PTS Flowbench Forum

Tony, yes I noticed the power levels effect the motor flow very noticeably, when a 5hp phase converter was running earlier today the motors were pulling less air, good to find out now rather than later!

I know a person that has been running 4 different vacuum motors from one of these controllers with a substantial heat sink and up to 35" no problem, they are inexpensive to buy on ebay.de I like german electronics

Yes you are right the potentiometer does have power going through there and it is Not advisable to touch the pot wiring or body!

One thing I found is that the pot turns significantly before the motors just start to turn, probably over 1/8 turn, indicating the 470K resistance may be a little larger than needed, the sensitivity is a little too sharp even when adjusting 2 motors so I am thinking 1 x 50K and 2 x 200K pots wired in series would be a better combination for fine adjustment yet being able to adjust the motor speed quite quickly when needed with less than 1 turn each pot from 0 to full power, I also like the idea of a 16A breaker rocker switch feeding the controller and a pressure switch to cut power to the motors if the bench reaches say 38" or 39" to save the DM and a switch having to be pressed to turn the motors on again

I am testing with the controller at full power just to make sure there is minimal difference vs when I have the new bench running

Out of interest can the automatic motor control be used with this type of power controller if I was using 2 or 3 of them?

I remember seeing a bench from Finland on here that was using 3 of them and automatic vacuum control but not sure how he has done this

Bruce, that is excellent! even better than I was thinking

In that case I believe 1 x 350CFM @16" orifice will do the trick and a few 28" calibration plates to suit, maybe 280, 200, 100 @28" which should cover everything I need

That is super handy not having to change the internal orifice plate, that alone is a Big plus point for the DM

With all of that in mind it is almost cheaper (and certainly easier) to use your DM and 3 or 4 orifice plates vs someone making manometers and needing a lot more orifice plates + having to regularly change them to keep the inclined manometer above 50%, the DM makes a Lot of sense

Keep in mind you have to run the internal plate 25cfm high than your max cfm testing point. You can not read a 350 plate using a 350 internal plate.

The current production PTS DM is now capable of about 38-39" of depression, the old one would top out around 35.5" and I have also now changed channel 3 (PT3) to a 100" sensor so no worry of maxing out the FPS. I had a few setup with the 100" on PT3 in the past for some customers and figured it would be a good upgrade to do on all production models now.

rwdford wrote: One thing I found is that the pot turns significantly before the motors just start to turn, probably over 1/8 turn, indicating the 470K resistance may be a little larger than needed, the sensitivity is a little too sharp even when adjusting 2 motors

The best solution to the sensitivity problem is fitting a ten turn potentiometer.
These are difficult to come by in values as high as 500K, but someone here at the Forum did discover a source of suitable 500K ten turn potentiometers, and its a good solution.
Fitting a larger diameter knob also helps a lot.

There are a few problems with any phase contol system. The first being that the motors typically require about 15v to 20v before they will begin to turn. So the first bit of potentiometer rotation nothing happens.
The other problem, especially with simple low cost modules such as the Kemo, is they just use a resistor/capacitor timing circuit to set the phase control timing range.
Any phase control system becomes erratic at the extreme ends of operation around the mains zero crossing points. So the range of adjustment MUST be deliberately limited to something less than 0% to 100% control range.
That, and component tolerances mean that a Kemo module might only go up to 92% or 95% or something (?) maximum, to keep out of the erratic triggering range right at the very top.

The more expensive phase control modules (such as those supplied by Bruce) use a microcontroller to set the firing angle.
The software is smart enough to allow full range adjustment from maybe 1% to 99% and its very linear in operation and reliable, and the control inputs are fully mains isolated.
Its also a lot more expensive than the Kemo, but also capable of a lot higher power.

I also like the idea of a 16A breaker rocker switch feeding the controller and a pressure switch to cut power to the motors if the bench reaches say 38" or 39" to save the DM and a switch having to be pressed to turn the motors on again.

That is a good idea for any flow bench where blocked flow can suddenly increase the pressure to dangerous levels.
It depends on the characteristics of the air blower, some hardly change pressure at all, others can spike incredibly high if flow is blocked.

Out of interest can the automatic motor control be used with this type of power controller if I was using 2 or 3 of them?

Kemo can supply an isolation module which replaces the potentiometer, and provides a fully isolated dc control voltage input to the Kemo power module. The automatic pressure control system can then be connected to the input of this isolation module. Its been done before, and definitely works.

I remember seeing a bench from Finland on here that was using 3 of them and automatic vacuum control but not sure how he has done this

He would have used three Kemo isolation modules, and three Kemo power modules to run three groups of motors off each of three phases.
There are now several three phase benches in operation around the world, and as far as I know, all have the automatic test pressure controller.

That is great Bruce about the 100" PT3, this will be useful for me, I reached over 60" before when testing carb main jet vacuum signal, it is quite useful to be able to test the PT3 up to 100" and makes the 40" DM even better


About the Kemo controller the voltage drop is 8 to 9V vs mains power, I was able to get 44.2" with a 35mm ID orifice straight mains power and a few seconds later I got 43.8" with the Kemo controller @100%, not a huge difference really

What I also noticed is that the mains power effected the max vacuum through the 35mm ID orifice from 43.8" to 46" daytime vs nighttime

The motors start to buzz at 15V

A 10 turn pot could work quite well, I have some pots here and large knobs so I will try them first and see how it goes

To remove the dead spot I could possibly use pot's that add up to a resistance that will not fully stop the motors from turning with the pots sitting at zero and then use a trim pot to fine tune the max resistance making the pot's work over almost the full scale, 95%+ instead of 65%

The PTS speed controller sounds best, I did not realise it will work with 230V to 240V 50Hz

I am happy with the Kemo controller so far, will know more about how well it works when using a low resistance 50 or 100K pot for setting the vacuum level

Thank you very much Bruce and Tony for your detailed responses

This is a Great forum!

Hello rwdford

I have also kemo modules my pts setup. I use stereo pot lin type but now i think log type maybe can also work. 500 kohm and 100kohm serial connect is my current setup.
http://www.newoldsounds.com/index.php?m ... s_id=10752

rwdford wrote: The PTS speed controller sounds best, I did not realise it will work with 230V to 240V 50Hz

The PTS speed control power module works with either 50Hz or 60Hz (switch selectabe).
It the requires a small mains powered transformer to provide it with 24 volts ac.
The primary of that transformer can be any voltage, whatever the mains voltage in your particular country is.
With a suitably rated random fire SCR and heatsink fitted, it could then control over a hundred amps worth of motors.

Your Kemo power module will work fine, provided you keep within the max power rating and use a sufficiently large heat sink with it.
Eight to nine volts loss at full output is not too bad. Some are known to drop a bit more than that.

Another toy to play around with might be a mechanical reduction gear on the potentiometer shaft.
Google "vernier reduction drive"
These most commonly have 6:1 ratio are very smooth without any slop or backlash, they cost no more than a potentiometer and are available on e-bay.

Like this Tony
http://www.orenelliottproducts.com/n50.html

That one is built into the variable capacitor.
But you can buy the very same friction ball reduction drive as a completely independent part.

This one advertised on e-bay right now is a genuine replacement spare part for a specific very popular piece of Ham Radio quipment, that price is for two of them.
Its the exact type of thing.

http://www.ebay.com/itm/YAESU-FT-101-RA ... 4150f082e0

They come up all the time on e-bay.

Interesting ideas again guys

After some experimenting I found 300K total to the controller feeds 30V to the motors, using a 200K pot and 100K pot for 2 motors the 100K pot seems perfect for fine adjustment of 2 motors

I will experiment with other pots but I think a 20K pot would be ideal for fine adjustment of 6 to 8 motors, I tried a 10K pot and it was much too fine for controlling 2 motors, probably 1" vacuum total adjustment

Using a combination of 3 pots will work best for me as a simple solution, I like the 6 turn gear reducer and may also test one of those

With the controller there is a cut off point at the low end as Tony was saying, at a certain resistance the controller shuts off the power to the motors, still working out what this cut off point is in ohms but ideally the pot's total resistance should add up to 15 or 20K more than this cut off point to gain best accuracy of the pot's


One thing I am wondering about is if I wanted to control 3 of these power units could I use the pot return wire from one of the controllers and feed it into all 3? or if not how can I adjust the motor speed of 3 controllers with a single pot wire?

I think I can get away with using 2 controllers for 6 motors but using 3 controllers would keep well within its max amps and room for more motors later on if needed


The power going to the pot is close to full mains power and the pot is used as a simple 2 wire variable resistor with a return feed

Do you think I could use one common return feed for 3 controllers?

I imagine the controller is just sensing the voltage difference each side of the pot but i am not sure if this will work, another option could be to use a mains power feed with a resistor to reduce the max volts a little and use this as the pot wire for the 3 controllers

To test I could use 2 controllers to power 1 motor each, I have a few spare controllers so no worries