proportional valve control circuit help

Alec_t

Joined Sep 17, 2013
14,280
Can you confirm (a) you have the 24V version of the valve: not the 12V one and (b) your PWM signal is 12V amplitude: not 5V?
 

strantor

Joined Oct 3, 2010
6,782
Can you confirm (a) you have the 24V version of the valve: not the 12V one and (b) your PWM signal is 12V amplitude: not 5V?
Oh, good call. Once it was discovered the voltage signal didn't need to provide 10W of power, I thought the thread was done. Didn't realize we still had the issue of converting PWM to analog. I will see if I can find a signal conditioner that does this.
 

strantor

Joined Oct 3, 2010
6,782
You could roll your own based on this, and it would be a lot more accurate/faster than a filter. You would need to design a PCB with some opamps on it to get up over 18V output.
 

Thread Starter

woerr

Joined Apr 5, 2015
40
Sorry, I got no notifications that there have been new posts :(

I currently have the 24v version because it was the only one that was available, but my end product will be using the 12v version. control range will be 6v-9v.

The microchip I'm using is a chipkit Uc32, and changing pwm frequency is a bit complicated, and the PWM input im using is from a motor driver that will run a 12v dc motor up to 25A

The valve I'm using is from a local supplier that imports them. and since we are in the agricultural industry they will be tested extensively.
 

strantor

Joined Oct 3, 2010
6,782
The microchip I'm using is a chipkit Uc32, and changing pwm frequency is a bit complicated
So again I was pretty close LOL.

upload_2017-11-28_10-55-41.png


the PWM input im using is from a motor driver that will run a 12v dc motor up to 25A.
What do you mean the PWM input? And what's this motor controller got to do with it?
I thought you were talking from UC32 (arduino) via [some circuit you're trying to figure out] directly to the valve.
Where does the motor controller come in?

The more detail you provide, the better help you get. I've guessed a few of the details correctly but I shouldn't have to guess.

I currently have the 24v version because it was the only one that was available, but my end product will be using the 12v version. control range will be 6v-9v.
So you need to be able to adjust your output range from [12 to 18V] for testing, down to [6-9V] later for the real deal?
If so, you're going to need an opamp output with an adjustment pot.
I would recommend getting a proto-shield for your UC32 and on it build a circuit using the LT2645 and some opamps to amplify the output with a gain adjustable by board-mounted pot.
 

Thread Starter

woerr

Joined Apr 5, 2015
40
Im trying to provide all relavant info, but not always sure what is. So from my microcontroller the pwm goes to a dc motor driver that currently drives dc motors. So i want to add the option to drive hydraulic motors instead. So I was planning to be able to wire the motor output into this new circuit to get analogue voltage to control the valve, then just change my pid tunings in software.
 

strantor

Joined Oct 3, 2010
6,782
Im trying to provide all relavant info, but not always sure what is. So from my microcontroller the pwm goes to a dc motor driver that currently drives dc motors. So i want to add the option to drive hydraulic motors instead. So I was planning to be able to wire the motor output into this new circuit to get analogue voltage to control the valve, then just change my pid tunings in software.
That's the wrong way to go about it IMO.
The way it should be done is PWM directly from the micro goes [thru PWM>analog circuit] straight to the valve.
 

MaxHeadRoom

Joined Jul 18, 2013
28,621
Neutral on a proportional valve is usually off, and one extreme is full on, at least I took it that was the way I took Neutral to one extreme to indicate.
Max.
 

strantor

Joined Oct 3, 2010
6,782
He talking about 2 different valves and it's hard to know which one we're talking about at any given time.

The valve he has right now is 24v version so:
6v full flow A
12v neutral
18v full flow B

But the valve he's designing for is the 12v version so:
3v full flow A
6v neutral
9v full flow B

If he says the control range is 6-9v, to me that means between neutral and full flow B, on the valve he's designing for.
 

Thread Starter

woerr

Joined Apr 5, 2015
40
That's the wrong way to go about it IMO.
The way it should be done is PWM directly from the micro goes [thru PWM>analog circuit] straight to the valve.
The reason I am keen to do it this way is so that its very easy to switch to a dc motor if needed, the other reason is that the motor driver has built in opto-coupler, so my 12v and 5v circuits are isolated from each other.

He talking about 2 different valves and it's hard to know which one we're talking about at any given time.
If he says the control range is 6-9v, to me that means between neutral and full flow B, on the valve he's designing for.
This is correct, Forget about the 24v version, I am only working with the 12v version now.

I see it as a one-way proportional valve if he isn't using the lower range below neutral
Correct, The valve is a two directional proportional valve, but I am only using one direction. 6-9v
 

strantor

Joined Oct 3, 2010
6,782
The reason I am keen to do it this way is so that its very easy to switch to a dc motor if needed, the other reason is that the motor driver has built in opto-coupler, so my 12v and 5v circuits are isolated from each other.
I think You are talking about using the the actual motor power PWM output to the valve correct? Not some low power signal?

If so then your PWM out from the drive is probably not going to behave like you want. It is designed to have a motor connected and probably depends on motor back EMF to adjust duty cycle. With a valve connected it will probably behave erratically or not at all. Have you tried it yet? What is model # of the drive?
 

Thread Starter

woerr

Joined Apr 5, 2015
40
I think You are talking about using the the actual motor power PWM output to the valve correct? Not some low power signal?

If so then your PWM out from the drive is probably not going to behave like you want. It is designed to have a motor connected and probably depends on motor back EMF to adjust duty cycle. With a valve connected it will probably behave erratically or not at all. Have you tried it yet? What is model # of the drive?
I have tried it, all I needed to do was add a 2.3ke pull down resistor to the motor output and it behaves fine. I added the level shifting resistors and the two lc filters and my output looks great.

Am I correct when I say that if the valve needs no current from the signal wire that there is no need for the op amp in the circuit?
 

strantor

Joined Oct 3, 2010
6,782
I have tried it, all I needed to do was add a 2.3ke pull down resistor to the motor output and it behaves fine. I added the level shifting resistors and the two lc filters and my output looks great.

Am I correct when I say that if the valve needs no current from the signal wire that there is no need for the op amp in the circuit?
It is correct the valve needs no current.
I can't confirm about the opamp because I'm not positive what voltage you need (assuming 6-9V), I don't know what circuit you've chosen to convert PWM>analog, and I don't know what voltage you're getting out of the PWM>analog circuit.
 
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