#411 Ten Fluid Level (Water Level) Sensors and how to use them (Arduino, ESP32, ESP8266)

Summary

This video explores various sensors for measuring liquid levels, from simple threshold sensors to advanced ultrasonic and pressure sensors. It discusses mechanical and electronic sensors, their mounting inside or outside tanks, and considerations for corrosion resistance and contamination. The video also covers different interfaces like open collector and current loop, and provides insights on connecting these sensors to microcontrollers. It's a comprehensive guide for those looking to monitor liquid levels in different applications.

Takeaways

• 🔍 The video discusses various methods and sensors for measuring liquid levels in different settings, such as home appliances, rural water tanks, and industrial chemical storage.
• 🏡 Two main motivations for the video are presented: monitoring liquid levels remotely in a cottage and avoiding coffee machine water shortages at home.
• 🔄 The video introduces 10 different types of sensors, including threshold sensors, distance sensors, and pressure sensors, each with their unique applications and mounting requirements.
• 🛠 Mechanical threshold sensors are explained, which work by making contact with the liquid and can be made of metal or plastic, raising concerns about corrosion and contamination.
• 📶 Electronic threshold sensors using capacitive or resistive methods are discussed, with an emphasis on their compatibility with plastic tanks and their open collector (OC) output.
• 💧 The importance of considering corrosion resistance and non-contamination when selecting sensors that come into direct contact with liquids is highlighted.
• 📊 For more precise liquid level measurement, the video covers distance sensors that use ultrasonic waves or laser light, and the challenges they face such as corrosion and signal reflection.
• 🔧 Pressure sensors are introduced as an indirect method to measure liquid levels by calculating the pressure at the bottom of a tank, with considerations for sensor placement and compatibility.
• ⚙️ The video also touches on the technical aspects of interfacing sensors with microcontrollers, including the use of resistors, voltage dividers, and analog-to-digital conversion.
• 🔗 The video concludes with a call to action for viewers to share their experiences with different sensors, emphasizing the value of collective knowledge in solving practical problems.

Q & A

What types of liquid level measurement sensors are discussed in the video?

The video discusses sensors that react to fluid level thresholds, sensors that measure the exact fluid level, sensors mounted inside and outside of tanks, and sensors for the top and bottom of tanks.

What are threshold sensors, and how do they function?

Threshold sensors detect when a particular fluid level is reached. They come in two types: mechanical switches or electronic sensors, which can use capacitive or resistive methods. They need to be in contact with the liquid to function.

What are the potential issues with mechanical sensors in liquid environments?

Mechanical sensors can corrode when in contact with liquids, and their material may contaminate the liquid, particularly if they rust.

How do open collector (OC) outputs work and why are they beneficial?

Open collector outputs allow the sensor's output voltage to be independent of the sensor’s supply voltage. By adding a resistor, the output can be controlled and customized, providing flexibility when dealing with varying voltage levels.

What are the differences between time-of-flight sensors using ultrasound and laser light?

Ultrasound sensors use slower sound waves, while laser light sensors (often called LIDAR) use faster light waves. Both measure the distance between the sensor and the liquid surface, but are affected by factors like evaporation, pollution, and tank geometry.

How can pressure sensors be used to measure fluid levels?

Pressure sensors measure the pressure at the bottom of the tank, which correlates to the liquid level based on the specific weight of the fluid. They need access to the tank's lowest point or can be placed directly in the fluid with a long cable.

What are the benefits of using current loop interfaces for long-cable sensors?

Current loop interfaces are robust and efficient for sensors with long cables. They only require two wires to both power the sensor and transmit data, making them straightforward and reliable.

What measures can be taken to prevent sensor corrosion and contamination?

Sensors that come into contact with liquids should be corrosion-resistant and not contaminate the tank’s contents. For internal sensors, materials must be selected carefully, especially in sensitive environments.

What is the advantage of reducing the number of sensor readings in systems where fluid levels don't change rapidly?

By reducing the number of sensor readings, energy consumption is minimized, which is particularly important for electronic sensors that consume power while measuring. This can extend sensor and system longevity.

What mounting considerations should be taken into account for different sensor types?

Different sensors require specific mounting locations. For example, time-of-flight sensors should be mounted on top of the tank to point towards the liquid surface, while pressure sensors must be mounted at the bottom or submerged.

Outlines

00:00

☕ Monitoring Liquid Levels with Sensors

The speaker introduces the concept of measuring liquid levels in various contexts, from coffee machines to water tanks and chemical industries. The video aims to demonstrate 10 different sensors used for this purpose, along with tips and insights into sensor technologies. Two key motivations for the video are mentioned: a request from a colleague to monitor liquid levels remotely in a cottage using LoRa technology, and a personal coffee machine issue. The speaker also hints at addressing various types of sensors, mounting methods, and how to connect them to microcontrollers.

05:00

📏 How Threshold Sensors Work

This section explains how threshold sensors work, focusing on mechanical and electronic versions. The speaker highlights three mechanical sensors (two made of metal and one plastic) and emphasizes their need to be in contact with the liquid, which can lead to corrosion or contamination. The description also touches on how to read these sensors using a microcontroller and resistor. Electronic sensors, such as capacitive ones, can be mounted outside plastic tanks. Open collector outputs are introduced, offering flexibility in managing output levels without depending on the sensor’s VCC voltage.

10:02

🔋 Flexibility of Open Collector Outputs

The speaker elaborates on the flexibility of open collector outputs, which allow for different output levels based on the voltage applied to the resistor. This section shows how to get either 3.3V or 5V output depending on how the resistor is connected, making it possible to power devices such as LEDs or relays. Additionally, the speaker explains the advantages of using these sensors to detect low or high liquid levels in tanks. Resistive moisture sensors are introduced as another option for measuring levels, but with warnings about corrosion and contamination.

📡 Measuring Liquid Levels with Sensors

This section dives into sensors that measure exact liquid levels, discussing two main methods: using distance sensors or pressure sensors. The speaker details the time-of-flight principle, either with ultrasound or laser light (LIDAR), and the potential challenges like corrosion, tank geometry, or pollution affecting readings. They also touch on different types of sensors, including waterproof ultrasonic ones, and the importance of testing sensors in specific environments. The focus shifts to pressure sensors, emphasizing their use for measuring liquid levels indirectly based on fluid pressure at the tank's bottom.

🌊 Using Pressure Sensors for Accurate Liquid Monitoring

Here, the speaker continues explaining the use of pressure sensors to measure liquid levels by placing them inside or outside the tank. Pressure sensors must be selected based on their suitability for liquids (not airspeed), and accuracy can be measured using internal or external ADCs. The section also explains how current loop interfaces are advantageous for long cables and robust data transmission. The speaker gives a formula for calculating the appropriate resistor to convert current to voltage and highlights the need for protection against corrosion for both the sensor and the cable.

🧪 Conclusions and Learnings on Liquid Level Sensors

The final section summarizes the key takeaways from the video, highlighting the differences between digital and analog output sensors. Digital sensors react when a specific fluid level is reached, while analog sensors provide a proportional signal. The speaker stresses the importance of mounting sensors correctly—inside, outside, at the top, or bottom—and ensuring they are resistant to corrosion and contamination. Various sensor interfaces, including current loop and open collector outputs, are explained. The speaker closes by inviting viewers to share their experiences with different sensors to build collective knowledge.

Keywords

💡Liquid Level Sensors

Liquid level sensors are devices used to monitor the level of liquids in various containers, such as coffee machines, water tanks, or industrial chemical storage. In the video, these sensors are crucial for automating the monitoring process and preventing issues like running out of water or overfilling. The script discusses different types of sensors, including threshold sensors, which detect when the liquid level reaches a certain point, and distance sensors, which measure the exact level of the liquid.

💡Threshold Sensors

Threshold sensors are a type of liquid level sensor that trigger an action or send a signal when the liquid level reaches a certain pre-set level. They are essential for preventing overflows or detecting when a container is empty. The video mentions two varieties of threshold sensors: those with mechanical switches and those with electronic sensors, which can use capacitive or resistive methods to detect the liquid level.

💡Mechanical Switches

Mechanical switches are a component of some threshold sensors that physically move or change state when the liquid level reaches a certain point. They are typically made of metal or plastic and must be in contact with the liquid to function. The video discusses how these switches can be connected to a microcontroller through a resistor to read the voltage level, indicating the liquid's presence or absence.

💡Capacitive Method

The capacitive method is an electronic approach used in some liquid level sensors to detect the presence of a liquid by measuring changes in capacitance when the liquid comes into contact with the sensor. This method is non-contact and can be used with plastic tanks. The video explains how this type of sensor can be used for a coffee machine project and how it works with an open collector output.

💡Open Collector Output

An open collector output is a type of electronic output used in some sensors, including the capacitive liquid level sensor discussed in the video. It allows for a flexible connection to a microcontroller, as the output voltage level can be set independently of the sensor's power supply voltage. This is useful for interfacing with different voltage levels in a system, as the output can be adapted to match the microcontroller's input requirements.

💡Moisture Sensors

Moisture sensors are a type of sensor that can detect the presence of moisture or liquid. In the context of the video, they are suggested for use in threshold measurement and, for small tanks, even for measuring the level of the liquid. These sensors need to be placed inside the tank and require a conducting fluid to operate. The video cautions about the potential for corrosion and contamination with these sensors.

💡Time of Flight Sensors

Time of flight sensors measure the distance to an object by emitting a signal and measuring the time it takes for the signal to return after bouncing off the object. In the video, these sensors are used to measure the liquid level by mounting them on top of the tank and pointing them towards the liquid surface. The script mentions both ultrasonic and laser (LIDAR) types, which have different ranges and applications.

💡Pressure Sensors

Pressure sensors are used to measure the pressure exerted by a fluid at a certain point, such as the bottom of a tank. In the video, pressure sensors are discussed as an indirect method for determining liquid level, as the pressure at the bottom of a tank is related to the height of the liquid column above it. The script explains how these sensors can be used with a current loop interface for long cable runs and how they output a voltage proportional to the pressure.

💡Current Loop Interface

A current loop interface is a type of electrical interface used for transmitting analog signals over long distances with high reliability. In the video, it is mentioned as a method used by some pressure sensors to send data. The sensor outputs a current between 4 and 20 milliamperes, which can be converted to a voltage by connecting a resistor in series. This method is robust against electrical noise and is suitable for sensors with long cables, as it only requires two wires for both power and signal transmission.

💡Microcontroller

A microcontroller is a small computer on a single integrated circuit that can be programmed to perform specific tasks, such as reading sensor inputs and controlling outputs. In the video, microcontrollers are central to connecting and utilizing the various liquid level sensors discussed. The script explains how different sensors can be interfaced with a microcontroller, whether through digital or analog inputs, and how to handle different output types like open collector or current loop.

Highlights

Measuring liquid levels is a common problem across various settings, from coffee machines to industrial chemical tanks.

The video showcases 10 different sensors for liquid level measurement, each with unique applications and methods.

Threshold sensors are available in mechanical or electronic forms, with the latter using capacitive or resistive methods.

Mechanical sensors must be in contact with the liquid, raising concerns about corrosion and contamination.

Electronic sensors offer the advantage of not needing contact with the liquid, reducing the risk of contamination.

The video demonstrates how to read mechanical sensors using a 10k ohms resistor and an input pin on a microcontroller.

Open collector output sensors are highlighted for their flexibility in output voltage levels, independent of the sensor's VCC.

The video explains the use of moisture sensors for threshold measurement, especially suitable for small tanks.

Electronic sensors consume energy during measurement, but power consumption can be managed with smart switching.

For precise liquid level measurement, distance sensors using ultrasound or laser light are discussed.

The video addresses the challenges of ultrasonic sensors, including corrosion and signal reflection issues.

Pressure sensors are introduced as an indirect method to measure liquid levels by calculating fluid pressure at the tank's bottom.

The video provides practical advice on mounting sensors, considering factors like tank geometry and liquid surface conditions.

Current loop interface is recommended for sensors with long cables due to its robustness and simplicity.

The video concludes with a call to action for viewers to share their experiences with different sensors, fostering a community of knowledge exchange.

The video provides a comprehensive overview of fluid level sensors, their interfaces, and practical considerations for various applications.

Transcripts

measuring levels of liquids is a common

problem

where i live it's probably more the

water level of the coffee machine

in rural areas the level of a water tank

and in the industry the level of

chemical substances

there are many different ways to get

this job done

if you stick around i will show you 10

different sensors and as usual we will

learn some new tricks crazy youtubers

here is the guy with the swiss accent

with a new episode and fresh ideas

around sensors and microcontrollers

remember if you subscribe you will

always sit in the first row

two things motivated me to begin this

video

the first was a colleague who manages a

remote cottage

he asked me if it would be possible to

use laura to monitor two critical levels

of liquids from remote instead of always

driving to the cottage

the second motivation was completely

different

during my home office days i drink a lot

of coffee my wife works out of home and

does not often use our coffee machine

but she hates it if the machine is out

of water when she wants to brew her only

cup of coffee in the morning because i

did not fill it up the day before

of course this is the mistake of the

coffee machine

it only shows the empty tank if you

start the next one

inferior engineering which brings me

into deep trouble as you can imagine

so i need a proactive water level sensor

anyway in this video we will cover much

more

sensors that react on fluid level

thresholds

sensors that measure the fluid level

sensors that have to be mounted inside

and sensors that are mounted outside the

tanks

sensors for the top

and for the bottom of the tanks

and as usual you get some background

info on the sensors

interfaces i will not test the accuracy

of the sensors in this video but i will

show you how you can connect them to a

typical microprocessor

let's start with the threshold sensors

they come in two varieties with a

mechanical switch or with electronics

the electronic sponge uses either the

capacitive or the resistive method

these are three typical examples of

mechanical sensors two of them are made

of metal

and the third of plastic

all have to be in contact with the

liquid to work

which can create a few problems

first does the liquid corrode the

sensors and second

can the material of the sensors

contaminate the liquid

particularly if they start to rust if

any of the above questions have to be

answered with yes we have to use

different sensors

but first how can we read these sensors

very simple if we connect them through a

10k ohms resistor to vcc we can read the

voltage level with an input pin

be aware that they bounce so you have to

take measures against it in software

the easiest is just to wait a few

milliseconds before the next reading

while open they do not need energy and

even could be used to switch your mcu on

and off

this sensor uses electronics and the

capacitive approach

it has to be mounted outside the tank

but it only works with plastic tanks

this sensor will be used for my coffee

machine project by the way

it is rated from 5 to 24 volts and has a

so-called open collector or oc output

because this is a commonly used concept

we have a look at it

most mcus or sensors provide two output

levels for low and high in our case 0

and 3.3 or 5 volts

this is simple and for many applications

the right approach

this sensor is different

do you know why they choose this

interface

let's assume we power the sensor with 5

or even 12 volts

then the output voltage for high also

could be 5 or 12 volts and we would have

to deal with it at a later stage

usually we would use a voltage divider

to reduce the voltage to the appropriate

level

the open collector output offers a

different solution

what happens if we add a resistor and

connect it to 3.3 volt then the output

voltage will be 0 when the transistor

conducts and 3.3 volts when open

if we connected the resistor to 5 volts

we would get 0 or 5 volts you see the

output level is independent from vcc of

the sensor

and if the transistor is strong enough

we can replace the resistor with an led

or a relay

a typical pin of an esp32 only can

source or sync 12 milliampere

open collector outputs usually are rated

higher

this sensor supports 50 milliampere for

example

here are examples of mounting these

sensors to detect low or high fluid

levels and they even suggest a solution

for metal tanks

we could also use the moisture sensors

discussed in video number 207

for threshold measurement

and for small tanks even to measure the

level

they have to be placed inside the tank

and these resistive sensors need a

conducting fluid

everything said about corrosion and

contamination applies here too

just remember these sensors corrode very

fast

electronic sensors other than their

mechanical counterparts use energy while

measuring if the levels do not move fast

you can reduce the number of readings

and switch your sensors vcc with a pin

of your mcu and only switch it on for

the measurements

if your sensor does not consume more

than 12 milliampere you can connect it

directly to an esp output pin

if it needs a higher current you have to

add a p channel fit to switch it

but what if you need more than a low or

a high level

then we basically have two possibilities

we measure the exact liquid level using

distance sensors or measure the pressure

at the bottom of the tank

the pressure method is called an

indirect method because it does not

measure the fluid level

but you can calculate it if you know the

specific weight of the fluid

we know two ways of measuring distance

both use time of flight

one uses the slower waves of ultrasound

and the other the fast waves of laser

light

the laser type sometimes is called lidar

for both methods the sensors must be

mounted on top of the tank and point

into the direction of the liquid surface

one thing of caution standard ultrasonic

sensors will corrode if water evaporates

for example and both sensors suffer from

pollution created if condensed vapors

clock them

i assume that a time of flight sensor or

a waterproof ultrasonic sensors like

this one should survive a few years but

you have to try in your particular

situation

another problem with ultrasonic sensors

is when signals are reflected by places

other than the surface of the liquid

these effects are influenced by the tank

geometry and the surface of the inner

tank

this may be the reason for the unique

design of this sensor

how do we connect these time-of-flight

sensors to our mcus

for most of them you find a library and

example projects on the internet

so i will not cover it here

you find the led lidar in video number

119 and the ultrasonic sensors in videos

number 40 and 190.

the range of the lidars is either 2 or 4

meters the ultrasonic sensors promise a

range up to 7 meters but i would not

trust these values and try the sensors

in your environment particularly the

laser sensors can be influenced by

sunlight

consider also the minimum measuring

distance and mount your sensors at least

at this distance from the maximum liquid

level

if the tank is closed at the top maybe

you cannot mount one of those sensors

fortunately there is another possibility

we measure the pressure at the bottom of

the tank

we get lots of pressure sensors make

sure you get one for liquids and not for

airspeed like this one

and because the sensor usually is in

contact with the liquid the same rules

apply as for the internal level sensors

this is an example of such a sensor it

can measure up to 30 psi

which means around 20 meters of water

this sensor runs on 5 volts and outputs

a voltage between 0.5 and 4.5 volts

so we can read it either with an

internal adc or if we do not trust its

accuracy with an external adc as shown

in video number 340.

obviously with pressure sensors we need

access to the tank's lowest point

if there is no such possibility we have

another possibility we can use a

pressure sensor inside the liquid at the

bottom of the tank

therefore it needs a long cable of

course the sensor and the cable have to

be protected against corrosion and

contamination

this sensor by the way uses a so called

current loop interface which is a

brilliant idea for sensors with long

cables it only needs two wires to power

the sensor and transmit the data

this sensor can be powered by 12 to 24

volts and returns its values as a

current between 4 and 20 milliampere if

we connect a resistor in series to the

sensor we get a voltage that is

proportional to the pressure

and if we connect the resistor to the

ground we can easily measure this

voltage with an adc the resistor can be

calculated with ohm's law if we want 3.3

volts at 20 milliampere we get a value

of 165 ohms

if we want to calibrate it to a lower

pressure it becomes higher of course

these are all possibilities i wanted to

cover

maybe you add other ones i forgot or i

do not know

and it would be fantastic if you shared

your experience with the different

sensors i'm sure that together we will

have a lot of knowledge

what are the learnings

we get fluid level sensors with digital

as well as analog output signals

digital if they react when a particular

level is reached and analog if they

output a signal proportional to the

fluid level

sensors can be mounted inside or outside

of the tank

if they contact the fluid they have to

be corrosion resistant and must not

contaminate the tank's content

each sensor type has one mounting

location time of flight sensors have to

be mounted on top and pressure sensors

at the bottom for example

different sensors use different

interfaces the current loop is robust

and straightforward for long cables and

analog readings open collector is a very

flexible way to connect different things

to the output pin as well as create

different output voltages

that was all for today as always you

find the relevant links in the

description

i hope this video was useful or at least

interesting for you if true please

consider supporting the channel to

secure its future existence thank you

bye