S4Aicon.pnglogo_aurd_scra.png

Programming the world:


In this Wiki will guide you to program the word, by reading physical variables (such as temperature, amount of light, rotation position, switch and many others) and by acting to actuator (such as motors, led, light, position servos, buzzer and many others)

The program is coded in S4A (a revision of Scratch able to interact with external elements) and sensors and actuators are in the Arduino shield "scartch-io"


20160126_225704_resized.jpg










Mercury thermometer

Today we are programming a simple but quite didactic exercise. Using the temperature sensor in scratch-io shield (LM35) we can display a mercury thermometer in the screen.
See below the sprites scripts.
A theory pill: LM35 give a voltage proportional to temperature of the package. 0 º centigrade equals to 0mvol, 1º centigrade equals to 10mvol. Knowing that Arduino ADC convert 0to5vol into 1to1024 data... K=2,048 data/º
here you have the script for S4A:



external image LM35-Pinouts.png


thermo.png




Here below, the Arduino script and the mercury 'line' script. See the complete code in the link above for details.
.


therm_2.pngtherm_3.png

































Robotic Arm


You can find detailed guide ans .STL file in these webpages:


external image EBA_thing_06_preview_featured.jpg


Base on this wonderful design of Carlo Franciscone, S4A and Sratch-io shield we create a interesting programming practice where students learn how to build and manage robotic arms.
As any robot we have structure, electronic and progrmaing.

a./ Structure follow this link



b.-/ electronic

We use an Arduino UNO and Scratch-io shield (and the extra pluging we have to add)

As we know S4A version 1.6 only handles three servos but we need four of them to move the arm, so a simple multiplexer plug on shield converts a servo line into two servo lines.

Here you have the schematic of the additional board. we plug this board on top of IO-shield and we connect the four servos of the Arm into the shield as we show in the picture below.


armSCH.png



S4A code has a separate process executed each one second, this procress updates the position of every servo with the value stored in the four variables: waist, shoulder, elbow and hand





structure
#1

Step 1:

Picture of
Picture of



Connect two link arms (003) to the Triangular link (006).
Keep the M4 round heads screws to the inner side like shown on image and selflocking nuts to the outer side.
IMPORTANT
I design all the holes of joints quite exact to allow to make them more precise using a drill bit
The nuts are to be tightened till the locking of the joint, then consequently you must loose them until you obtain a smooth movement with the lower clearance between components. This rule is valid and is to be applied also for the following joint that involve use of self locking nuts.





Step 2:

Picture of
Picture of



Connect link (003) to the rear joint of the horizontal arm (005).
The lower part of the link (003) is to be connected with the vertical drive arm (002) as shown.
Between the two links interpose three M4 washer, this to better align them with the vertical arm
Keep the M4 round heads screws to the inner side and self locking nuts outside


Step 3:

Picture of
Picture of



Connect now the two preassembled links to the forward drive arm (004).
Punt in position horizontal arm (005) and triangular link (006) aligned with the upper connection of the forward drive arm (004). Insert the Ø4 mm brass pipe crossing all the parts and fix it with the M3x30 screw, locked by the nut on the other side.
Verify the freedom of movement and If everything is ok, proceed to the next step.


Step 4: Base assembly

Picture of Base assembly
Picture of Base assembly



Part list:
· n° 1 EBA_01.00.001_base.stl
· n° 1 EBA_01.00.011_round plate.stl
· n° 1 EBA_01.00.010_basement.stl
· n° 1 TowerPro metal gear MG90S servo with double arm horn
· n° 1 servo horn fixing screw
· n° 2 M3 x 15 screw (VTCEI)
· n° 3 M3 nuts


Step 5:


Picture of
Picture of


Immagine 4 3.png
Immagine 4 3.png



Be sure that the servo is in the neutral position than install the double arm horn on the splined shaft keeping the arms parallel to the servo body
Insert the horn inside the housing below the round plate and fix the servo to the plate using one of the two long screw supplied with the servo (the small one in too short due to the thickness of round plate)


Step 6:


Picture of
Picture of


Immagine 8.png
Immagine 8.png



Put in position the base between the two shoulder on the plate and attach together using the two M3 screws and nuts. There two hexagonal housing below, so nuts will be kept in position during tightening

Step 7:


Picture of
Picture of


Immagine 9.png
Immagine 9.png

Immagine 11.png
Immagine 11.png



Align the servo and introduce the wiring in the central part of the basement. Gently pull the wire to make it straight while continue to push in it housing the servo
The wire is then kept in position making it pass through a frontal hole


Step 8: Gripper assembly

Picture of Gripper assembly
Picture of Gripper assembly



Part list:
· n° 1 TowerPro metal gear MG90S servo with single arm horn
· n° 1 servo horn fixing screw
· n° 1 EBA_01.00.012_claw support.stl
· n° 1 EBA_01.00.015_drive gear.stl
· n° 1 EBA_01.00.014_left finger.stl
· n° 1 EBA_01.00.016_driven gear.stl
· n° 1 EBA_01.00.013_right finger.stl
· n° 2 M3 x 20 screw (TCEI)
· n° 3 M3 selflocking nuts


Step 9:

Picture of
Picture of



Attach the servo to the claw support using the two fixing screws supplied

with the servo
Keep the output shaft forward


Step 10:


Picture of
Picture of


Immagine 9.png
Immagine 9.png

Immagine 10.png
Immagine 10.png


Insert the horn in the driven gear then attach the horn at the servo shaft using the supplied screw

The horn has to be aligned forward with the servo in neutral position. Cut the exceeding part of the horn from gear using a cutter



Step 11:

Picture of
Picture of



Insert an M3 screw in the central hole connect it to the claw support then tight the self locking nut checking the freedom of movement

Step 12:


Picture of
Picture of


Immagine 12.png
Immagine 12.png

Immagine 5.png
Immagine 5.png

Immagine 4.png
Immagine 4.png



Insert the two pin of the driven gear into the dedicated holes on the left finger The driven gear has also a shoulder that has to be aligned with the lateral side of the finger. If you find difficulties coupling them, reduce interference using a file.
Once coupled insert an M3 screw in the central hole and attach the finger to the claw support
Now the gripper is ready to be installed on the horizontal arm of the EEzybot
Verify freedom of movement of the gripper manually or using a servo tester


Step 13: Final assembly

Picture of Final assembly
Picture of Final assembly



Now we have the three main sub assembly ready to be connected each other.
Next step we will join the base with the main arms


Step 14:


Picture of
Picture of


Immagine 7.png
Immagine 7.png



To join the base with the main arms align the axis of the parts and insert from one side the brass pipe 24mm long.
Also the short arm of the servo that drive the vertical movement has to be supported by the brass pipe as shown on the pictures.
Check the freedom of movement


Step 15:


Picture of
Picture of


Immagine 11.png
Immagine 11.png



Is time now to install the servo that drive the vertical movement of the arm. Put in the dedicate receptacles two M3x10 hex screw. The servo has to be in the neutral position with the horn at 90 degrees on the right side with the press plate (009) installed (Make the wiring pass through the dedicated enlargment).
Introduce the servo angled in the square seat on the base plate and slide the horn in the shaped housing of the arm that drives the vertical movement. Fixt the press plate against the servo using two M3 nuts


Step 16: Fwd/bckw drive servo


Picture of Fwd/bckw drive servo
Picture of Fwd/bckw drive servo


Immagine 13.png
Immagine 13.png



Sequence for the forward&backward driving servo is similar to the previous. In this case the servo horn has to be installed with the servo in neutral condition aligned vertically.

Step 17: Last link

Picture of Last link
Picture of Last link



attach the latest link to the fixed arm on the rear side of the base using a M4x20 a washer and a selflocking nut

Step 18: Attaching the gripper

Picture of Attaching the gripper
Picture of Attaching the gripper



The last assembly step is to join the gripper to the horizontal arm as shown on the picture.