Basic Gripper Usage (miniBloq)

Introduction

Sparki has a gripper. It will be useful to learn how to use it before we move to more complex tasks. And of course, we will use the gripper in future lessons.

The gripper is a simple mechanism driven by a stepper motor, the same kind of motor used to move Sparki’s wheels. The stepper motor’s shaft has a pinion attached, which drives a rack:

Thus, moving the motor in one direction opens the gripper, while moving the motor in the other direction closes it.

Programming the Gripper

Having learned this, we are now going to program the gripper’s movements.  Please remember to check that the batteries are properly connected (and charged!). And as we are going to use the motors here, please check that the On/Off Switch is on. Another important thing to take care of when playing with the robot’s motors is to be careful not to be working over a table. A fall from that table could permanently damage your Sparki. The basic blocks that miniBloq provides to control the gripper are the open, close and stop blocks:

As there is no sensor to detect if the gripper is fully closed or fully opened, we will control it moving its motor during small time intervals. And to determine the intervals that we should use to open and close it, we will need to experiment a little before going further. So, before we start, make sure that the gripper is not fully opened nor fully closed:

 Be careful if you find that the gripper is in one of the positions shown in the previous image, since trying to move it during long intervals of time when it’s blocked may damage the motor. For example, if the gripper is closed (as shown in the left photo), you should try first to open it a bit with a simple program like this: On the other hand, if you see that the gripper is fully opened (like the right photo in the previous image), please run a program like the following: Now, try making small modifications to the time interval. For example, you can open (or close) it for 2 seconds. Please don’t try big numbers here, since you will reach the gripper’s mechanical limit fast. By making a few little experiments with the intervals of time, you will soon be familiarized with the gripper’s limits. You can try any combination of these blocks to drive Sparki’s gripper: This small program will cycle your Sparki’s gripper, opening it for 1 second (1000 milliseconds) and closing it for 1 second too:  

SparkiDuino Programming Environment

This lesson is also available for the SparkiDuino Programming Environment. SparkiDuino will allow you to program your Sparki using standard Arduino syntax.