Ideal AB Module for pulse control of a dosing pump

[mikebon111 0]

Hello All I just like to start by saying that I’m an operator, not automation guy so I apologize in advance if my questions aren’t very clear. I’m responsible for water treatment here at my power plant and I want to do some upgrades, one of which is automating my chlorine injection pumps. For next year I budgeted to have a pro come and do the upgrades but I have some funds leftover in this year’s budget that I’d like to use to get some of the needed hardware. The PLC is an AB SLC 5/04 and the pump is a ProMinent beta4, below is a clip from the pump spec sheet. Controlling contact (pulse): With voltage free contact or with semiconductor sink logic control (NPN), not source logic (PNP). With a residual voltage of <700 mV, the contact load is approximately 0.5 mA at +5 VDC. (Note: Semiconductor contacts that require >700 mV across a closed contact should not be used.) Pump ignores contacts exceeding maximum input rate, and will not remember. Necessary contact duration: 20 ms I have some available channels on a Relay Output Module (1746-OW16) that I think can be used for this but I’m not sure. My Question is: Will the 1746-OW16 module work for this application, if not which type module would be ideal? I have the module spec sheet but I can’t make much sense of what I’m looking at. Ive attached the spec sheet for the module in question Any advice will be greatly appreciated. Thank you AB PLC.pdf

[sthompson 3]

Welcome to the Forum! If you need a Contact Closure, I would recommend the 1746-OX8, which has 8 Isolated Contacts. Stu....

[JRoss 84]

A relay output is pretty universal, and can handle a large variety of devices, so in general the answer is yes. HOWEVER, from reading the somewhat confusing clip from the pump spec, it sounds the pump is controlled with a pulse train. If that's the case, you probably do not want to use a relay output because a pulse train will wear it out. Could you confirm how the pump is to be controlled? Is it just an off/on control? Could you, for example, wire it to a light-switch to turn it on and off manually?

[drforsythe 15]

Does this pump require a single pulse to make it work, or will you create a series of pulses in order to get the right amount of chlorine? If you have to turn on the output multiple times per second or with high frequency, an electronic output would be preferred. Can you give more details on what is required for the injection pump?

[mikebon111 0]

Thank you very much.. Sorry it took so long to respond...I didnt get anything in my email like I do with other forums...I figured that nobody responded...

[mikebon111 0]

Thank you for the response...I didnt realize that anybody had responded or I would have got back sooner... The way I understand it is...The pump will be plugged into an energized receptical with the pump speed set at 100% (With no pulse control the pump will be on pumping at 100% speed). When the pump receives the 20ms pulse through a control cable a relay in the pump to close which pauses the pump...I think...Right now the pumps on/off is automaticly controlled by the PLC through a relay...The 120v contact closes and the pump comes on...The pumps were recently moved outside onto the tank containment...So when operators are inside the water treatment building and see on the PLC that they need to increase the PH or something they have to go outside and make the adjustment then back inside to see the results. The first objective is to allow the operator to increase or decrease the pump speed from the panelview and eventually have the pumps controlled automaticly from the PLC...PH, Chlorine, Bisulfite....Does this picture help at all? Edited 29 Nov 2012 by mikebon111

[mikebon111 0]

Thanks for the response, sorry for the delay, I didnt realize that anybody had responded... At 100% speed the pump will pulse 180 times per min. We generally run at less then 50% speed so maybe 3 pulses every two seconds or so... Id like to have the ability to enter 20% on the panelview and have the PLC make the adjustment to 20% speed however many pulses it takes... Thank you Edited 29 Nov 2012 by mikebon111