Water full level Indicator

[transistor495]

Hi all.

There's a requirement in my home -a simple water level indicator. I wanna make it for my father to get informed when the watertank is getting full level. Now he's going through the ladder to the top of the house to see the status and feels difficult.

The switchboard is installed inside house and it'll be good to give an indicator there itself. My plan is to install the circuit on the top tank and power it using dc cable from downside ac adapter. Total length will be 20mtrs. So to give the indicator in downside itself, I need an extra cable feed from top making 3 wires!

I'm thinking about implement it using 555 or something like that on top to detect the water level and generate a trigger pulse and feed it via the dc cable itself and extract it downside and activate a 4017 to produce beep+visual. Is this practical for a 40KHz pulse and how can I do it.

Please put your ideas on this stuff. Not planning on commercial stuff

 

[MikeMl]

Biggest issue is a reliable, waterproof, corrosion proof sensor. A float arm with an embedded permanent magnet and a hermitically-sealed magnetically-actuated reed switch would be my choice.

If I was in a hurry, **broken link removed**, rather than make my own.

 

[crutschow]

A non-switch way to detecting the level is to use a water-proof thermistor. You apply enough voltage to cause it to self-heat significantly above the ambient temperature. When it becomes immersed in water its temperature will drop, changing the thermistor resistance and thus its current. You monitor the current to determine its resistance. This can be done with just two wires to the tank.

You could use a comparator/op amp to detect the voltage across a resistor in series with the thermistor and select the trip point to change its output state at the desired thermistor current. The comparator output can drive an indicator/buzzer as desired.

 

[Reloadron]

Read through this thread to see what crutschow is getting at. Especially the recent entries to the thread. There are also links in there to exact NTC thermistors used for level detection as to the level is there os not.

I can't see your setup but another trick is to get a pressure sensor switch out of a washing machine. The one where you set the water level in an upright machine. Those switches can be tweaked for all sorts of applications like you have.

Ron

 

[JimB]

Or, you could do as MikeML and use a sealed magnetic float switch.

Two wire connection up to the tank, just connect the switch and a lamp in series and connect to a simple power supply.

Job done!

JimB

 

[wannaBinventor]

Or, you could do as MikeML and use a sealed magnetic float switch.

Two wire connection up to the tank, just connect the switch and a lamp in series and connect to a simple power supply.

Job done!

JimB

This is more or less what Forest Mimms shows in some of his books. You want to use low voltages of course, and please be cautious and do research if a human being comes in contact with this water, but I wouldn't think it would be an issue at 5 volts.

 

[Hashime]

If you had an old toilet kicking around, the float from there can create enough force to push a physical switch if you wanted something really quick and dirty. You could just place a switch at the base holding the circuit open, and when the water level lifts the float, well, you know what happens.

 

[SABorn]

The little float switches are avaliable off Fleabay cheaply, think Sureelectronics had them or Virtual Village, it would save a lot of messing around and also be a reliable system.

Wires in water always fail with time as the plastic coating on wires will assorb water over time.

I have used many of the washing machine sensors that was mentioned above with good success.

Another way is a weighted float attached to a piece of cord that runs over a small pulley at the top, with a weight on the outside travelling inside a plastic pipe, you have a switch mounted in the plastic pipe the weight can activate.

 

[Boncuk]

I guess using a pressure switch salvaged from a laundry washer will offer two kinds of measurement.

Laundry washers operate with different water levels (heights) for washing and rinsing, with the water level higher for rinsing.

That way you could have two indications: the first when the tank is almost full and the other one when it's completely filled.

Boncuk

 

[awright]

While I appreciate the desire to accomplish this task electronically, I think your cheapest and best bet is to use a simple pressure gauge connected to your houshold plumbing. I am assuming that your system is not pressurized, but is a simple gravity system. A pressurized system could still use this principle, but sensitivity of the gauge display to water level would be reduced.

You don't mention the elevation or height of the tank, but if we assume the tank is 15 ft. above your kitchen fixtures and the top of the tank is 20 ft. above the fixtures, a gauge plumbed in at the fixture level would read 6.9 PSI with the tank empty and 9.2 PSI with the tank full (with no water being drawn). In this case a 10 PSI gauge with a couple of hash marks painted on the gauge face would provide adequate resolution to show the level in tank. Cost: from about US$10 up, depending on how fancy a gauge you want plus a few plumbing fixtures.

Note that this will provide a reading on the actual level of water in the tank, not just at a few instrumented positions. If you need an alarm or an automatic pump cutoff at full, a float switch is an ideal device. Just yesterday I purchased a new polypropylene float switch of the type mentioned by JimB from Grainge.com, a major industrial equipment supplier in the U.S., for US$12 to turn on a pump emptying a bucket catching rain leakage through a roof in a workshop. Most of these float switches can be changed from open on float rise to close on float rise by simply reversing the orientation of the float on the shaft. Depending upon pump current draw, you would probably have to add an electromechanical or solid-state relay or a semiconductor switch because the float switch typically can only drive a 30 VA (volt-amp) load.

awright

 

[bryan1]

No matter the input source whether it is mains pressure or gravity fed the easiest way to to do this is simply buy a float switch thats used on water troughs in the agricultural game . The float can be adjusted to suit the level drop and if say you wanted a 1/2 empty tank make a longer rod and bend it to suit provided one has the space to do it in the tank A fail safe arrangement and damn cheap too.....

 

[transistor495]

Wow!...I just got amazed one the number of wonderful replies I received within this short time

Actually till now I hadn't thought of a float-switch mechanism but a great idea! I'll chek if I can get one from market

I like the thermistor one too, but a question to cruts: Will it be reliable on a varying water temperature as the tank is open to climate changes?

To awright: The tank is on bit high elevation about 30+fts of a double storied building. Piston pump is used to pump water from a 150meters distant open well down the valley.

To JimB: What will be the output if we do it using a simple series float-switch like you suggested? The water level will be fluctuating at trigger point because of the falling water and it'll make a intermittent and annoying output? That's the reason I thought of using a monostable or bistable setup. This is my assumption and reply back your thoughts on it.

Once again thanks to all. It definitely improved my knowledge on this stuff.

 

[crutschow]

I like the thermistor one too, but a question to cruts: Will it be reliable on a varying water temperature as the tank is open to climate changes?

That's a valid concern.

It depends upon the ambient temperature range. For say a 32-100F (0-38C) change you could put enough current through the thermistor to self-heat 40C above ambient. Then even if the temperature is freezing, the thermistor will still be above a 38C trip point.

If the ambient temperature change is more than that, then you may need to add a second thermistor exposed to ambient air with both of them having sufficient current through them to self-heat perhaps 10-20C above ambient. The two thermistors are put in a bridge circuit. When the one becomes immersed it will change resistance relative to the other and unbalance the bridge. This can be detected with a comparator such as an LM339.

Edit: There is a flaw in this design. If the air cooled down so that is was 10-20C below the temperature of the water than you may not get an indication of the water being full. Do you have any idea of of what the relative temperature between the water and air may be?

 

[Jaguarjoe]

Gems has many float switches.

You can get free samples which makes them extremely affordable too!

**broken link removed**

 

[kinarfi]

real cheap and real dirty, but it sounds like it's far from potable water any way, is two bare leads in the tank that when the water gets that high, it conducts and turns on a FET or a transistor to turn on the light or relay and it is not allowed to turn off until the level drops to a certain level.
Kinarfi

 

[JimB]

To JimB: What will be the output if we do it using a simple series float-switch like you suggested? The water level will be fluctuating at trigger point because of the falling water and it'll make a intermittent and annoying output? That's the reason I thought of using a monostable or bistable setup. This is my assumption and reply back your thoughts on it.

As per the attachment.
Just a simple indicator lamp which illuminates when the water level is high.
Or you could use a bell or buzzer in parallel with the lamp if you want an audible alarm.

Power supply output voltage to suit the lamp/buzzer.

How is the water pumped?
Using an electric motor?

If you wanted, you could use two level switches and have automatic stop/start control of the electric pump.

JimB

 

[Jaguarjoe]

I think he wants hysteresis to prevent blinking/beeping alarms as the float bobs up and down at the trip point.

 

[transistor495]

To cruts: The air temperature range in my area is 10C-35C during all seasons. Chance out there that the water temperature goes ~10C below the air during day time. On the other way around it won't be more than a couple of C if ever happens.

To JimB: The pump is operated using electric motor. What I meant is the problem described by Jaguarjoe.

 

[crutschow]

To get hysteresis action with a float you could do something like on some sump pumps. The have a float on a sliding vertical rod. There are two clips on the rod to turn a switch on and off. The lower clip turns the switch on and the upper clip turns the switch off. The distance between the clips determines the hysteresis level distance of the water. Here are some commercially available.

 

[Reloadron]

To cruts: The air temperature range in my area is 10C-35C during all seasons. Chance out there that the water temperature goes ~10C below the air during day time. On the other way around it won't be more than a couple of C if ever happens.

To JimB: The pump is operated using electric motor. What I meant is the problem described by Jaguarjoe.

Most good quality float switches allow for hysteresis to avoid the constant on/off problem. Good float switches are enclosed in a baffle to compensate for any sloshing around. All things considered I would just install a good float switch.

Ron