Force a water pump to draw more current for a short period

Thread Starter

seanlin96

Joined Feb 3, 2019
16
I am trying to design a flushing system using a water pump rated at 10A running on a 12V battery (92Ah).

I have a current sensor which measures the current draw. The idea is once a partial blockage is detected, force the motor pump to operate with more power for a few seconds to flush out the blockage.

The pump is usually used for draining waste water, and when it is not blocked, it draws around 5A. Once a partial blockage is detected, the pump will draw around 6A, I want to increase the amperage to 8-9A to give it a sudden influx of power in attempt to flush out the blockage. I want to implement some circuit on the PCB shown below which can force the pump to draw more current.

Is it possible to force the motor to draw more current? If so, what chip or IC should I use?

upload_2019-6-18_15-40-20.png
 

WBahn

Joined Mar 31, 2012
24,693
Depending on the pump, the only way to force it to draw more current than it naturally does at full operating voltage is to increase the operating voltage above full operating voltage. Again depending on the pump, this could damage the pump, particularly if it has embedded electronics.

You probably do not want to force it to draw a specific amount of current -- that could result in pump overspeed and possible damage if your blockage isn't too much or clears right away. Instead, you probably want to determine a voltage level that will produce an acceptable surge while not being able to damage the pump under normal conditions. With that, you would then need to store enough charge in something like a capacitor to boost the voltage up for a short period of time.

There are other, probably better, routes to explore, too. For instance, imagine a spring-loaded piston that holds some fluid in it and is just downstream of the pump. When a blockage is detected, the piston is released giving a very sharp surge into the line. Once fired, circuitry simply pulls the piston back to reset it for the next time.
 

Kjeldgaard

Joined Apr 7, 2016
378
Motorized pumps can be some weird creatures.

Since the pump appears to be stalled, I doubt that an increased supply voltage will raise the flow.

But a few suggestions might be to stop/start the pump a few times to shake the dirt loose, or if the pump can run/pump backwards it could be another suggestion.
 

Dodgydave

Joined Jun 22, 2012
8,389
It would probably be better if it's blocked to pulse the pump forward and backwards to try and loosen the blockage, to force more power into it you need to raise the supply voltage.
 

MaxHeadRoom

Joined Jul 18, 2013
19,033
What is the nature of the pump, radial impeller, gear, vane?
The first one is common for sump pumps etc, and draws less current when blocked or restricted, the other two the opposite.
Max.
 

MisterBill2

Joined Jan 23, 2018
3,874
What is the nature of the pump, radial impeller, gear, vane?
The first one is common for sump pumps etc, and draws less current when blocked or restricted, the other two the opposite.
Max.
Never use a gear pump for waste pumping because a gear pump that is not worn has almost no clearance and so any solid obstruction will stop it or lead to serious damage. A vane pump is almost as poor a choice, unless it is one of those rubber flapper types.

And over-driving a motor in an attempt to clear a blockage may be OK for a SERIOUS EMERGENCY, if done manually intentionally, but to do it automaticly is heading for a disaster. Better to have the overload start a short timer that triggers a shutdown and sounds an alarm requesting human intervention. OR get a larger and more powerful waste pump.
 

MaxHeadRoom

Joined Jul 18, 2013
19,033
Never use a gear pump for waste pumping because a gear pump that is not worn has almost no clearance and so any solid obstruction will stop it or lead to serious damage. .
I was simply trying to ascertain the type of pump the OP is using, as if it is the common radial-vane type then the current drops with blockages on either the intake or outflow.
Max.
 
Interesting tidbits here. yep, high supply voltage for higher current then PWM at the average voltage of the normal supply.

The piston Idea I like. Air cylinder+compressor. We had a design that was never tested to try to clean heat exchanger tubes using a huge air cylinder. It was built, but never tested, and returned to the company.
 

drc_567

Joined Dec 29, 2008
711
... one additional physical principle involved in establishing an efficient drainage flow rate is to allow atmospheric air pressure to directly access the flow. Typically, this is accomplished by installing a vertical tube in the drain line, usually extending several feet, with a tee fitting, within 5 feet of the drain fixture.
... Known as a 'Vent to Roof' or 'Drain-Waste Vent', it works something like when you pour juice from a tin can, you punch one opening for the actual pouring, and an extra hole to allow air into the can.
... So, if the flow rate appears to be sluggish or reduced, you may want to consider adding a VTR.
 

Thread Starter

seanlin96

Joined Feb 3, 2019
16
There is no hint given that it is a sewerage type of drain, that is a guess that I made based on not much. And notice that we have not seen any more comment from the TS. Probably getting more information will lead to suggestions that are more likely to be useful. Just as in a large number of instances.
Hi, thanks for reply.

The pump is used to drain waste water from a tank. The waste water in the tank is from washing machines. So there can be clothes wool, hair and other small debris.
 

Thread Starter

seanlin96

Joined Feb 3, 2019
16
Thank you for all the replies, I have read through all comments.

As I understand the only way is to increase voltage or use some external hardware to provide impulse. As this is a university project, I have very limited budget, thus external hardware may require a lot more resource. If there are any more possible ways using firmware to provide the influx, will be greatly appreciated. I will also consult my professor for possible ideas.
 
I just built a sock filter holder for the washer. It's located in the wash tub under the discharge hose. The drain in the cement floor kept getting plugged.

It was an easy, elegant project in the end. I needed to borrow a lathe to make it elegant. In the proof of concept stage, emptying the filter wasn't ideal and I had to try different filter mediums.
 

MisterBill2

Joined Jan 23, 2018
3,874
Given the nature of washer discharge and having dealt with the resultant plugging issues, what you need to know is that the fiber build-ups are fairly mechanically strong and typically require manual removal because they continue to build once they start. The pumps that are self clearing have larger clearances and the ability to cut up any blockage types of materials. So if this is an engineering class project then it may be fair to ask if there is a solution. One possible solution could be a venturi arrangement with the velocity of the pumped fluid creating the flow to drag the fiber-containing material along. Since it would be draining from a tank the best solution will be a means to prevent the materials from entering the pump by using a screen type of filter for a secondary separation section.
 

jpanhalt

Joined Jan 18, 2008
7,894
I agree with KISS. When dealing with waste water from a washer, the best solution is to trap the lint before it goes into the drain. That is a must for septic systems and is also required in some municipalities. Lint filters (sock like) are widely and inexpensively available.
 
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