Urgent help needed on how to control an atomizer humidifier using voltage instead of a potentiometer

Thread Starter

nycokello

Joined Aug 10, 2009
35
Hello members ;
I'm planning to modify the humidifier shown in the photo so that I can increase or decrease it's rate of humidification using a voltage ramp up or ramp down respectively ; instead of it's 10k rheostat being used. I know in one approach is to use a digital potentiometer link to other auxiliary circuits. But i can't get a digipot in our local shops here in Kenya.
This humidifier also has a mechanism of shutting down (even if it's switched on) when it's vibrator is not covered with water. And I was thinking that it could be possible to link this this feature to some sort of auxiliary PWM circuits to control it's output. But i can't get it's electronic circuit diagram online.
Is there anyone here who can help me with it's circuits or a similar circuit ; or any other alternative approach for me to implement my idea....

Mod edit: remove all caps in title.
 
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#12

Joined Nov 30, 2010
18,076
As, "not a Mod" I can only guess that there are limits for beginners...intended to slow down spam attacks.
So I asked the Moderators. The ball is in their court and I don't know what the limitations are. It might be a beginner limit, the site might have refused his upload and there's nothing the Mods can do. All I can do is ask.
 

bertus

Joined Apr 5, 2008
20,049
Hello,

As the TS has 13 posts made, he should have all the rights.
The pop-up of the "Upload a File" button will show you the allowed file-types.

Bertus
 

Thread Starter

nycokello

Joined Aug 10, 2009
35
Hello members,
First, thanks for your responses.
I'm using a phone, but I realized that it didn't upload the photo. I believe the photo is now there.
I cut off the upper part to make it do what I want...
 

Tonyr1084

Joined Sep 24, 2015
3,577
Is this a thermal (steam) vaporizer or is it an ultrasonic atomizer? You said atomizer, so I'm going with that. The way they work is they produce an ultrasonic shockwave at a specific frequency. That sound wave energy propagates through the standing water to the surface where the signal bounces back to the resonator (the piezo element). There's a sweet spot where atomization will be at its best.

When the sound wave strikes the surface it literally explodes the surface casting a very fine mist of water into the air. Typically a fan will blow the (lets call it) smoke up, out and into the room where it evaporates and thus, humidifies the room. If you change the voltage you MIGHT change the amplitude, but I'm more prone to bet that they don't like to operate at any frequency other than their designed size (diameter and thickness). If it IS an ultrasonic mist humidifier I don't know if you can adjust the amount of smoke coming out of it. You should be able to vary a fan that pushes the smoke up the tube (if it has a fan). The ones I have use a door that allows more or less air flow. What doesn't make it out of the tube collects inside the tube and drips back into the reservoir.

Now, if it's a steam humidifier, varying the amount of energy going into the heat element will either cause it to stop boiling the water (into steam) or if you're successful you MIGHT be able to get it to slow down a little. Those things, as far as I know, aren't designed to be variable in their output. They're either on or off. Only with the use of a door that can open or choke off the air flow in an ultrasonic type can be made to vary simply by opening or closing down the plastic vent flap. (aka, door)

But it looks like there's already a method for varying its output. That knob. Looks like it might vary the speed of a fan. Since you've cut down part of it - I can't begin to guess what is missing.
 

crutschow

Joined Mar 14, 2008
23,317
Without knowing how the pot works in the circuit it's difficult to recommend a way to control it externally (other than adding a stepper motor to physically rotate it).
 

Thread Starter

nycokello

Joined Aug 10, 2009
35
Is this a thermal (steam) vaporizer or is it an ultrasonic atomizer? You said atomizer, so I'm going with that. The way they work is they produce an ultrasonic shockwave at a specific frequency. That sound wave energy propagates through the standing water to the surface where the signal bounces back to the resonator (the piezo element). There's a sweet spot where atomization will be at its best.

When the sound wave strikes the surface it literally explodes the surface casting a very fine mist of water into the air. Typically a fan will blow the (lets call it) smoke up, out and into the room where it evaporates and thus, humidifies the room. If you change the voltage you MIGHT change the amplitude, but I'm more prone to bet that they don't like to operate at any frequency other than their designed size (diameter and thickness). If it IS an ultrasonic mist humidifier I don't know if you can adjust the amount of smoke coming out of it. You should be able to vary a fan that pushes the smoke up the tube (if it has a fan). The ones I have use a door that allows more or less air flow. What doesn't make it out of the tube collects inside the tube and drips back into the reservoir.

Now, if it's a steam humidifier, varying the amount of energy going into the heat element will either cause it to stop boiling the water (into steam) or if you're successful you MIGHT be able to get it to slow down a little. Those things, as far as I know, aren't designed to be variable in their output. They're either on or off. Only with the use of a door that can open or choke off the air flow in an ultrasonic type can be made to vary simply by opening or closing down the plastic vent flap. (aka, door)

But it looks like there's already a method for varying its output. That knob. Looks like it might vary the speed of a fan. Since you've cut down part of it - I can't begin to guess what is missing.
 

Thread Starter

nycokello

Joined Aug 10, 2009
35
Tonyr,
You are right.
This is an ultrasonic atomizer, made from China. It has an internal fan that blow out the mist.and they come out through the tube av added there. Of course the rate of mist production is controlled through the knob you are seeing ; and that knob is the 10K variable resistor I was talking about. I just wanted to automatically control it ;rather than the manual control. I can try linking the fan to PWM and see the outcome. av never thought of it, but I'm seeing it may work for me.
 

BobTPH

Joined Jun 5, 2013
2,021
The potentiometer is most likely wired one of two ways:

1. It is used as a potentiometer, giving a fraction of a fixed voltage on the outer terminals and outputting a fraction of that voltage on the slider to a high impedance input.

2. It is used as a variable resistor, varying the current into a lower impedance input.

If it is operated like case 1, you can simply replace the connection of the slider with a voltage source that can output the same range.

If is is case 2, it would be more difficult to do, but you might be able to get the same effect with a voltage source + a resistor.

I would look at the connections to the existing pot and measure the voltage on the slider to see how it is used.

Bob
 

Thread Starter

nycokello

Joined Aug 10, 2009
35
The potentiometer is most likely wired one of two ways:

1. It is used as a potentiometer, giving a fraction of a fixed voltage on the outer terminals and outputting a fraction of that voltage on the slider to a high impedance input.

2. It is used as a variable resistor, varying the current into a lower impedance input.

If it is operated like case 1, you can simply replace the connection of the slider with a voltage source that can output the same range.

If is is case 2, it would be more difficult to do, but you might be able to get the same effect with a voltage source + a resistor.

I would look at the connections to the existing pot and measure the voltage on the slider to see how it is used.

Bob
 

Thread Starter

nycokello

Joined Aug 10, 2009
35
Thanks Bob,
I think the potentiometer has been used as a variable resistor ; because only two of its terminals are connected.

Do you av a similar humidifier to help me check it... I'll be much grateful...
 

Thread Starter

nycokello

Joined Aug 10, 2009
35
The atomizer is being powered by 24V DC power supply.
Do you think using a variable power supply, let's say 12v to 24v can vary the rate of mist production ; without affecting it's oscillator?
 

KL7AJ

Joined Nov 4, 2008
2,208
Without knowing how the pot works in the circuit it's difficult to recommend a way to control it externally (other than adding a stepper motor to physically rotate it).
I was thinking that might be the most direct approach....especially considering parts procurement in Kenya (can't be much worse than
Alaska...LOL)
Eric
 

Thread Starter

nycokello

Joined Aug 10, 2009
35
Hello Eric,
I don't prefer mechanical devices because they are prone to failing!
I just need something that can last.

But, I'm grateful for your input...
 

Tonyr1084

Joined Sep 24, 2015
3,577
Like I mentioned before, I have a few ultrasonic humidifiers; however, I'm not prone to disassembling them to see how they work. In fact, I know I don't have a variable speed fan, I just have a variable opening to meter the amount of humidity that comes out. So I can only guess that the pot you have may be a wire wound type of pot. Capable of handling more current than the regular sort of carbon based pots which are very common. Unless they're using the pot to already control some sort of power supply to the fan, which is also entirely possible.

Can you take pictures of the guts? Since you're wanting to replace the mechanical dial with something controlled solely via electronic means, you should be able to open it and take a few pictures. If you can get some numbers off the actual pot - - - .

I'm thinking if it's electronically controlled then you might be able to replace the pot with a variable resistance IC, one designed for such work. However, I know they don't handle much current, so exactly how we proceed we need to know what we're working with first.
 
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