4.3. Field transistor and relay

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Do curso por Moscow Institute of Physics and Technology

Building Arduino robots and devices

142 classificações

Moscow Institute of Physics and Technology

Building Arduino robots and devices

142 classificações

For many years now, people have been improving their tools, studying the forces of nature and bringing them under control, using the energy of the nature to operate their machines. Last century is noted for the creation of machines which can operate other machines. Nowadays the creation of devices that interact with the physical world is available to anyone. Our course consists of a series of practical problems on making things that work independently: they make their own decisions, act, move, communicate with each other and people around, and control other devices. We will demonstrate how to assemble such devices and programme them using the Arduino platform as a basis. After this course, you will be able to create devices that read the data about the external world with a variety of sensors, receive and forward this data to a PC, the Internet and mobile devices, and control indexing and the movement. The creation of such devices will involve design, the study of their components, the assemblage of circuit boards, coding and diagnostics. Along with the creation of the devices themselves, you will perform visualization on a PC, create a web page that will demonstrate one of your devices, and figure out how an FDM 3D-printer is configured and how it functions. Besides those keen on robotics or looking to broaden their horizons and develop their skills, the course will also be useful to anyone facing the task of home and industrial automation, as well as to anyone engaged in industrial design, advertising and art. The course does not require any special knowledge from the participants and is open even to students of upper secondary school. Programming skills and the level of English allowing to read technical documentation would be an advantage, but this is not obligatory. The entire course is dedicated to practice, so the best way for you would be to get hold of some electronics, follow the illustrated examples and experiment on your own. The kits can be purchased here: kits.cyberphysica.ru. Taught by: Alexey Perepelkin, head of Robotics department in the Laboratory of innovative educational technologies at MIPT Taught by: Dmitry Savitsky, researcher in the Laboratory of innovative educational technologies at MIPT

Na lição

Week 4

After going through Week 4, you will be able to connect your device to a network, plan its creation beforehand , control heavy loads, and power your device correctly.

4.1. Week overview0:50

4.2. Submersible pump2:02

4.3. Field transistor and relay6:40

4.4. Power supply6:47

4.5. Planning6:07

4.6. Think first7:46

4.7. Soil humidity sensor2:16

4.8. Where do web pages come from4:10

4.9. How to transmit data to a network11:35

4.10. How to receive a command from a network8:14

4.11. Finite-state automaton5:13

4.12. WaterMe program basics and switch7:18

4.13. Errors that we often encounter7:03

4.14. The longest sketch so far12:31

4.15. How WaterMe works5:20

Conheça os instrutores

Алексей Перепелкин
Руководитель направления развития цифрового творчества
Центр инновационных образовательных технологий МФТИ
Дмитрий Савицкий
Научный сотрудник
Лаборатория инновационных образовательных технологий МФТИ

Let’s first get acquainted with MOSFET transistor,

which will be the first agent between Arduino and some powerful load.

It has three headers, which are named accordingly: gate, source and drain.

We can see from the diagram what they are necessary for.

It’s written in English here: this is the gate,

that’s the source, and this is the drain.

Consequently we can check which one is which with the help of this diagram.

When we apply voltage to the gate,

the path for the current opens between the source and the drain.

Thus, our load, i.e. the pump, can be

connected between the transistor and

the ground to the plus pole of the power source.

So when we apply voltage from Arduino to the gate,

the path for the current will be open, and the pump will start working.

However, we are not going to use a transistor alone, but the whole

module into which the transistor is fitted, aka the “Power key” module.

Let’s have a closer look at it.

We have the transistor itself here, an LED, which tells us that

a signal is being transmitted to it, and a terminal block which has the load connected to it.

You see, the plus and the minus are marked here,

which means that the polarity of connection is important.

As usual, we connect it to the Troyka shield with a triple cable.

Why is this LED blinking now?

Because I have already uploaded a test sketch to Iskra,

which will allow us to see how this agent works, as well as one more agent which we will examine later.

In this case, voltage is applied to one pin,

and then it is turned off with a 2-second interval.

There is nothing tricky in that – this is simple digital signal control.

Thus, we can see that the LED on the module turns on an off all the time.

In order to make sure that the current flows through the terminal block,

I am going to set the tester to the continuity check mode and will connect it to the terminal block’s outputs.

[SIGNAL] We can see and hear

that the signal is on when the LED is on,

This is exactly when we apply high voltage to pin 7, to which the module is connected.

As a result, it is clear now how to start the pump working.

Such module can have voltage up to 30 V applied to it.

And if we take a separate transistor,

like the one I’ve just shown you, it can have the voltage up to 100 V.

However, don’t get carried away by thinking that you can have

a 220 V alternating current from an electrical outlet running through it. This is a delusion.

One more advantage of working with the MOSFET transistor is that you

can apply impulse ratio modulation

and regulate the load by changing duty cycle.

For example, if you want to connect an LED strip,

you should take the MOSFET transistor or the “Power key” module, and you will be able to

regulate the brightness of the LED strip in the same way as you did with one single LED.

By the way, if you remember, our bright LEDs,

which we, for instance, used in the projector,

have a small transistor fitted into their bodies, like this one.

This is because these LEDs draw powerful currents, which are more than Arduino can normally allow.

What shall we do if we are still planning to work with devices

which draw their power from the 220 V line supply?

We won’t be covering this aspect in our course, but you might as well

have this zeal sometime in the future.

In that case, a relay will help us.

I am going to take a relay of the Troyka module. It is a dual relay with 3 pins.

I am now going to connect it to our testing unit,

And then we shall see and hear how it works.

What is a relay per se?

It mechanically opens or shuts the pass for the signal.

Furthermore, it has three inputs in its terminal block,

one of which is called “normally closed” and the other one “normally opened”.

Thus, one of them carries the current,

when the signal is transmitted to the relay,

and the other one is off when the signal is not transmitted.

Depending on the situation, you can use this or that input.

Let’s look how the pump is connected via the “Power key” module.

Every device has its own wire coloring, which always means something.

For example, the “ground” is usually black, brown or blue.

In our case, both wires of the pump are brown and blue.

In reality, its minus pole is blue, and its plus pole is brown.

Its plus is connected directly to the plus of the power supply unit.

I have connected them via the breadboard, but you can do it, for instance, by

twisting the wires together.

The minus pole (blue) is connected to the power block of the “Power key” module,

and the wire is inserted in the input marked as “plus”.

This is because this section of the circuit is closer to the plus pole.

This blue wire goes from the part of the terminal block marked with “minus”

to the minus pole of the power supply unit.

We have the same test sketch uploaded in Arduino,

which turns pin 7 on and off for 2 seconds.

Pin 7 has the Power key connected to it, Which, in its turn, is connected to the pump.

We can see the water flow for 2 seconds,

and then stop flowing for 2 seconds.

[NOISE]

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