Need Low Volume Water Pump

[Noggin]

I have an idea for a project I'd like to build and I need a quiet low volume water pump. I have a friend that just went to college and she has a dehumidifyer in her room, and it fills with water every few hours and she has to empty it manually. So I had the idea to automatically detect the water and pump it out.

I first purchased a pump for an aquarium, but it doesn't seem to work well at all. I couldn't get it to pump water up a 6 inch tube, and this pump will need to raise a small column of water as much as 4 feet. I then thought that maybe a water pump for a liquid cooled PC would work, a quick look on newegg makes it look like I'm going to end up spending a few hundred bucks if I go that route.

Anyone have any ideas on where I can get a low volume pump? And I guess while I'm at it, I should ask if anyone has any ideas on how to detect distilled water reliably too I was thinking a floater switch would be best, I'm not even sure how deep the water pan is yet.

 

[dknguyen]

I think a floater would be best. You stick the float on the end of a rod with the other end hooked onto a rotary joint fixed to the wall of the tank (or just above it). YOu can use a rotary pot to detect the angle of the rod and hence the height of the float/water.

Not sure about the pump though...

 

[Noggin]

Oooo... a pot, thats even better. I was thinking of trying to get it to trigger a switch. I'm gonna be using a micro to time everything anyways, and it'll have an ADC on board.

A pump used in something like **broken link removed** might work fine.... I just don't know if it would be up to the task of pumping water up a small line the height of a counter.

 

[HarveyH42]

https://www.allelectronics.com/index.html
https://www.sciplus.com/index.cfm
**broken link removed**

Try these for pumps. They usually have several to choose from, 10-20 dollar range. Should note that fountain pumps aren't always self priming, although drilling a small hole can help air escape in some cases.

Had a similar problem a couple of years ago, huricane damaged the roof on my florida room. Wasn't a bad leak, but had to keep emptying the bucket. Had a lot to do, and that roof need to wait. Built the attached circuit to control the pump from my old boat. Worked fine, a little glitchy during thunderstorms. Sometimes it would turn on when the power fluxuated, no big deal, its on a timer...

Should note, I ran this off a breadboard, and messed around some trying to smooth out the power flux issue. This is the starting point, you may need to tweak it a little. Probably get a list of improvements from other readers, I'm not an engineer...

 

[Nigel Goodwin]

Don't try and get too complicated - the dehumidifier will already have a float to detect the water level, you could use that. Or, even simpler, most dehumidifiers have a drain connection (or could easily have one added), try and arrange it so it can simply drain by gravity.

 

[Hero999]

What about an old washing machine pump?

You might be able to pick one up for free at the local tip.

 

[HarveyH42]

Noticed after posting, my attachment didn't take, fix it. Should mention that I used two separate power supplies, the pump I used was high current, figured it would fry the control circuit.

 

[HarveyH42]

Windshield washer replacement pumps are only a few dollars, but not sure how quiet...

 

[Analog]

Here's one that'll lift up to 25 ft. for $19.99:

https://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=45019

may be overkill though.

 

[Noggin]

Thanks for all the suggestions guys, I think I'm gonna go with this pump:
https://www.goldmine-elec-products.com/prodinfo.asp?number=G15563

Its small and its cheap. I don't know how large the condensation pan is, but this one might actually fit in there. If it doesn't, then I'll have to hook it up outside of the pan. Hopefully just because its submersible it doesn't mean that it has to be submersed.... and if not, hopefully its also self priming.

 

[Hero999]

Hopefully just because its submersible it doesn't mean that it has to be submersed.... and if not, hopefully its also self priming.

It probably does need to be submersed becuase there probably isn't a connection for the intake hose and it probably isn't self-priming.

 

[dknguyen]

Don't try and get too complicated - the dehumidifier will already have a float to detect the water level, you could use that. Or, even simpler, most dehumidifiers have a drain connection (or could easily have one added), try and arrange it so it can simply drain by gravity.

All the easier to stick a rotary pot. I just know my humidifier has something like that, except it uses it to a roll a cylinder where 1/3 is labelled empty and the other 1/3 is labelled full (the last 1/3 is attached to the rod).

 

[philba]

I solved this almost exact problem. Wish I could have used gravity - I had intended to. I have a room that I maintain at 55F and the guys that installed the drain line ran it up above the intake before they ran it down. of course, it's behind siding so I had to pump the condensate out or rip the siding off the walls and replace it. sigh.

I use 3 stainless steel probes - one to ground the other 2 inputs to comparators. The probes + resistors form a divider which triggers the comparators. when the high probe senses water, it turns the pump relay on, when the low probe senses no water, it turns the pump off. I use a PIC and do a time-out in a couple of minutes to prevent burning out the pump in the case of failure. I also log the time and duration plus flash LEDs in certain circumstances (like time outs and a heart-beat). I decided not to use a float or pot because it's a condensing environment. I used #10 stainless steel bolts for the probes and a hacked up plastic box for the holder so I could adjust the depth. Works pretty well.

ps - is there any way to turn off avatars so I don't have to look at them?

 

[dknguyen]

ps - is there any way to turn off avatars so I don't have to look at them?

User CP>Edit Options>Thread Display Options>Visible Post Elements

 

[Noggin]

Ok well I talked to Devan, I'm gonna go up to see her on Wednesday and take a look at her dehumidifier. The catch pan is about a foot deep, so there will be plenty of room for the pump. I'm going to make the device with an Atmel microcontroller and run for a set time limit. I thought about using probes, but wasn't sure how well they'd work considering that the water would be mostly condensation. Thought about telling her to put some salt in the pan, but decided that ultimately that'd be a bad idea. I'm just gonna go with the floater thats already in there and run for a set time limit.

Next step is to figure out how to get a tube out of the catch pan, she said there's barely any gap.

 

[philba]

Ok well I talked to Devan, I'm gonna go up to see her on Wednesday and take a look at her dehumidifier. The catch pan is about a foot deep, so there will be plenty of room for the pump. I'm going to make the device with an Atmel microcontroller and run for a set time limit. I thought about using probes, but wasn't sure how well they'd work considering that the water would be mostly condensation. Thought about telling her to put some salt in the pan, but decided that ultimately that'd be a bad idea. I'm just gonna go with the floater thats already in there and run for a set time limit.

Next step is to figure out how to get a tube out of the catch pan, she said there's barely any gap.

the condensation has a moderately high resistance - around 100K, iirc. I mis-remembered the circuit - one probe (the lowest) goes to 5V and the other two form the high sides of 2 voltage dividers. the lower resistors are 200K to gnd. With no water, the comparators in the PIC see 0V, with water, they see around 3.2V. The reference input to the comparators is about 1.6V. this will work for water resistance up to 400K. I have had no problems on that front. Getting a pump to work in the shallow pan has been an issue - I wound up with a 12V windshield washer pump. works pretty well. the little giant submersables sucked...

 

[Hero999]

Yes, the condensation will conduct to some degree as it willl be weakly ionic due to the gasses from the air (CO2 and suplher and nitrogen dioxides) disolved in it.

 

[Noggin]

Well I saw the floater in the dehumidifier. Unfortunately, when the floater rises the switch extends and holds the floater in the upright position. So even if you pump the water out then the floater will still be upright. But, I think I thought of another way to detect the water level that I think will be fun

- Fairly strong magnet, I have many many neodymiums at work I can get
- PVC pipe
- small watertight bottle
- 2 magnetic reed switches. Can get these from work too and they're sealed if I remember correctly.

1. Attach magnetic reed switches to sides of PVC pipe, one high up and one low down
2. Insert magnet into sealed bottle
3. Put bottle in PVC pipe
4. Place PVC pipe vertically in water container

When the top reed switch closes, pump turns on. When bottom switch closes, pump turns off. This whole system could probably be controlled by adding a few other relays to control power... but she'd hate me if I did something stupid and filled her dorm room with water. So, I plan on still using the micro and use a current sense resistor.

I'm guessing (though I plan 100% on measuring several times to be sure I'm right) that the following is true:
1. If the pump is pumping ONLY air, current will be very low. Micro shuts off pump
2. If the pump is pumping water through the tube that slips off the counter onto the ground, current will be low (though not as low as pumping air)
3. If the pump is pumping water through an upright tube 4' high, then the current will rise as the water height rises.

So, if the micro doesn't see the current increase to a certain level, then it will shut off. Any comments?

 

[HarveyH42]

I posted a simple 555 monostable circuit, which I used for a while. I hot glued a hollow plastic ball to the end of a metal rod. Hot glued a scrap of wood to the side of the pan, and the plastic tube from an old pen for the rod to side up and down. Cut the rod of so that it was about three inches short than the pen tube. Mounted a lever microswitch over the tube to trigger the timer.
Personally, I think you are really over complicating this thing. But then again, there is a woman involved...

 

[philba]

I agree, seems overly complex with several points of failure. moving parts are going to be a problem area for any system that is expected to work long term (as in "forever"). especially home-made ones. gunk happens.

while my stainless steel sensors probably aren't 100% trouble free, they have been working just fine for quite a while. I just went and checked the resistance between 2 of the probes in the water in the catch pan and it was 121K. pretty stable over 12 months of use.