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Topic: Motor Control for Ulka Pump: What relay to use for phase angle controller? (Read 3294 times) previous topic - next topic


HI. Just getting into Arduino fun as I have joined the ranks of Roncilio Silvia espresso machine tweakers.  My Arduino Uno is on the way and I am making plans for my control circuitry.

I know it is overkill but I want to control the speed of the ULKA-EP5 vibratory pump. The idea is basically to slowly ramp up the speed for pre-infusion and gain concise control of the pressure over the whole range of the shot process. The pump It is 120VAC and draws 41 Watts.

My research has led me to believe that phase angle control is the best way to limit the current to this little motor without toasting it in the long run.

I found this nice zero cross detection(ZCD) board: http://www.mlgp-llc.com/arduino/public/arduino-pcb.html  and it seems the code will be pretty easy with a timed delay of the output based on the input signals from the ZCD board.

I am looking for suggestions on a relay to drive the motor.  Will a standard SSR work okay or do I need something faster or with some sort of snubbing? Any help appreciated.


Most AC SSRs are zero-cross types, which will not work in this application. A random-fire AC SSR should be OK. Alternatively, this opto-triac http://uk.farnell.com/vishay/vo2223-x001/phototriac-power-dip-8-0-9a/dp/1870800 should be OK for the job, it's rated at 0.9A.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.


Is there any advantage of a random-on SSR over a triac? I was considering a SSR like this: http://www.alliedelec.com/search/productdetail.aspx?SKU=70131485.  Would that triac you linked be able to hold up to 120VAC?


Either will work. However, that SSR has greater physical separation between the input and output, and a higher current rating. So I suggest you use the SSR.
Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.


What is man's best friend? The breadboard!


I am not sure that you can productively control the speed of a vibratory pump.

The diaphram that you are pushing and pulling to propel the fluid is going to have
its own prefered mechanical resonant frequency based on its own stiffness and
whatever springs it has connected to it,   and unlikely to work efficiently at
other frequencies.


I understand your concern, but I will not be changing the frequency as much as the power supplied during that frequency.  I think that with this method I will be varying how far the piston is pulled back during the cycle thus changing how much water is pumped every cycle.

The fact that the vibratory pump is frequency dependent s exactly why I intend to use phase angle control. 


I'm about to embark on this exact same project.  Did you have any luck, Constant5?

Can anybody see anything wrong with me simply following the directions below?http://playground.arduino.cc/Code/ACPhaseControl

It seems to me that a diaphragm pump is hard to drive at different speeds because it is engineered to rely on a resonance that results at a certain force and frequency of pumps, and changing either has a chance of preventing that resonance from being achieved.  Does anyone think that maybe just lowering the voltage going to the pump with a digital pot is a better idea that phase angle control in this case?

Maybe I should just ditch the vibe pump in favor of a rotary vane or gear pump on an AC motor?  It would be expensive to do, but I think I would be able to much better control their speeds.  Maybe that is a worst case scenario option.

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