In general, while designing electronics projects the loads are controlled (switched ON or OFF) using microcontroller block. But, for this purpose the circuit requires relays, acting as controlled switches (for different circuits different types of relays are used). Depending on the signals received from the microcontroller or other control circuits the relay controls the load. The relay consists of continuous power supply and whenever it gets driven or gets control signal then the relay gets activated and loads can be turned ON or OFF. But, primarily we must know what is a relay driver circuit.

• Uln2803 Stepper Motor Driver Circuit Board
• Uln2803 Stepper Motor Driver Circuit
• Uln2803 Stepper Motor Driver Circuit Breaker
• Uln2803 Stepper Motor Driver Circuit Diagram

Relay Driver Circuit

To drive a stepper motor successfully (as for example, the unipolar 28BVJ-48 with its driver board ) what is needed is:-1. A circuit to make about 500mA flow through 4 coils. And in the right order. And with the right timing. This is can be done with logic circuits (or a program) and separate buffers, and four pins. ULN2803 is a high-voltage and high-current Darlington transistor array and is mainly used as a relay driver with an ability to handle 8 relays at a time.It comes with a collector-emitter voltage around 50 V and input voltage residing at 30 V. Before we move further, we must know what is Darlington transistor? 4, 5, 6, and 8-wire Stepper Motors: 'Help'. This is a common word during discussions involving peculiarities of step motors, which can have 4, 5, 6, and 8 wires. But today, I can say that this type of engine is no longer such a difficult challenge, as they are starting to get more.

The circuit used for driving a relay can be termed as a relay driver circuit and it can be designed using various integrated circuits. These relays are needed to be driven for activating or to turn ON. So, relays require some driver circuitry to turn ON or OFF (based on the requirement).The relay driver circuit can be realized using different integrated circuits such as ULN2003, CS1107, MAX4896, FAN3240, A2550, and so on. Here, in this article let us discuss about relay driver circuit using ULN2003. Before discussing in detail about a relay driver circuit, let us know about IC ULN2003.

Relay Driver IC ULN2003

The IC ULN2003A is a Darlington transistor array which deals with high-voltage and high-current. There are various types of relay driver ICs such as a high side toggle switch, low side toggle switch, bipolar NPN transistor, Darlington transistor, N-channel MOSFET, ULN2003 driver IC.

The pin diagram of IC ULN2003A is shown in the above figure which consists of 16 pins. The IC ULN2003A comprises of 7-NPN Darlington pairs as shown in the internal schematic diagram and is typically used to switch inductive loads (dissipates voltage spikes if any using suppression diode) and to drive stepper motors.

Relay Driver Circuit using ULN2003

It is difficult to use a number of relays with transistors, so, relay driver IC ULN2003A can be used for availing more relays. We can use seven relays with relay driver circuit using ULN2003 and the relay driver circuit using ULN2803 enables to use eight relays. The above circuit represents the interfacing of PIC microcontroller (PIC16F877A) with relays using a relay driver circuit with ULN2003. The clamp diodes are built in these relays driver ICs and which eliminates the usage of freewheeling diodes.

The program that can be used for turning the relays ON and OFF is given below with delay time of one second.

void main()
{
TRISD = 0x00; //PORT D is made as output
do
{
PORTD.R1 = 1; //Relay 1 turns ON
PORTD.R2 = 1; //Relay 2 turns ON
PORTD.R3 = 1; //Relay 3 turns ON
PORTD.R4 = 1; //Relay 4 turns ON
PORTD.R5 = 1; //Relay 5 turns ON
PORTD.R6 = 1; //Relay 6 turns ON
PORTD.R7 = 1; //Relay 7 turns ON…and so on.
Delay_ms(1000); // 1 second Delay
PORTD.R1 = 0; //Relay 1 turns OFF
PORTD.R2 = 0; //Relay 2 turns OFF
PORTD.R3 = 0; //Relay 3 turns OFF
PORTD.R4 = 0; //Relay 4 turns OFF
PORTD.R5 = 0; //Relay 5 turns OFF
PORTD.R6 = 0; //Relay 6 turns OFF
PORTD.R7 = 0; //Relay 7 turns OFF
Delay_ms(1000); //1 second Delay
}
while(1);
}

Based on the signals received from the microcontroller the relay driver circuit drives the relay or relays ON and OFF, such that controlling the operation of loads connected to these relays.

Practical Implementation of Relay Driver Circuit

Uln2803 Stepper Motor Driver Circuit Board

This is an innovative electrical engineering project that eliminates the power supply interruptions by auto power supply from (integrating and controlling) the four different electric power sources such as solar power, mains power supply, generator, and inverter. This project utilizes microcontroller of 8051 family which is interfaced with four switches (these switches or selection keys are assumed to be four different power sources mentioned above). Thus, the absence or failure of specific power source can be represented by pressing a particular switch or key.

The project consists of different block such as microcontroller block, power supply block, relay driver, relays, LCD display, and load (here a lamp is used for demonstration purpose) as shown in the block diagram. The input signals to the microcontroller are given using these press switches. Thus, the microcontroller generates the appropriate output signal and is fed to the relay driver circuit using ULN2003. Hence, the relay driver circuit drives the appropriate relay based on the control signals received from the microcontroller. So, the load gets turned ON by utilizing the available power source. The source that is used for turning ON loads can be displayed on the LCD display.

Do you know other practical applications of relay driver circuit using ULN2003? Then, share your views, comments, ideas, and suggestions by posting in the comments section below.

This page features a Unipolar Stepper Motor driver that uses an EDE1200, Unipolar, Stepper Motor Controller IC produced by eLab Digital Engineering.

Five stepper motor control functions are provided: Step, Half-stepping, Direction, Free running and Outputs disabled.

The circuit uses a ULN2803 darlington driver as its output device that can drive motors drawing up to 1.0 amperes per phase.

A printed circuitboard and parts are available for this circuit.

email

If you are interested in printed circuit boards please send an email to the following address: rpaisley4@cogeco.ca Subject: EDE1200 Unipolar Stepper Driver - ULN2803

EDE1200 - Unipolar Stepper Driver PCB Schematic

Devices Used For This Circuit

• EDE1200 Unipolar Stepper Motor Controller IC. Provides all control inputs and generates the output's drive patterns.

• ECS Inc. ZTT-4.00MG - 4.0MHz Ceramic Resonator ( Digikey Part X902-ND ) Generates the CLOCK frequecy used by the EDE1200 chip.

• ULN2803 - 8 Segment, Darlington, High Current, High Voltage Peripheral Driver. In this circuit 2 output segments are connected in parallel allowing a maximum output current of 1 amp per phase.

• LM7805 - Positive 5 Volt Regulator. Provides regulated power for the EDE1200 IC and can supply power to external control circuits.

  For a 12 volt supply, external circuits can draw up to 100 milliamps.

  For a 24 volt supply, external circuits can draw up to 25 milliamps.

It is not the purpose of this page to provide full explanations of how these devices work. Detailed explanations can be found through datatsheets that are available from many source on the internet and from suppliers.

EDE1200 - Unipolar Stepper Driver Controller Inputs

This EDE1200 Stepper Motor Controller circuit has the following control inputs and modes of operation:

1. DISABLE MOTOR DRIVERS - When the DISABLE MOTOR DRIVERS input (Pin 6) is LOW, the four coil driver outputs of the EDE1200 are switched OFF and the the motor can be turned freely, regardless of the other input states.

2. STEP INPUT - Each time the STEP input (Pin 9) goes LOW, the motor will move one step, depending on how the other four inputs are set.

3. HALF STEP MODE - When the HALF STEP input (Pin 10) is LOW, the motor will move in Half Steps.

4. DIRECTION - The DIRECTION input (Pin 7) controls the motor's direction of rotation depending on the input level (HIGH or LOW). The motor's true direction of rotation depends on order that the motor's coils are connected to the driver.

5. FREE RUN MODE - When the FREE RUN input (Pin 10) is HIGH, the motor will run at the pulse rate at the STEP INPUT (Pin 9). When the RUN input (Pin 10) is LOW, the motor will run at 1 of 8 preset speeds that are set by 3 DIP switches (S1A, S1B and S1C) mounted on the the circuitboard.

All of the control inputs to the EDE1200 are pulled up to 5 volts through 3.3K ohm resistors.

For more detailed explanations of controls for the EDE1200, refer to the devices datasheet which can be found on this eLab Digital Engineering page.

• The circuit requires an external oscillator or other source to provide the STEP input signal. This input must be between '0' and +5 volts and be free of noise and bounce to prevent false stepping. A 555 timer circuit or logic device would be suitable as an input. Open collector devices will also work as each of the inputs has a 'pull-up' resistor. A 4.7uF capacitor and a push button switch connected to the STEP input will also work.

• All other inputs can be switches or electronic inputs but should not be allowed to bounce while the motor is running.

FREE RUN Mode - Speed Table

Uln2803 Stepper Motor Driver Circuit

NOTE: The speeds indicated in the FREE RUN mode tables are approximate and will vary with the resonator's (X-1) actual oscillating frequency.

NOTE: The following tables have been copied directly from the eLab Digital Engineering datasheet for the EDE1200 IC.

EDE1200 Stepper Controller Test Circuit

The following circuit was used to test the operation and functions of the EDE1200 stepper driver circuit. In actual circuits, the inputs should be noise and bounce free although a toggle switch will work.

Stepper Circuit Board Parts

Two sources for the EDE1200 Stepper Motor Controller IC are:

1. eLab Digital Engineering - The manufactures 'Product Overview' page - Part EDE1200

2. Jameco Electronics Part Number - 141532

All other components or their equivalents are available from a number suppliers. (DigKey part numbers are shown.)