ST STEVAL-BLUEPLUG1 User manual

Introduction

The STEVAL-BLUEPLUG1 evaluation board for home-automation and IoT (internet of things) applications is designed to help

you develop your own home or building automation subsystems for energy management, in a small form factor solution for easy

integration into home and building electrical systems.

The board is compliant with Bluetooth Low Energy (BLE) specification 4.2 to allow secure communication of metering data from

specific electrical loads to a smart phone with BLE support.

You can use an Android application for your smart phone to display energy measurement parameters and send dimming and

scheduling commands to the Smart Plug board.

This board embeds an STPM32 metering chip for high accuracy measurement of power and energy in power line systems using

shunt current sensors, and a non-isolated buck converter supply based on the VIPER06Xs. A three-terminal TRIAC controls the

current through AC switching.

You can also interface the board with NFC enabled EEPROM via a dedicated connector.

Figure 1. STEVAL-BLUEPLUG1 evaluation board - top and bottom

How to use the STEVAL-BLUEPLUG1 evaluation board for home automation

smart plugs

UM2395

User manual

UM2395 - Rev 1 - May 2018

For further information contact your local STMicroelectronics sales office.

www.st.com

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1Safety information

FCC notices

Note: ST reference designs and evaluation boards are intended to help and facilitate development of products. Using

a direct copy of any of them does not waive the requirement for testing and certification of products mandated by

governing agencies and authorities.

This device compiles with part 15 of the FCC Rules. Operation is subject to the following two conditions:

1. This device may not cause harmful interference

2. This device must accept any interference received, including interference that may cause undesired

operation.

Electrical safety

Danger:

Due to the high voltage present on the non-isolated components, special care must be taken to

avoid the risk of electric shocks and burns.

There are no protections against accidental human contact with high voltage components.

Never touch live board components when the board is connected or immediately after the board is

disconnected, as the capacitors may still be charged.

Do not connect probes to any high voltage components if the board is not isolated from the mains

supply, as this may cause damage to equipment.

1. The board must be used only by qualified persons.

2. De-energize the board and all its interface outputs and electrical loads before performing any electrical or

diagnostic operations.

3. Only program and debug the board with the isolated JTAG in-circuit debugger/programmer to avoid

damaging the tools.

4. Use a mains insulation transformer when you perform any tests with spectrum analyzers or oscilloscopes.

Note: STMicroelectronics assumes no responsibility for accidents or injury caused by improper use of this

development tool.

Personal safety

1. Wear personal protective equipment such as latex gloves or safety glasses with side shields, or protect the

EVM in an adequate lucent plastic box with interlocks from accidental touch.

UM2395

Safety information

UM2395 - Rev 1 page 2/22

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2Overview

2.1 Features

• Smart Energy Meter design with wireless connectivity

• BLE (Bluetooth Low Energy) v4.2 connectivity for control and metering panel: Smart-phone connectivity for

energy consumption dashboard, control of appliances

• Dimming: Some loads can be controlled. For example, AC Induction fan speed, Heaters, Incandescent

lamps

• Scheduling: Set the time of day for ON or OFF of the load

• NFC interface: To configure the design, store the logs (connector for adapter board)

• Rated voltage: 240 VAC (typ.)

• Rated current: 12 A (typ.)

• Power consumption of plug: 1.6 W (max.)

• Instantaneous and averaged power

• RMS and instantaneous voltage and current

• Radio certifications:

– FCC certified: S9NSPBTLE1S

– IC certified: 8976C-SPBTLE1S

• CE certified

• RoHS and China RoHS compliant

2.2 Typical applications

• Control and monitoring of energy parameters using BLE.

• Smart metering

• Home automation

• Smart lighting

UM2395

Overview

UM2395 - Rev 1 page 3/22

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2.3 Board architecture

Figure 2. STEVAL-BLUEPLUG1 featured components

1. BTA12-800BWRG (12 A TRIAC)

2. STPM32 (IC for metering applications)

3. SPBTLE-1S (Bluetooth Low Energy v4.2 module)

4. VIPER06 (30 KHz offline converter)

5. STTH110RL (High voltage ultrafast rectifier)

6. L4931 (very low drop voltage regulator)

Figure 3. STEVAL-BLUEPLUG1 block diagram

UART

SWD

GPIOs

dd I2C

STPM32

UART

M24LR

I2C

SDA

VIPER06 L4931

SWD

Debugger

OPTO

BTA12

230 VAC

Phase_in Neutral_in Phase_out Neutral_out

IIN

Zero Crossing

Circuit

LEDs Switch

STEVAL-BLUEPLUG1

230 VAC

Inductive or resistive LOAD

3.3V

Vdd

3.3V

Vdd

3.3V

Voltage Divider

Circuit

VIP

VIN

Shunt

VIPerPLUS

SCK

ST25

IIP

Smart Plug APP

STBTLE-1S SCL

ptional

UM2395

Board

architecture

UM2395 - Rev 1 page 4/22

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The mains supply and loads are monitored by the STPM32 standard metering IC, while the SPBTLE-1S Bluetooth

Low Energy module handles data and command interfacing for the Smart Plug Android app developed for the

board, and can store data via the EEPROM connector.

The 12 A TRIAC acts as a switch for the load and phase controller for dimming.

The supplies for the ICs are regulated from the VIPER06 buck converter output.

The board includes a manual switch to turn the load on and off, and LEDs to signal connectivity status.

2.4 Zero crossing detector circuit

A zero crossing circuit is an electrical circuit that begins operation with the AC load voltage at close to 0 V in the

AC cycle. Zero crossing detection is used for the dimming reference point to fire the TRIAC accordingly.

The circuit has three resistors connected to phase of the AC line to lower the resultant voltage and a resistor on

the base of a PNP transistor which acts as a pull up resistor: when the voltage at the base drops below the base

operating voltage, the transistor switches to output LOW.

Figure 4. Zero crossing detector circuit

R54

270K

DIO6_ZCR

10K

3V3

R53

GND

PHASE

270K

2N3906

R37

R51

10k

270K

R52

The purpose of the circuit in our design is to start the TRIAC conducting very near the moment when the load

voltage crosses zero volts (at the beginning or the middle of each AC cycle represented by a sine wave), so that

the output voltage can be modified by changing the firing angle of TRIAC, which in turn will change the required

output waveform.

UM2395

Zero crossing detector circuit

UM2395 - Rev 1 page 5/22

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Figure 5. Zero crossing detection with oscilloscope

Note: 1. AC voltage

2. Output of the transistor

3. Output of the transistor goes low as ac voltage approaches zero

Figure 6. AC at 50% phase

Note: 1. AC voltage

2. TRIAC Output at 50% duty cycle

2.5 Power supply

For power supply, a non-isolated Buck converter using the VIPER06Xs offline converter is used, with PWM

operation at 30 kHz and frequency jittering for lower EMI. Standby power is very low, at < 30 mW.

This type of supply is ideal for the Smart Plug application, where large currents are not required, but a small form

factor is necessary.

UM2395

Power supply

UM2395 - Rev 1 page 6/22

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Figure 7. Non-isolated buck converter

RR3322

RR3344

PP__IINN

NEUTRAL

VDD

DD11

GND 7

JJ11

RR1111

11..55uuFF 2255VV

SSMMAA

DD22

2277nnFF,,2255vv

CC4444

LIM

CCOONN22

CC4466

CC1177

116600kk

11..55uuFF,,440000VV

LL111100EE,,11WW

GND

RR1100

MMOOVV

CC1188

UU22

11..11mmHH

LL44993311

NN__IINN

SSTTTTHH111100RRLL

PHASE

GND

COMP

GND

110000nnFF,,1166VV

INHIBIT

GND

77..55KK

22..22uuFF,,5500VV

CC4499

8822kk

3V3

333300uuff 1100vv

VVIIPPEERR 0066XXSS

JJ1100

GND

JJ1133

RRVV11

DRAIN 10

DO NOT MOUNT J10, J13

DD44

SSTTTTHH111100RRLL

11..55uuFF,,440000VV

CC4455

CC3366

VOUT

GND

DRAIN

PHASE

NEUTRAL

RR11

UU66

LL66

DRAIN

GND

DRAIN

VIN

CC3344

220000nnFF,,2255VV

REGULATOR

55..11kk

447700uuHH

The output of supply is set to 4.3 V, which is further regulated by the L4931 LDO to 3.3 V and 500 mA, to power

all the analog and digital sections.

UM2395

Power supply

UM2395 - Rev 1 page 7/22

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3Set up the board and connect with the Android app

Warning:

Before performing this task, please review all the safety procedures and precautions associated

with high voltage electrical circuits, and prepare the necessary protection equipment.

Use the procedure below to set up the board.

Step 1. On the evaluation board, connect the input mains and output load connectors.

Input mains connectors:

– P_IN (J10)

– N_IN (J13)

Load connectors:

– P_OUT (J11)

– N_OUT (J12)

Figure 8. Phase (P) and neutral (N) input (IN) and output (OUT) connectors

P_IN P_OUT N_OUT N_IN

J10 J11 J12 J13

Step 2. After powering up the board, RED LED (LD3) will indicate that the board is turned ON.

Step 3. Install the SmartPlug.apk Android app from the release package and launch it.

Figure 9. Smart Plug launch screen

Step 4. Search for the device on your smart phone by selecting the [Plugs found] icon.

Step 5. Connect the device to the App by selecting the Smart_Plug_NRG1 device.

Once connected with the board, the BLUE LED (LD2) will blink at the frequency of 2 Hz.

UM2395

Set up the board and connect

with the Android app

UM2395 - Rev 1 page 8/22

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