# Novice, beginner project help

#### levydee

Joined Oct 18, 2016
14
Good afternoon all,

I have started looking into electrical engineering and plan on going to school for it. In the mean time, I have started self studying and want to build a simple circuit, but am not quite sure on the wiring logic involved.

In short,
I want to use a dc water pump to fill water into a container IF the container is below a certain level. I want to use 2 wires connected at the desired level to refill. Once the two wires circuit is completed(by the water filling up), turn the water pump off.

This is a purely educational experiment with as basic components as possible.

Any ideas?

Thanks

#### MrChips

Joined Oct 2, 2009
22,555
Lift the lid on the toilet tank and observe how the cut-off float works.

#### levydee

Joined Oct 18, 2016
14
I was looking for an electrical solution instead of mechanical. I was thinking along the lines of logic gates, but I am not really sure of the circuitry involved.

I have familiarized myself with the essentials(resistors, transistors, 555, decade counter, cap, diodes ect...) and practiced simple circuits using a breadboard. I am just not sure how to use my basic understanding into what I described in the original post.

I have a strong background in programming, but unfortunately that is not translating to well into the physical medium!

#### MrChips

Joined Oct 2, 2009
22,555
So you turn a mechanical action into an electrical one.
The float arm activates a NC-micro-switch. NC stands for Normally Closed.
When the tank is full, the micro-switch contacts open and shut off electrical power to the pump.

#### AlbertHall

Joined Jun 4, 2014
10,787
the common people don't have electrical toilets
I do. The cistern is refilled by a pump with rainwater from the roof.
For the purposes of this thread, there is a magnet fixed to the original float and a reed switch to detect "Full".

#### #12

Joined Nov 30, 2010
18,216
I have a strong background in programming, but unfortunately that is not translating to well into the physical medium!
I guess I'm going to repeat a previous post I made.
Any computer that can not sense or act on the outside world is merely bits in a box. You can build a million of them and they would all sit there terra-flopping without any detectable effect, except maybe the heat they generate.
There is a whole field of science about how to detect and measure the outside world. Sometimes it's analog, sometimes you can get a simple on-off to describe what you're sensing. There is a similar amount of things a computer can command upon an outside device, from turning on a light or starting a motor to showing you that screen you're looking at. Being a great programmer isn't worth a dime if you can't sense or output to the physical world.

Things To Do Today: Learn about IO devices.

#### ci139

Joined Jul 11, 2016
1,696
it's about alternate water level detection methods rather that you should attempt an MCU based project
http://circuitdigest.com/microcontroller-projects/water-level-indicator-project-using-arduino
i was personally thinking of speed of sound differences in air and in water - so another unreliable input detection would be
a transmitter sitting on the bottom of the tank and detector off the water
the primary idea getting a constant water level by 341m/s 1481 m/s

may turn out to be failure in practical coz too little of sound waves´ energy can penetrate the surface
however the discreet water level can be sensed by increased sound signal when mic submerges the benefit is you can have this active sensor set made waterproof
while using the electrodes can have drawbacks

Last edited:

#### levydee

Joined Oct 18, 2016
14
I guess I'm going to repeat a previous post I made.
Any computer that can not sense or act on the outside world is merely bits in a box. You can build a million of them and they would all sit there terra-flopping without any detectable effect, except maybe the heat they generate.
There is a whole field of science about how to detect and measure the outside world. Sometimes it's analog, sometimes you can get a simple on-off to describe what you're sensing. There is a similar amount of things a computer can command upon an outside device, from turning on a light or starting a motor to showing you that screen you're looking at. Being a great programmer isn't worth a dime if you can't sense or output to the physical world.

Things To Do Today: Learn about IO devices.
Ok, I understand that I am new to the forums and am more of a guest than a member at this point in time, but your condescending run-on about my assumed level of ability in software is insulting. Your comment provides absolutely nothing to this thread other than to boast some sort of insinuated superiority upon yourself.

Maybe my original post was deceiving. I am not a tween high school punk who is eager to go to college after I graduate and need a lesson in life. I am already formally educated, worked in my field for some time, and have about 8 years under my belt with software. I just want to switch career directions. I am simply an electronics beginner looking for a little helping hand on a supposedly simple circuit. Toilet banter and silly references are fine, in-fact constructive, this is not.

Please help me, what is I/O again? I swear I have heard of it before.
Communicating with devices and building devices in the physical medium are two vastly different things.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,391
Your giving the guy too much of a hard time.

There is a problem with your logic:

The lack of Hysteresis.

The water level should drop below L1 before the pump turns on, Then the pump should start below L1 and then stop at L2. L1< L2.
"Other" things to be aware of is "Too full" and "empty".

The next question is what kind of sensor will you use?

#### levydee

Joined Oct 18, 2016
14
Your giving the guy too much of a hard time.

There is a problem with your logic:

The lack of Hysteresis.

The water level should drop below L1 before the pump turns on, Then the pump should start below L1 and then stop at L2. L1< L2.
"Other" things to be aware of is "Too full" and "empty".

The next question is what kind of sensor will you use?
I was looking for a simple solution. I looked at and recreated a simple water level detector using only two wires. The water level rises and completes the circuit once the two wire tips are below the level of water(as you described). Can I use this completion of circuit as a switch to turn off the flow of current to the pump?

A simple 555 monostable setup to accommodate a specific fill rate should fix any issues of trigger resolution.

#### #12

Joined Nov 30, 2010
18,216
Novice, beginner
I have started looking into electrical engineering and plan on going to school
I am not a tween high school punk
I am already formally educated,
and you can't figure out how attach one switch to a microprocessor?
Make up your mind.

#### AlbertHall

Joined Jun 4, 2014
10,787
Given that:
This is a purely educational experiment with as basic components as possible.
then yes, Your proposed solution will do the job.
I was looking for a simple solution. I looked at and recreated a simple water level detector using only two wires. The water level rises and completes the circuit once the two wire tips are below the level of water(as you described). Can I use this completion of circuit as a switch to turn off the flow of current to the pump?

#### levydee

Joined Oct 18, 2016
14
Novice, beginner

and you can't figure out how attach one switch to a microprocessor?
Make up your mind.
I am not using a microprocessor. Please read the thread before posting.

#### hp1729

Joined Nov 23, 2015
2,304
it's about alternate water level detection methods rather that you should attempt an MCU based project
http://circuitdigest.com/microcontroller-projects/water-level-indicator-project-using-arduino
i was personally thinking of speed of sound differences in air and in water - so another unreliable input detection would be
a transmitter sitting on the bottom of the tank and detector off the water
the primary idea getting a constant water level by 341m/s 1481 m/s
View attachment 113898
may turn out to be failure in practical coz too little of sound waves´ energy can penetrate the surface
however the discreet water level can be sensed by increased sound signal when mic submerges the benefit is you can have this active sensor set made waterproof
while using the electrodes can have drawbacks
Or a transmitter and detector floating on the top of the water reflecting off the bottom of the tank.

#### AnalogKid

Joined Aug 1, 2013
8,824
At the risk of answering the original question, there are two basic approaches.

1. One sensor. It detects when the water level drops below "full", and turns on the pump until the sensor says the water level is back up to full. One possible drawback is that this makes for many, short pump cycles. One way to extend this so that the pump runs less often is to add hysteresis, either mechanically to the sensor or electrically to the sensor signal (depending on the type of sensor).

2. Two sensors. One is at the "empty" or "low" level, and starts the pump before the tank runs dry. The other is at the "full" level and stops the pump before the tank overfills. This is slightly more complex, but has the advantage of running the pump less often and for longer time periods; both are better for the pump's life than a bunch of short cycles.

Mechanical, optical, thermal, electrical, magnetic, ultrasonic, blah blah blah... Without getting into sensor types or logic diagrams, which approach do you want to investigate first?

ak

Joined Jul 18, 2013
22,048
It sounds as though there is some over-engineering attempted, which is OK if the desire is to obtain experience in different methods and possibilities, but the basic premise outlined in the OP is done in many thousands of installations of Deep well pumps and flood water sump pumps every day by way of a simple float switch.
Max.

#### hp1729

Joined Nov 23, 2015
2,304
It sounds as though there is some over-engineering attempted, which is OK if the desire is to obtain experience in different methods and possibilities, but the basic premise outlined in the OP is done in many thousands of installations of Deep well pumps and flood water sump pumps every day by way of a simple float switch.
Max.
Over engineering? Oh, absolutely. Yes the original post has many simple solutions and many more engineered ones. Don't we love creativity. floats with a switch an be picked up for a couple of dollars. The switch triggers a timer that runs just long enough to fill up the tank. But what fun is that?

Joined Jul 18, 2013
22,048
Yes the original post has many simple solutions and many more engineered ones. Don't we love creativity.
We could always look up a Heath Robinson approach.

@levydee This is a purely educational experiment with as basic components as possible.
You really need to be more specific, and state just what area of control you are interested in first.
There is hard wire logic, IC logic, μp control, only the first qualifies as basic!
Max.

#### BR-549

Joined Sep 22, 2013
4,938
A pressure sensor can give you setpoints for any levels you want. A proportional output allows many control options.

You will have to take some time and study analog devices and their terms and functions.....as related to a high level language.

#### Phil-S

Joined Dec 4, 2015
178
Many ways to solve this.
Real life situations like pumps on water treatment works, where tanks need to be filled or emptied according to required high and low levels, will use a simple robust single float switch which contains a tilt switch. The float is tethered and hysteresis is introduced by altering the length of the tethering cable. This is the basis of many "sump pumps". This is probably not what you want.
Going up a notch in sophistication, look up "hold-on" relays. These give you hysteresis. Use a double-pole changeover relay and two smallish float switches.
CMOS logic devices can do the same job and a simple latch and reset arrangement will do the same job as the relay - these have the advantage that the level sensing can be almost anything - two wires with the conductor exposed at the tip take the place of the float switches - in real life these will be stainless steel probes of different length. Any bipolar transistor (2N3904 e.g.) will sense water (uses the conductivity of water)
Non-contact sensing can use ultrasonics, pressure switches (as mentioned before, universal in washing machines), Honeywell used to do optical devices that detected the difference between the refractive index of water and air.If you want this to work in dirty water like sewage, you use as simple a method as possible and I always opted for ultrasonics.
Ultimately, I would now go down the microcontroller route even though you don't want to.
Total control over all the parameters, many examples using the Arduino. Almost any sensing method can be used.
A bare board ATTiny chip (45/85/841 etc.) is a cheap, reliable method and your application is ideally suited.