then you could put a 20K resistor in series with the 'high' leg of the B10k pot. That would make the speed from 0 to 40 and stretch it out to 0 to 100...hence making the low end more sensitive.

[jdgabbard]

An Audio Potentiometer is a Logarithmic Pot. But not all Logarithmic Pots are Audio Pots. You'll have to find one suitable for your application, yes an A10K is a logarithmic taper 10k pot. But, that is not the actual part number, more a type identifier. You'll have to look at the ratings to determine what you need.

I'm by no means an electrical engineer, more of a hobbyist. And I primarily work on digital circuits, not analog, and ever more rare for me to work on AC.... SCRs are often used in phase angle control, but it's just a component within a larger circuit. As for variable transformers and the like, I don't think that is something you'll want to mess with.

If your circuit is primarily DC Analog, it may be easier to use PWM to achieve your desired duty cycle. Essentially PWM is a time delayed On/Off state of a digital signal. In other words, it can be on 25% of the time and off 75% of the time, or 50/50, or 33/66, etc... You can acheive this with a simple 555 timer. If you need to step up voltage or control AC you can simply use an SSR with the gate being controlled by the 555. It's actually pretty easy to do this...

Check out this article. https://www.electronicshub.org/555-timer-pwm/

[challenger_i]

Once One is to the point of using Pulse Width Modulation, One may as well use one of these:

[jdgabbard]

Once One is to the point of using Pulse Width Modulation, One may as well use one of these:

Depends on what you're doing..... But yeah, self contained is always nice if they have it. I have a lot of discreet parts, so sometimes it's just easier for me to use what I have. I used a 555, an Op-Amp, a Thermister, an SSR, and a DC heating element to created an adjustable heater for an enclosure on one of my 3d printers at one point. Worked well enough for what I was doing, and saved some money over buying a ready made solution.

But I think that is what tinkering is all about. Using what you have, or can get, to make what you want...

[.429&H110]

I had a junk treadmill that I salvaged the motor and dashboard power control out of.
Carpenter shop got it for a variable speed bench grinder with fine grit wheels
That DC motor had awesome torque, turning slowly.

Was my first look at PWM, cool beans.

[Half Dog]

Take your vehicle to the shop.

[abunaitoo]

Putting two pots in series sounds like something I can do.
I will see what I have as far as pots go, and give it a shot.
Worse I could do it burn something out.

I do have a few cheap PWM I got off evil bay.
Did manage to burn one out.
Maybe I'll try that again.

[abunaitoo]

Thought just came to me.
Could that white box I'm trying be PWM?????
Has all kings of electronic stuff inside of it.
This is getting really interesting.
Starting to learn again.
Haven't done that for years.

[elmacgyver0]

You may want to gear down the motor or use a jack shaft like a lathe uses.

[MaryB]

Thought just came to me.
Could that white box I'm trying be PWM?????
Has all kings of electronic stuff inside of it.
This is getting really interesting.
Starting to learn again.
Haven't done that for years.

Do you have a link to where you got the box to give us more info?

[poppy42]

Well, I don’t have a clue what any of you guys are talking about! And frankly my dear I don’t give a damn lol

[.429&H110]

As I understand it from a pipefitters point of view...

A 12V DC motor is a spinning magnet
more VA (volt-amps) it goes faster, less it goes slower.
But to slow it down to maybe 1 volt, there won't be enough magnet.
So we make 12v zaps, pulses, and the motor will have enough magnet to be useful.

Electronic motor control is the future and a big subject.

[MaryB]

As I understand it from a pipefitters point of view...

A 12V DC motor is a spinning magnet
more VA (volt-amps) it goes faster, less it goes slower.
But to slow it down to maybe 1 volt, there won't be enough magnet.
So we make 12v zaps, pulses, and the motor will have enough magnet to be useful.

Electronic motor control is the future and a big subject.

Not the future! It is real life! Furnaces, air conditioners, washing machines... all are using permanent magnet PWM motors now to control speed and be more energy efficient. Side benefit is when that appliance is worn out those motors work as electric generators in home built wind turbines! Often the motor control module is what goes bad, a part not needed to use it to generate electricity!

[abunaitoo]

Got them from amazon.
Here's the link.
It doesn't say it's PWM, so I'm thinking not.
https://www.amazon.com/gp/product/B0...RHWISCA2E&th=1