Filter By

Availability

Availability

Selections

Selections

Price

Price

  • BDT 0.00 - BDT 230,000.00

Categories

Categories

Brand

Brand

Condition

Condition

Weight

Weight

  • 0 kg - 2,500 kg

Resistor Pack of 5

Resistor Pack of 5

  • Banner

Active filters
  • Availability: In stock
  • Categories: Back in Stock
  • Categories: Display
  • Categories: HMI
  • Categories: Motor
  • Categories: PLC
  • Condition: New

Reference: RBD-2161

6 DOF Aluminium Mechanical Robotic Arm Manipulator Kit

(0)
Build a versatile robotic arm with six degrees of freedom. Control the arm with a microcontroller or compatible control system. Customize the arm with different end-effectors or tools. Learn about robotics and automation concepts while building your own robot arm. Perform small-scale industrial automation tasks with ease. Pick and place objects with...
BDT 4,250.00
BDT 4,250.00 tax incl.
BDT 4,250.00 tax excl.
BDT 4,250.00 tax excl.
BDT 4,250.00 tax incl.
BDT 4,250.00 tax incl.
BDT 0.00 Tax
BDT 4,250.00 tax excl.
BDT 4,250.00 tax excl.
BDT 0.00 Tax
BDT 4,250.00 tax incl.
More
In-Stock
In stock: 13

Reference: RBD-1217

Nextion NX3224T024 - Generic 2.4" TFT LCD Touch Display

(0)
Nextion is a seamless Human Machine Interface (HMI) solution. Nextion provides a control and visualization interface between a human and a process, machine, application or appliance.  Nextion is mainly applied to Internet of thing (IoT) or consumer electronics field.
BDT 3,099.00
BDT 3,099.00 tax incl.
BDT 3,099.00 tax excl.
BDT 3,099.00 tax excl.
BDT 3,099.00 tax incl.
BDT 3,099.00 tax incl.
BDT 0.00 Tax
BDT 3,099.00 tax excl.
BDT 3,099.00 tax excl.
BDT 0.00 Tax
BDT 3,099.00 tax incl.
More
In-Stock
In stock: 15

Reference: RBD-0949

Submersible 3V Mini DC Water Pump with Wire Horizontal Type

(0)
Operating Voltage : 2.5 ~ 4V Operating Current : 130 ~ 220mA Flow Rate : 80 ~ 120 L/H Maximum Lift : 40 ~ 110 mm Outlet Outside Diameter: 7.5 mm Outlet Inside Diameter: 5 mm
BDT 160.00
BDT 160.00 tax incl.
BDT 160.00 tax excl.
BDT 160.00 tax excl.
BDT 160.00 tax incl.
BDT 160.00 tax incl.
BDT 0.00 Tax
BDT 160.00 tax excl.
BDT 160.00 tax excl.
BDT 0.00 Tax
BDT 160.00 tax incl.
More
In-Stock
In stock: 33

Reference: RBD-0467

S7-300 SM322 6ES7 321-1BH01-0AA0

(0)
Model: S7-300 SM322 Part No: 6ES7 321-1BH01-0AA0 Made in Germany SIMATIC S7-300, DIGITAL INPUT SM 321, OPTICALLY ISOLATED, 16DI, 24VDC, 20 PIN
BDT 25,000.00
BDT 25,000.00 tax incl.
BDT 25,000.00 tax excl.
BDT 25,000.00 tax excl.
BDT 25,000.00 tax incl.
BDT 25,000.00 tax incl.
BDT 0.00 Tax
BDT 25,000.00 tax excl.
BDT 25,000.00 tax excl.
BDT 0.00 Tax
BDT 25,000.00 tax incl.
More
In stock
In stock: 6

Reference: RBD-2264

65mm Rubber Wheel

(0)
Tire with sponge liner for more strength With upgraded tire tread for greater friction New design wheel for better combination with the motor Diameter: 65 mm Width : 28 mm The material of Wheel: High-strength plastic The material of Tire: Rubber Color: Blue Rim Black Tire. Motor Shaft coupling not included buy it here.
BDT 320.00
BDT 320.00 tax incl.
BDT 320.00 tax excl.
BDT 320.00 tax excl.
BDT 320.00 tax incl.
BDT 320.00 tax incl.
BDT 0.00 Tax
BDT 320.00 tax excl.
BDT 320.00 tax excl.
BDT 0.00 Tax
BDT 320.00 tax incl.
More
In-Stock
In stock: 38

Reference: RBD-1218

Nextion NX8048T050 - 5.0" LCD TFT HMI Touch Display

(0)
Model No.:NX8048T050 Display Type:011R(R:Resitive Touchscreen) Operating Voltage (VDC):4.75 ~ 7 Max. Operating Current (mA):410 Touch Type: Resistive Colors:65K (65536)
BDT 10,590.00
BDT 10,590.00 tax incl.
BDT 10,590.00 tax excl.
BDT 10,590.00 tax excl.
BDT 10,590.00 tax incl.
BDT 10,590.00 tax incl.
BDT 0.00 Tax
BDT 10,590.00 tax excl.
BDT 10,590.00 tax excl.
BDT 0.00 Tax
BDT 10,590.00 tax incl.
More
In-Stock
In stock: 6

Reference: RBD-0950

RS-360 Mini DC 4-12V Water Pump Motor

(0)
Model : RS-360 micro-motors small pump Operating voltage : 4V-12V Current : 0.8A Motor diameter : 27 mm Pump Length : 52 mm Out of the water hole diameter : 4 mm Weight : 70g
BDT 450.00
BDT 450.00 tax incl.
BDT 450.00 tax excl.
BDT 450.00 tax excl.
BDT 450.00 tax incl.
BDT 450.00 tax incl.
BDT 0.00 Tax
BDT 450.00 tax excl.
BDT 450.00 tax excl.
BDT 0.00 Tax
BDT 450.00 tax incl.
More
In-Stock
In stock: 23

Reference: RBD-0468

S7-300 SM331 6ES7 331-7KF02-0AB0

(0)
Model: S7-300 SM331 Part No: 6ES7 331-7KF02-0AB0 Made in Germany SIMATIC S7-300, ANALOG INPUT SM 331, FLOATING, 8AI, RESOLUTION 9/12/14 BITS, U/I/THERMOCOUPLE/RESISTANCE ALERT, DIAGNOSTICS; 1X20PIN REMOVE/INSERT W. BACKPLANE BUS
BDT 55,000.00
BDT 55,000.00 tax incl.
BDT 55,000.00 tax excl.
BDT 55,000.00 tax excl.
BDT 55,000.00 tax incl.
BDT 55,000.00 tax incl.
BDT 0.00 Tax
BDT 55,000.00 tax excl.
BDT 55,000.00 tax excl.
BDT 0.00 Tax
BDT 55,000.00 tax incl.
More
In stock
In stock: 5

Reference: RBD-1967

Brand: Hakko Corporation

Hakko Original FX888D-06BY Digital Soldering Station

(0)
Hakko Original FX888D-06BY Digital Soldering Station 220V~70W 50/60 Hz Hakko Corporation Japan (Original) Made in Malaysia Mfg: 2022.02
BDT 16,590.00
BDT 16,590.00 tax incl.
BDT 16,590.00 tax excl.
BDT 16,590.00 tax excl.
BDT 16,590.00 tax incl.
BDT 16,590.00 tax incl.
BDT 0.00 Tax
BDT 16,590.00 tax excl.
BDT 16,590.00 tax excl.
BDT 0.00 Tax
BDT 16,590.00 tax incl.
More
Last items in stock
In stock: 2

Reference: RBD-1219

3.5inch LCD Display Shield for Arduino

(0)
Supports development boards such as Arduino UNO and Mega2560 for plug-in use without wiring 480X320 resolution, clear display Support 16-bit RGB 65K color display, display rich colors 8-bit parallel bus, faster than serial SPI refresh On-board 5V/3.3V level shifting IC, compatible with 5V/3.3V operating voltage Easy to expand the experiment with SD card...
BDT 1,680.00
BDT 1,680.00 tax incl.
BDT 1,680.00 tax excl.
BDT 1,680.00 tax excl.
BDT 1,680.00 tax incl.
BDT 1,680.00 tax incl.
BDT 0.00 Tax
BDT 1,680.00 tax excl.
BDT 1,680.00 tax excl.
BDT 0.00 Tax
BDT 1,680.00 tax incl.
More
In-Stock
In stock: 8

Reference: RBD-0951

N20 DC 6V 200RPM Mini Metal Gear Motor

(0)
This is a DC Mini Metal Gear Motor, ideal for making robots Lightweight, high torque and low RPM. Fine craftsmanship, durable, not easy to wear. With excellent stall characteristics, can climb hills easily. You can also easily mount a wheel on the motor’s output shaft.
BDT 350.00
BDT 350.00 tax incl.
BDT 350.00 tax excl.
BDT 350.00 tax excl.
BDT 350.00 tax incl.
BDT 350.00 tax incl.
BDT 0.00 Tax
BDT 350.00 tax excl.
BDT 350.00 tax excl.
BDT 0.00 Tax
BDT 350.00 tax incl.
More
In-Stock
In stock: 200

Reference: RBD-0469

S7-300 SM322 6ES7 322-1BL00-0AA0

(0)
Model: S7-300, SM322 Part No: 6ES7 322-1BL00-0AA0 Made in Germany SIMATIC S7-300, DIGITAL OUTPUT SM 322, OPTICALLY ISOLATED, 32DO, 24V DC, 0.5A, 1 X 40 PIN, SUM OF OUTPUT CURRENTS 4A/GROUP (16A/MODULE)   6ES7 322-1BL00-0AA0  
BDT 25,000.00
BDT 25,000.00 tax incl.
BDT 25,000.00 tax excl.
BDT 25,000.00 tax excl.
BDT 25,000.00 tax incl.
BDT 25,000.00 tax incl.
BDT 0.00 Tax
BDT 25,000.00 tax excl.
BDT 25,000.00 tax excl.
BDT 0.00 Tax
BDT 25,000.00 tax incl.
More
Last items in stock
In stock: 2

Reference: RBD-2027

2 Pin Pitch 5.0mm Straight Pin Screw PCB Terminal Block Connector Blue

(0)
5.08mm pitch. Pin header: Tin plated brass. Contacts: Nickel plated brass. Strong, compact, lightweight. Heat resistant.
BDT 8.00
BDT 8.00 tax incl.
BDT 8.00 tax excl.
BDT 8.00 tax excl.
BDT 8.00 tax incl.
BDT 8.00 tax incl.
BDT 0.00 Tax
BDT 8.00 tax excl.
BDT 8.00 tax excl.
BDT 0.00 Tax
BDT 8.00 tax incl.
More
In-Stock
In stock: 644

Reference: RBD-1251

7 Inch TFT IPS Monitor for Raspberry Pi

(0)
Input Voltage: DC 7.4~35V. Input Current: DC 0.5A-1.5A. Power Consumption: ≤8W Watts. Resolution: 1024 x 600. Aspect Ratio: 16:9 & 4:3. Contrast Ratio: 500:1. Monitor Mount is not Available.
BDT 6,390.00
BDT 6,390.00 tax incl.
BDT 6,390.00 tax excl.
BDT 6,390.00 tax excl.
BDT 6,390.00 tax incl.
BDT 6,390.00 tax incl.
BDT 0.00 Tax
BDT 6,390.00 tax excl.
BDT 6,390.00 tax excl.
BDT 0.00 Tax
BDT 6,390.00 tax incl.
More
In-Stock
In stock: 10

Reference: RBD-0470

S7-300 SM331 6ES7 331-7PF01-0AB0

(0)
Model No: S7-300, SM331 Part No: 6ES7 331-7PF01-0AB0 Made in Germany SIMATIC S7-300, ANALOG INPUT SM 331, OPT. ISOL.,2/3/4 WIRE, 8AI, RESISTANCE, PT100/200/1000 NI100/120/200/500/1000, CU10, PLUS CHARACTERISTICS ACCORDING TO GOST STANDARD 16 (INTERN 24) BIT, 50MS, 1 X 40 PIN
BDT 76,000.00
BDT 76,000.00 tax incl.
BDT 76,000.00 tax excl.
BDT 76,000.00 tax excl.
BDT 76,000.00 tax incl.
BDT 76,000.00 tax incl.
BDT 0.00 Tax
BDT 76,000.00 tax excl.
BDT 76,000.00 tax excl.
BDT 0.00 Tax
BDT 76,000.00 tax incl.
More
In stock
In stock: 5

Reference: RBD-2021

4 Pin JST-XH Male Straight Connector 2.54mm Pitch

(0)
Current Rating: 3A Voltage Rating: 250V Connector Type: Header JST-XH 4 Pin Connector
BDT 9.00
BDT 9.00 tax incl.
BDT 9.00 tax excl.
BDT 9.00 tax excl.
BDT 9.00 tax incl.
BDT 9.00 tax incl.
BDT 0.00 Tax
BDT 9.00 tax excl.
BDT 9.00 tax excl.
BDT 0.00 Tax
BDT 9.00 tax incl.
More
In-Stock
In stock: 486

Reference: RBD-1108

0.56 Inch 3 Digit 7 Segment Red Common Cathode Display

(0)
Bright Red LED chip, which is made from AlGaAs on GaAs substrate Blackface and RED LED segments Type: Common cathode No. of Pins: 12 Low Current Consumption High Brightness
BDT 50.00
BDT 50.00 tax incl.
BDT 50.00 tax excl.
BDT 50.00 tax excl.
BDT 50.00 tax incl.
BDT 50.00 tax incl.
BDT 0.00 Tax
BDT 50.00 tax excl.
BDT 50.00 tax excl.
BDT 0.00 Tax
BDT 50.00 tax incl.
More
In-Stock
In stock: 93

Reference: RBD-1061

6V TT DC Gear BO Motor Dual Shaft

(0)
Low density: lightweight, low inertia. Capability to absorb shock and vibration as a result of elastic compliance. Ability to operate with minimum or no lubrication, due to inherent lubricity. The relatively low coefficient of friction. Operating Voltage(VDC): 3~12 Shaft Length (mm): 8.5 Shaft Diameter (mm): 5.5 (Double D-type) No Load Current: 40-180mA....
BDT 85.00
BDT 85.00 tax incl.
BDT 85.00 tax excl.
BDT 85.00 tax excl.
BDT 85.00 tax incl.
BDT 85.00 tax incl.
BDT 0.00 Tax
BDT 85.00 tax excl.
BDT 85.00 tax excl.
BDT 0.00 Tax
BDT 85.00 tax incl.
More
In-Stock
In stock: 185

Reference: RBD-0471

S7-300 SM331 6ES7 331-1KF01-0AB0

(0)
Model: S7-300, SM331 Part No: 6ES7 331-1KF01-0AB0 Made in Germany SIMATIC S7-300, ANALOG INPUT SM 331, OPTICALLY ISOLATED, 8 AI, 13 BIT RESOLUTION, U/I/RESISTANCE/PT100, NI100, NI1000, LG-NI1000, 66 MS MODULE UPDATE, 1 X 40 PIN 6ES7 331-1KF01-0AB0  
BDT 45,000.00
BDT 45,000.00 tax incl.
BDT 45,000.00 tax excl.
BDT 45,000.00 tax excl.
BDT 45,000.00 tax incl.
BDT 45,000.00 tax incl.
BDT 0.00 Tax
BDT 45,000.00 tax excl.
BDT 45,000.00 tax excl.
BDT 0.00 Tax
BDT 45,000.00 tax incl.
More
In-Stock
In stock: 4

Reference: RBD-1068

N20 12V 100 RPM Micro Metal DC Gear Motor

(0)
This is a DC Mini Metal Gear Motor, ideal for making robots Lightweight, high torque and low RPM. Fine craftsmanship, durable, not easy to wear. With excellent stall characteristics, can climb hills easily. You can also easily mount a wheel on the motor’s output shaft.
BDT 295.00
BDT 295.00 tax incl.
BDT 295.00 tax excl.
BDT 295.00 tax excl.
BDT 295.00 tax incl.
BDT 295.00 tax incl.
BDT 0.00 Tax
BDT 295.00 tax excl.
BDT 295.00 tax excl.
BDT 0.00 Tax
BDT 295.00 tax incl.
More
In-Stock
In stock: 13

Reference: RBD-0914

MAX7219 4 Channel Dot Matrix Display Panel

(0)
Driver Chip: MAX7219 Input Voltage: 3.7 to 5.3 V Input Current: 320 mA Display Dimensions: 32x32x6 (LxWxH) mm PCB Dimensions: 128×32 (LxW) mm
BDT 650.00
BDT 650.00 tax incl.
BDT 650.00 tax excl.
BDT 650.00 tax excl.
BDT 650.00 tax incl.
BDT 650.00 tax incl.
BDT 0.00 Tax
BDT 650.00 tax excl.
BDT 650.00 tax excl.
BDT 0.00 Tax
BDT 650.00 tax incl.
More
In-Stock
In stock: 27

Reference: RBD-0472

S7-300 SM 323 6ES7 323-1BL00-0AA0

(0)
Model: S7-300,SM 323 Part No: 6ES7 323-1BL00-0AA0  Made in Germany SIMATIC S7-300, DIGITAL MODULE SM 323, OPTICALLY ISOLATED, 8 DI AND 8 DO, 24V DC, 0.5A AGGREGATE CURRENT 2A, 1X20 PIN
BDT 35,000.00
BDT 35,000.00 tax incl.
BDT 35,000.00 tax excl.
BDT 35,000.00 tax excl.
BDT 35,000.00 tax incl.
BDT 35,000.00 tax incl.
BDT 0.00 Tax
BDT 35,000.00 tax excl.
BDT 35,000.00 tax excl.
BDT 0.00 Tax
BDT 35,000.00 tax incl.
More
Last items in stock
In stock: 3

Reference: RBD-2182

3D Printer Nozzle M7 Thread Brass 1.75mm

(0)
Filament Support: 1.75mm Material: High-quality brass Color: Brass color Screw outer diameter: M7 If you are not sure which Nozzle size to choose, Please check our guide in the documentation tab below. 
BDT 190.00
BDT 190.00 tax incl.
BDT 190.00 tax excl.
BDT 190.00 tax excl.
BDT 190.00 tax incl.
BDT 190.00 tax incl.
BDT 0.00 Tax
BDT 190.00 tax excl.
BDT 190.00 tax excl.
BDT 0.00 Tax
BDT 190.00 tax incl.
More
In-Stock
In stock: 28

Reference: RBD-1305

0.56 Inch 1 Digit 7 Segment Red Common Cathode Display

(0)
Bright Red LED chip, which is made from AlGaAs on GaAs substrate Blackface and RED LED segments Type: Common anode No. of Pins: 10 Low Current Consumption High Brightness
BDT 17.00 BDT 20.00
BDT 20.00 BDT 17.00 tax incl.
BDT 20.00 BDT 17.00 tax excl.
BDT 20.00 BDT 17.00 tax excl.
BDT 20.00 BDT 17.00 tax incl.
BDT 20.00 BDT 17.00 tax incl.
BDT 0.00 BDT 0.00 Tax
BDT 20.00 BDT 17.00 tax excl.
BDT 20.00 BDT 17.00 tax excl.
BDT 0.00 BDT 0.00 Tax
BDT 20.00 BDT 17.00 tax incl.
More
In-Stock
In stock: 99

Reference: RBD-1114

DC3-12V N20 Gear Motor & Mount Bracket & 43mm Wheel

(0)
N20 Micro Gear 12V 100RPM DC Motor (High Torque) Mounting Bracket for N20 Micro Gear motors 3PI miniQ Car wheel Tyre 44mm N20 DC Gear Motor Wheel
BDT 480.00
BDT 480.00 tax incl.
BDT 480.00 tax excl.
BDT 480.00 tax excl.
BDT 480.00 tax incl.
BDT 480.00 tax incl.
BDT 0.00 Tax
BDT 480.00 tax excl.
BDT 480.00 tax excl.
BDT 0.00 Tax
BDT 480.00 tax incl.
More
In-Stock
In stock: 10

Reference: RBD-0473

S7-300 SM323 6ES7 323-1BH01-0AA0

(0)
Model: S7-300,SM323   Part No: 6ES7 323-1BH01-0AA0     Made in Germany     SIMATIC S7-300, DIGITAL MODULE SM 323, OPTICALLY ISOLATED, 16 DI AND 16 DO, 24V DC, 0.5A, AGGREGATE CURRENT 4A, 1X40 PIN
BDT 35,000.00
BDT 35,000.00 tax incl.
BDT 35,000.00 tax excl.
BDT 35,000.00 tax excl.
BDT 35,000.00 tax incl.
BDT 35,000.00 tax incl.
BDT 0.00 Tax
BDT 35,000.00 tax excl.
BDT 35,000.00 tax excl.
BDT 0.00 Tax
BDT 35,000.00 tax incl.
More
Last items in stock
In stock: 2

Reference: RBD-2141

Anti-Corrosion Water Level Sensor with Ball Float Switch

(0)
Rating contract (Max.): 10 W Switching power supply (Max.): 110VDC Resistance contract (Max.): 100 Ω Appro. Float Ball Size (mm) : 24×17 (LxD) Body Total Length (mm) : 85 Cable Length (cm) : 37 Total Float opening: 70° Switch ON/OFF angle Approx. betn 15° to 20°
BDT 350.00
BDT 350.00 tax incl.
BDT 350.00 tax excl.
BDT 350.00 tax excl.
BDT 350.00 tax incl.
BDT 350.00 tax incl.
BDT 0.00 Tax
BDT 350.00 tax excl.
BDT 350.00 tax excl.
BDT 0.00 Tax
BDT 350.00 tax incl.
More
In-Stock
In stock: 39

Reference: RBD-1306

8*8 LED matrix module common anode of LED matrix

(0)
Easy to Install on Breadboard. Bright LED lights. Compact Design. LED Size: 3mm. Configuration: Common Anode.
BDT 95.00
BDT 95.00 tax incl.
BDT 95.00 tax excl.
BDT 95.00 tax excl.
BDT 95.00 tax incl.
BDT 95.00 tax incl.
BDT 0.00 Tax
BDT 95.00 tax excl.
BDT 95.00 tax excl.
BDT 0.00 Tax
BDT 95.00 tax incl.
More
In-Stock
In stock: 78

Reference: RBD-1248

Miniature Vibrating Motor

(0)
Speed(RPM):19000 Motor diameter: 6mm Shaft diameter: 0.8mm Shaft length: 4mm Rated voltage: 1.5V-3.1V
BDT 150.00
BDT 150.00 tax incl.
BDT 150.00 tax excl.
BDT 150.00 tax excl.
BDT 150.00 tax incl.
BDT 150.00 tax incl.
BDT 0.00 Tax
BDT 150.00 tax excl.
BDT 150.00 tax excl.
BDT 0.00 Tax
BDT 150.00 tax incl.
More
In-Stock
In stock: 50

Reference: RBD-0474

S7-300 SM322 6ES7 322-1HH01-0AA0

(0)
Model: S7-300, SM322 Part No: 6ES7 322-1HH01-0AA0 Made in Germany SIMATIC S7-300, DIGITAL OUTPUT SM 322, OPTICALLY ISOLATED 16DO, RELAY CONTACTS, 1 X 20 PIN
BDT 25,000.00
BDT 25,000.00 tax incl.
BDT 25,000.00 tax excl.
BDT 25,000.00 tax excl.
BDT 25,000.00 tax incl.
BDT 25,000.00 tax incl.
BDT 0.00 Tax
BDT 25,000.00 tax excl.
BDT 25,000.00 tax excl.
BDT 0.00 Tax
BDT 25,000.00 tax incl.
More
In-Stock
In stock: 4

Reference: RBD-1249

Shaftless Vibration Motor

(0)
Voltage Range: DC 2.5-4V. Motor Diameter: 10 mm. Motor Thickness: 3.4 mm. Min. Rated Speed: 9000RPM Max. Rated Current: 90mA
BDT 150.00
BDT 150.00 tax incl.
BDT 150.00 tax excl.
BDT 150.00 tax excl.
BDT 150.00 tax incl.
BDT 150.00 tax incl.
BDT 0.00 Tax
BDT 150.00 tax excl.
BDT 150.00 tax excl.
BDT 0.00 Tax
BDT 150.00 tax incl.
More
In-Stock
In stock: 73

Reference: RBD-0688

RF Transmitter Receiver Pair 433 MHz

(0)
Wide input supply (2.5 V to 12V) Easy to integrate (V+, GND, and Data) The device in deep sleep mode when Data pin is grounded Very small dimension.
BDT 117.00
BDT 117.00 tax incl.
BDT 117.00 tax excl.
BDT 117.00 tax excl.
BDT 117.00 tax incl.
BDT 117.00 tax incl.
BDT 0.00 Tax
BDT 117.00 tax excl.
BDT 117.00 tax excl.
BDT 0.00 Tax
BDT 117.00 tax incl.
More
In-Stock
In stock: 145

Follow us on Facebook