Hydraulic SYM

Before I can give you a brief basics introduction on how to use the oscilloscope, can you send a picture of the front and rear panel? What I am looking for something labelled either "Calibration" or "test" or something along those lines. This source will be crucial for a DIY basics intro.

If you don't have one of those sources then we can work around that with a tiny bit more effort.

It won't take you long at all to learn how to use the oscilloscope.

Cheers

Hi

See pics attached

Just to get you started:
http://web.mit.edu/6.101/www/reference/TDS3000Manual.pdf

This is a link to the manual, go to section 1-1 and finish at 1-3.

Doing this will ensure that the probes are reading correctly and if not, can be adjusted to correct reading.
The pictures make it easy to follow.

FOLLOW this initial procedure to ensure proper function of the oscilloscope.

What we will do here is use this known signal to learn how to use the oscilloscope for basic readings. We know that the signal is 1KHz at ~5v.
Your vertical/horizontal lines on the screen are referred to as "Divisions". Vertical being VOTLS and horizontal being TIME (in seconds).
For the purpose of this exercise we will not be using markers or cursors to do measurements.

On the face of the oscilloscope there are the two divided sections that independently control either vertical or the horizontal readings.

When using the AUTOSET button, the oscilloscope will automatically adjust all the setting to display the signal on screen. Sometimes the machine does not capture the full signal and so we can adjust things manually.

Play around with the following rotary knobs and see what happens with the 5V signal, if you get stuck and can't re aquire the singal just push the AUTOSET button to automatically get the signal back.

IMPORTANT:
The TRIGGER is what senses your waveform, if the trigger is not within the waveform the oscilloscope will look like it is having a fit.
After pressing the AUTOSET button, rotate the TRIGGER - LEVEL rotary knob and watch the display. You will see a thin, horizontal line appear on the screen and it will move up or down as you rotate the knob. You will notice that it is within the waveform. So it is not BELOW or ABOVE the wave but WITHIN the wave. As you manually change the SCALE of the VERTICAL divisions you need to make sure that the TRIGGER level stays WITHIN the waveform. Again play around with the trigger level and watch its effects on the reading as it goes ABOVE or BELOW the signal.

POSITION:
We will focus on the "VERTICAL" side of the controls.
This is where the ZERO will be, so where you take your readings from. When the Oscilloscope initially starts up the yellow line (Channel 1) should be in the center. If it is not you can move the line up or down to a division of your choosing, usually we pick the very middle line. To do this accurately connect the ground clip to the probes center to short out the probe, effectively grounding the probe to read "0V". There are other ways to do this but we'll keep things simple for now. You can change the POSITION of the HORIZONTAL component but we don't need to touch this yet at all.

SCALE:
The Oscilloscope has 10 divisions for both horizontal and vertical readings, from these we can measure the voltage/time of a signal by reading how many divisions the signal has taken up. Sometimes the signal will not fit within the divisions or may be too small to read. To compensate for this we can change the VALUE of those divisions. The picture that you have posted shows a reading in the bottom left saying "Ch1 1.00mv", this is telling you that the current setup is set to view channel 1, with each division having a value of 1 millivolt. Obviously this is too small to read a 5V signal so you can rotate the SCALE knob to change the value of channel 1 to about 2V per division. This means that for a 5V signal you will see the signal taking up 2.5 divisions. Alternately you can have the value of the channel to 1V per divisions but you will have to choose a lower ZERO level to fit within the 10 division display. So instead of having the ZERO on the center line you can choose ZERO to be one division below the center line.

I'll leave it here for now. Once you are happy with reading a VOLTAGE LEVEL we can move on to measuring the FREQUENCY component of the waveform.

THANK YOU M8

THANKS TO YOU AND A YOUTUBE VIDEO I NOW UNDERSTAND THE BASIC OPERATION OF THE OSCILLOSCOPE

MINE GIVES ME INDEED THE SQUARE WAVE AT 5V AND 1.005 KHZ

I DID NOTICE THAT THAT THE WAVE IS QUITE NOISY AT THE TOP EDGES AND THE RISING AND FALLING EDGES ARE VERY THIN..

IS THIS NORMAL?

NOw...

What do I need to do to measure the output of my atos valve?

Do I simply connect the probe in parallel with the two cores for the coil?

Another thing I would like to know is, what happens if I connect the probe directly to the 240v mains?

The ground to neutral and tip to phase?

My probe says it's 600v

Can I measure the wave and check the noise on the mains?

Finally, what do I need to watch out for in order to prevent me blowing up my expensive scope?

Thanks m8

Good to hear!

In regards to the noise of the calibration reading, can you take a picture? It is quite normal to have a bit of fuzziness on the readings when doing that specific test.
It all depends on just how fuzzy it is.

In terms of measuring mains voltage. Personally I would not attempt this.
Reason 1: I haven't done this myself so I cannot guide you here.
Reason 2: Possible damage to the oscilloscope if not done properly.
Your machine is a CAT 1, which means low voltage signals are the preference but it can read up to a max of 150V RMS.
If you have 240V AC mains then you will need to make sure that your probe is a CAT 2 (at least) and has a selector switch to go to a x10 or x100 reading.
These x10/x100 settings have resistor networks that bring the voltage down by a factor of 10/100. This means that when making a reading you need to multiply that reading by x10 or x100. This is done to bring high voltage signals down to a level where it will not destroy the oscilloscope. Usually if measuring mains there are CAT 2 and CAT 3 machines that you can directly plug in mains level voltages.

The solenoid.
You should be able to go across the coil BUT..... As long as the coil does not switch polarity like how a H-Bridge reverses a motor.
One way to test your output signal is to connect something like a 10k resistor to the output and put your probes on that.

Hiya

Yes, very cool indeed... I now know more than I did yesterday so it's great..

i will attach a picture of my measurement...

Now.. Went back on the simulator and tried the scope across the coils of the original Valve and OMG.. what a mess of noise.. can't make anything out of it so i decided to try another VEA250 which i have received and i managed to control the hydraulic..

I am attaching a link to a video of me doing it bellow..

This one also goes crazy hot and i only operate it for a couple minutes at the time to avowing it burning as well..

so i have attached a multimeter measuring the DC Current that the coil pulls whilst operating and I am ranging between 1.2A and 2.1A...

As previously pointed out by someone the VEA250 is rated at 0-1A output current, so is this solely my issue??

to have a smooth operation of the hydraulic with the VEA I had to fully turn the onboard pots to maximum ( DITHER, NULL and GAIN).
Anything else and it wouldn't work or would jitter


video for me operating one of the Hydraulics

I think that the only way to continue using the VEA250 is to try to add active cooling to the components that get hot. So basically a heat sink and a fan.

Going back to the oscilloscope, you would want to have the valve in a stationary position, I'm pretty sure that a PWM signal is sent out to the solenoid and if it is constantly changing the scope will have a hard time triggering on the signal. You would have to pre set the trigger level. What I am expecting you to see is a square wave similar to that wave that you saw while having the probe on the calibration source.
Only this time I expect that the voltage level is going to be 24V. So set your Volts/Div to 5V and have the 0 volt line down low on the display so that the waveform will fit over 5 divisions. Your trigger should then sit a few divisions above your 0 volt line. As you play around with the potentiometer to change the position of the valve, the wave form will either squish up or exand out along the TIME axis. What you are seeing here is not a change in frequency of the PWM but a change in the Duty Cycle. You can put your volt meter on this as well and see a DC voltage rise up and down as you change the position on the solenoid. What the volt meter is reading is the AVERAGE of the PWM.

You can think of PWM in this way:

Imagine a 12V LED light attached to a PWM signal. As the Duty cycle increases the light gets brighter, because all that the light sees is the Average DC component of the PWM wave. So even though the PWM would have a constant peak of 12V, the voltage level that the light sees is dependant on the Duty Cycle (On time VS off time) if the Duty Cycle is only %50 then the light effectively only sees 6V.
So a PWM signal will always be the same frequency, only the amount of time that the peak voltage is ON will change.

In addition to the PWM, you will see that the peaks of the wave will look like they are noisy. This is not noise that you see but DITHER. Dither is a small waveform injected on top of the PWM and makes the solenoid valve vibrate ever so slightly. It does this as I have explained earlier, to combat sticktion of the valve.

I hope I haven't lost you with any of this but it will come in time.

I have an idea for you. Get one of your arduinos (if you have one) and find the code that lets you DIM the onboard LED with a potentiometer. You can connect the oscilloscope to the positive side of the LED and read the PWM signal applied to the LED as well as using your DC volt meter to read the voltage that the LED sees.

Hi

This is what I got/..
19.8v...

Can't see changes...whilst adjusting the pot...

Very confused indeed...

Anyway, what really puzzles me is that if the VEA works then I must be doing something right...

Is there a controller in the market that I can just buy that does what this vea250 does but can take more current output?

Btw, my measurement was made whilst using the original valve controller and not with the VEA...

That measurement certainly looks like a PWM signal, you can tell by measuring the duration of the positive period of the wave vs the 0v period.
The picture you have shown also shows 50V !!

One thing to check on the oscilloscope is that it is not in single run mode. Single run mode is where the scope will take one measurement and lock that on the screen. Press the RUN/STOP button while the valve is moving and see what the wave does.

Is the valve moving as you adjust the pot?

Here is a video on what the PWM signal would look like as it changes.
The video is not mine.

Hiya

this is what i mean.. it's all over the place..

i will try again and make sure is not froze..

The 50v populated on the screen when i pushed the Measure button to snap the frequency and amplitude on CH1..

don't get it as is being fed with 24v


i am not using a pot with the original electronics.. the pot is being used with the VEA... the original electronics moves the valve by applying a 0-10v signal on the control pins of the atos.

say if i apply 5v to pin D an E it moves at speed x in one direction, if i invert the polarity between pin D and E it moves in the opposite direction and if i reduce and increase these 5v it moves faster or slower..


The same effect happens with the VEA but by the means of adjusting the pot on the board.. however with the VEA you know the problem...

I believe the coil is controlled by adjusting the current rather than the operating voltage... is there a ee a device that you aware that can help me with this?

Cheers

M

not sure if you had a chance to look at the spec sheet on the VEA250
http://ca01.smcworld.com/catalog/BEST-5-5-en/mpv/5-p0899-0901-vea_en/data/5-p0899-0901-vea_en.pdf

it says:

"Uses a P.W.M. (pulse width modulation) sys- tem to achieve an effective dither, thus mini- mizing hysteresis of the electro-pneumatic proportional valve."

Since to a point the VEA250 works, can we not find some other Controller i can purchase that works in the same way and get it over with?

I will try and shift the VEA250's 0n ebay or something if anyone is looking

I came accross http://pwmcontrols.com/PVD3D2R.pdf and

https://www.hydraforce.com/Electro/Elec-pdf/3-426-1.pdf


would any of these do the job?

Cheers m8

Hey,

That PVD3D2R controller looks like it could do the job. It even can control 2 valves, 3A each.

The other controller looks like it will only just makes requirements at 2A output.

I bought one... see what happens

@Marco Dias
I really hope you haven't bought yourself another white elephant.
If you look at the PVD32R datasheet, what mode are you going to use?
Then look at the wiring diagram and output curves.

You say there is only 2 wires connecting to the solenoid coil.
To me that is pretty stupid way of controlling the coil, if you look at most other bi-directional proportional valves they use 2 separate coils.
This is why I asked about your coil in my last post.
I think the only way your going to be able to use the pvd32r controller is if your solenoid coil is unipolar, ie. the coil is center tapped and tied to ground. Test it out by using your multimeter to test if there is resistance between one lead and the metal case.
If the test is true then MAYBE you can tie SolA- and SolB- together then connect SolA+ & SolB+ to the coil.

Myself, I haven't built a hydraulically controlled sim, so have decided not to comment . @Marco Dias - Keep up the good work in trying to find a solution .

End of project lads..

Gotta move so sim on ebay...


Hard to see it go but that's no other option, unless I find a large store quickly...

Thanks for yoursllyour help lads and my the force be with you

Cheers

Marco

hello,
that valve is a closed center 4 way 3 direction proportional valve, it is the best choice, because you can control the direction and speed, but you need an amplifier card to manage the speed, usually, the speed inputs can be between 0 and 5V or between 0 and 10 v, or between 4- and 20 mmA.
the same manufacturer of the valve sells the proportional card that is really expensive.