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Small autonomous robot driven by two servos of 3.7 grams with continuous rotation.

Powered by a Li-ion battery of 3.7V and 70mA MicroServo Motors 3.7 grams H-Bridge LB1836M soic 14 pin Doc: https://www.onsemi.com/pub/Collateral/LB1836M-D.PDF Microcontroller ATTiny24A soic 14 pin 2KB Flash memory, 128 bytes SRAM memory, 128 bytes EEPROM memory, 12 inputs / outputs & many other functions. Documentation: http://www.microchip.com/wwwproducts/en/ATtiny24A Obstacle detection Infrared sensor Sharp IS471F and Led IR 2mm CQY37N Motion in darkness by photoresist detection (LDR of 5mm) and two white LEDs 3mm Fires backs two red LEDs 3mm. Programmed in BASIC with BASCOM AVR USBasp programmer.

Step 1: Material:

1 x Attiny24A Soic 14 pin

1 x LB1836M Soic 14pin

1 x Li-ion Battery 70mA 3.7V

1 x inter micro cms for PCB

1 x LDR mini

1 x IS471F sharp

1 x CQY37N IR LED 2mm

1 x red LED SMD 1206

2 x white LED 3mm

2 x red LED 3mm

1 x Pin Header Pin

2 x resistors 10 Kohms SMD 1206 (LED signal obstacle and Reset), 2 x resistors 220 ohms SMD 1206 (lighting), 1 x resistor 150 Kohms SMD 1206 (dark detection)

2 x 100nF SMD 0805 (Reset and power supply), 2 x 470nF SMD 0805 (interference suppression of motors)

2 x Servo Motors 3.7 Gram Rotation 360 °

2 x seals plumbing15mm glued on wheels of recovery

1 x Positive Sensitive Double-Sided Positive Epoxy, Positive Developer, Iron Perchloride, UV Insole Cynolite or araldite glue, transparent tape Soft copper, wire the smallest diameter possible strand of strand 0.75 mm², multi strand Rigid copper wire 1.5 mm² (for the rear tail), Soldering iron, 0.5mm solder, tweezers straight beak, cutting pliers, magnifying glasses, acetone Flux for welding SMD

USBasp Programmer, Multimeter (to test the insulation of the tracks and their continuity)

Step 2: Construction:

This inexpensive mini robot that can walk in a room, avoids most obstacles, detects shadows and lights its front lights, also turns its rear lights backwards.

It moves thanks to its two servos of 3.7 grams modified to work in continuous rotation, its brain is an Attiny24A microcontroller; 14-pin and 2KB flash memory Its unique eye is composed of an IR detector from Sharp the IS471F guided by a 2mm IR LED, A 1206 CMS LED that it detected an obstacle. The construction of the PCB requires attention because it is double-sided and the tracks are tight. On the programming side, I used a simple language and performing the basic BASCOM AVR. My programmer is in USB connection it is a USBASP intended for the microcontrollers of the AMTEL family.

The printed circuit:

For the circuit, I used Kicad version 4.02 stable (free and powerful thanks to its author), the installation can be done in several languages and there are tutorials on the internet. It can be downloaded for different operating systems here: Kicad

If you do not want to use Kicad I have attached to the ZIP the two types for printing the PCB in SVG format that can be printed with Internet Explorer (or modify with the free vector drawing software InkScape) You can download InkScape here: https://inkscape.org/

Kicad screenshots will help you place components and weld the 14 straps between the two faces of the IC.

Tip: If the double face causes you problems, a simple trick make two single-sided ICs drill the holes for the components on each IC and stick them back to back after soldering some components for the tracking.

Step 3: Place and Weld Components

ATTENTION the tracks are very ready one of the others:

Before welding the components, check (with the meter and the magnifying glass and transparently by putting a lamp behind) that no tracks touch or are cut and remove the copper circle that was used to cut the IC because it touches Several tracks. Assembly of components: Clean both sides thoroughly with acetone To facilitate welding the ideal is to dip the IC in a cold tinning bath (I did not do it) Drill all pellets with a 0.8mm forest Coat the two flow faces for cms Weld the 14 straps first with a strand of stranded strand (delicate operation) Welding the cms components after having coated them with flux in order resistors, cms LEDs, capacitors, Integrated circuits and welding the other components.

Step 4: Glue the Servos on Support

For engines I have used 3.7 grams modified servomotors for a continuous rotation, it is rather delicate but possible.On both servomotors the gears had no limit stop rotation (this is not the case for all servos of this type), I just had to remove the integrated potentiometer and cut all the electronics.

Once the servos have been modified and reassembled, it is necessary to put tape to keep them waterproof (especially if you stick them with a glue like cyanoacrylate or araldite) then they are glued on the piece of epoxy of the same diameter as the PCB Whose copper is removed by engraving or 1 mm thick plastic. The wheels are screwed onto the servo accessory (supplied with) and cut slightly at the ends.

Step 5: Programming and Assembly

When all components are soldered, clean with acetone and recheck thoroughly before you start programming. The program of the microcontroller was written in BASIC with BASCOM AVR which is powerful and of which one can download a free version here: BASCOM

For the programmer you are spoiled for choice: I used a USBasp that can be purchased on Amazon or Ebay.

In the pictures of BASCOM AVR tow important icons: compilation which allows to compile the BASIC program before loading it in the microcontroller. Programming that allows to load the program into the flash memory or to

configure the Fuses. The Lock and Fuse bits window allows you to configure the parameters of the microcontroller

ATTENTION: The Fuse H must always be at 0 (Enable serial programming) it is it that allows me dialogue between PC and microcontroller (otherwise the chip is blocked and unrecoverable).

There is a reset circuit for this kind of incident, it is to build itself, I built it, it saved me many times thanks to its author :).

Here's the link in English: FuseBitDoctor

Step 6: Final Assembly :)

For the case I used a mini soda bottle that I cut with windows on demand as it was a little too wide, I cut it high and taped for a diameter of 4cm. The finished PCB is then glued to the wheel support using hot-melt gun or 2-component epoxy.

Now Have Fun :)

All files for construction and programming here: all files

I'm French and my English is not very good if you see some bad expression please send me a message and i will rectify.

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