CONTROL OF DC MOTORS FOR MEDICAL CHAIR

In this project we will carry out a DC motor control system for a medical chair in a clockwise and anticlockwise direction with short protection in the turns.

GERBER PCB:

https://mega.nz/file/uQgwWaDB#ZbuY98pIYuKCWIvW09nrNvlXylaZ1joK58CLQluva7k

Here we will see the schematic diagram made in the easyeda software with all the electronic components and their respective values.

the control element is the relay. It is much simpler, supports a much higher current motor, has less voltage drop, and the motor can use another voltage source (ie, it is theoretically isolated). The problem is that relays have a limited useful life, high frequency PWM cannot be used, and the relay coil adds considerable consumption in the case of driving low current motors.

Mainly, there are three types of DC motor control:

Off/On: The motor can be turned off and on

Off/Forward/Reverse: Motor can be turned off and rotated in both directions

Off/Forward/Reverse/Braking: In addition to the above, there is an extra state in which the motor is turned, short-circuiting its pins

In addition, in some cases it is possible to control the speed of the motors, for example through pulse width modulation (PWM), as long as the system allows it (if it is made with slow components such as relays, it cannot be done).

In the case of wanting to use PWM, it will be necessary to generate the signal with a sufficiently high frequency so that the carrier is not heard when the motor is running. Usually, a frequency of more than 19 KHz is enough. It should be noted that a higher frequency almost always implies a greater loss in the elements that interrupt the current of the motor.

If the motor specifications are not very complex, it is possible to find several integrated H-bridges that carry out all the control and the power part in the same package, avoiding the need to design it. For example, a common one is the L293D and L298.

In this project we will carry out the control of a medical chair, it has 3 motors such as kickstand and stretcher that can be raised or lowered by means of buttons that control these motors at 24VDC.

Basically we could define the relay as an electrical switch that allows the passage of electrical current when it is closed and interrupts it when it is open, but that is electrically activated, not manually.

The relay is composed of a coil connected to a current. When the coil is energized, it produces an electromagnetic field that causes the normally open relay contact to close, allowing current to flow through a circuit to, for example, light a lamp or start a motor. When we stop supplying current to the coil, the electromagnetic field disappears and the relay contact opens again, leaving the electrical circuit that went to that lamp or motor without current.

What are the relays for?

The relays are used to activate a circuit that has a considerable consumption of electricity through a small power circuit -12 or 24 volts- that magnetizes the coil. Suppose we want to motorize a garage or farm entrance door. For this we will need a remote control that manages to activate through a receiver that small power charge that starts the operation of the relay: the coil will magnetize and close the electrical circuit that feeds the motor that is used to open the door. We can also use it to turn on machines and motors, lighting systems, etc.

Sometimes, we find ourselves with lighting circuits that need great power for their operation. By activating and deactivating them indirectly, through the use of relays that work with little power, we prevent possible risks and accidents.

In the automotive industry, relays are also widely used to activate fans, windshield wipers, horns, window regulators, etc. The turn signal relay allows the light to flash when activated and to emit the characteristic sound when it is on.

relay types

There are different types of relays:

Electromechanical relays that have variants depending on the activation mechanism. They can be of the armature, mobile core, reed or reed type, polarized relays or tripolar relays.

Solid state relays, which are used in situations where there is continuous use of the relay contacts and a higher switching speed is required.

AC relays.

Delayed action or timer relay. With these relays it is achieved that the connection or disconnection is done after a certain time.

Thermal relays. They are used to protect motors from overloads. They have metal sheets inside that deform more or less depending on the heat. If they reach a certain deformation point because the heat of the motor has increased, they open the circuit and do not let the current pass.

Arduino relay. With an Arduino board we can control a relay. We only have to connect the relay to one of the 5 volt pins that this board has. By programming the board we can obtain interesting results to control lighting and motor ignitions.

• 6 RELAYS 24VDC 5 PINS
• 6 RELAYS 24VDC DOUBLE 8 PINS
• 2 DIODES 1N5819(SL) SMD
• 6 RESISTORS 4.7K 1206 SMD
• 6 DIODES LEDS GREEN 0805 SMD
• 1 RESISTOR 0 ohms 1206 SMD
• 4 BLOCK TERMINALS 2 PINS GREEN
• 1 CAPACITOR 1000UF50V
• 12 DIODES 1N4007 SMD (M7)
• 1 PCB

• VIN 24VDC
• I MAX 10A
• CONTROL OF 3 MOTORS
• HOURLY AND COUNTERCLOCKWISE CONTROL
• PROTECTION SYSTEM AGAINST SUCK TURN INVERSION
• EFFICIENT AND EFFECTIVE PROJECT

This project was made in the Easyeda software as we can see the tracks and the 3D image of the project working perfectly are no difficulty

PCBWAY has 10 years in the electronics industry manufacturing professional PCBs, assembling PCBs managing to satisfy the demands of all parts of the world, in addition to meeting the highest quality and delivery time standards. PCBWAY allows the manufacture of your PCBs from 5 units.

This project was carried out thanks to PCBWAY, a company dedicated to the manufacture of prototypes and professional PCBs, in addition to offering you a ready assembly service with all the components in your PCBS, complying with the established quality and delivery time standards.

We thank PCBWAY, a leading company for manufacturing and assembling professional PCBs with the highest quality, PCBWAY has fair reasonable prices, punctual shipping time and 24-hour customer service, it also offers you the option of quoting all its services in his web page. Do not think twice and start manufacturing your professional PCBs from 5 units safely.

10pcbs at $5 order them here www.pcbway.com

We thank PCBWAY for the professional pcb they provide us for this project.

GERBER PCB:

https://mega.nz/file/uQgwWaDB#ZbuY98pIYuKCWIvW09nrNvlXylaZ1joK58CLQluva7k