In this blog post we will take a look at the driver board that comes with the Make:it Robotics Starter Kit. There is no documentation that comes with the Start kit concerning the Driver board other than the schematic.
Unless you have some experience reading schematics the task of understanding what is on the driver board and how to use it beyond the kits that Radio Shack provides might be a bit daunting.
So we are going to show some images of the driver board and the schematic and point out some of important parts and map these to the schematic so everyone can follow along and learn more about the driver board. Lets start out easy:(Click on the images for a larger view of the image)
Here is a an image of the motor board with some terminal connectors marked in red and yellow.
The yellow box drawn on the driver board image is the terminal connector for power into the driver board from the battery boxes.
If you remember when you built the robot, you wired the two battery boxes in series (the black lead from one battery box was wired to the red lead of the other battery box.
Then one lead from each box was wired to the terminal connectors on the driver board). If you take a voltage reading on the two connectors of the driver board, you should get a reading of around 12 volts.
Unless you are interested in understanding how the power circuit was built, you really do not need to speed too much time reading the schematic.
The two red boxes drawn on the image of the driver board are the motor terminal connectors. The left terminal connector is for motors 1 and 2. The right terminal connector is for motors 3 and 4.
Above are images of the schematics of the motor driver circuit. Again if you are not interested in learning how the circuit is designed then you should not have to spend much time looking over the schematic.
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Step 1: Make:it Robotics Starter Kit - More Sensors
Let us now look at some more built in sensor inputs that our driver board has. Look at the below driver board image, I have drawn some square boxes on the image:
If you have built the line following robot than you should be familiar with the 4 sets of pins on the right side of the board, marked in red.
These are the connectors for the two line following optical sensors.
The 4 sets of pins on the left side of the board, marked in yellow are for the the IR (infrared) proximity sensors. These sensor pins are not used in the Make:it Robotics Starter Kit. They are used on one or both of the later add on kits that are available from Radio Shack or the Maker Shed store.
At the time of this writing, I have not purchased the add on kits. I will update this section after I purchase the kits. The 4 sets of pins, marked in green are for LED (light emitting diodes), again not used in the Make:it Robot Starter Kit. The three pins, marked in blue are for the remote IR sensor, another add-on kit that you can purchase.
I have not included a schematic for these sets of pins, as the schematics are quite large. But the connectors are labeled quite clearly on the schematic. If you are interested, take a look at the schematic to become familiar with what other components they connect to.
Step 2: Serial Jumpers
One of the most critical jumper pins on the Driver board is marked in red above:
These jumpers when connected, as shown, allow the program running on the Arduino to communicate through the serial port to the driver board.
If the pins are not jumpered as shown in the image, the robot will not move when you turn on the battery boxes.
The purpose of the jumpers, when removed, is to allow you to use the USB port on the Arduino, to upload a new program to the robot. After uploading the program you should re-attach the jumpers as shown so the Arduino can communicate to the driver board.
Step 3: Extra Pins for Custom Sensors
One of the nice features of the Driver board that comes with the Make:it Robotics Starter Kit is that there are extra Arduino pins on the Driver board that are not used.
These extra port pins can then be used to enhance the robot with features of your own design.
For those that are not familiar with the Arduino design.
A board that plugs into the Arduino is called a Shield. The Arduino family of micro-controller boards have rows of female headers around the board. These header pins are used to interface sensors and other external devices that can be used to communicate to the outside world.
An Arduino shield has male header pins on the bottom of the board that fit directly into the female header pins on the Arduino. In the case of the Driver board that comes with the Make:it Robotics Starter Kit, not all of the port pins are used.
So if we want to add some new sensors or external devices, like Wifi communications to your robot, the extra port pins are available to do so. These extra pins are not documented anywhere except on the Schematic. So this blog post will show the Driver board image and the schematic image and map these available port pins so everyone see where they are on the Driver board.
Above is the image with the port pins marked in red on the Driver board, and an image of the same header pins from the schematic:
One method that is common on printed circuit boards (PCB) is to label the connections.
If you look at the schematic and closely on the Driver board you can see some of these labels. Note some of the labels are covered up by the actual black female header port pin sockets. You will just have to make an educated guess by comparing these ports with other pins where the labels are actually visible.
Notice on the Driver board image, the upper left header pins, marked in red, If you look closely you can see the soldered male pins that are on the bottom of the driver board. These pins are also shown on the schematic. Notice that these pins are attached to the female header sockets on the schematic by a single black line.
On the schematic the female header pin sockets are labeled A, B, C, and D. You should have no trouble in matching these header pin sockets, on the driver board to the ones shown in the schematic. Remember in the earlier blog post, “Make:it Robotics Starter Kit – Software Part 2″ we used pins 4 and 5 so we could send our sensor data to our software serial port and then on to our computer.
By looking at the schematic I was able to determine that pins 4 and 5 are extra pins not used by the driver board. Notice that in section A on the schematic that all pins, upper left bank, are used, so there are no extra pins that we can use in this section for data port pins, But the pins marked 3.3 V, 5 V and GND can be used to power sensors or devices that we want to connect to any available port pins in section B and D. If we look at section B, we can see that pin A0 is being used. The A pins are analog pins, All other pins on the Arduino are digital pins. Google the difference if you need an understanding.
That means that pins A1 – A5 are not being used and we could use these analog pins for our own modifications to our robot. Also look at section C. Notice that all port pins are being used in section C. So we cannot use these port pins for our own use. Look now at section D, Notice that port pins 2 and 3 are being used, in fact port pins 2 and 3 are being used to communicate between the processor on the driver board to the Arduino. The rest of the port pins 4 – 7 are available for use to use.
By looking at the schematic, port pins 1 and 2 appear to be not used on the driver board. Remember the driver board is a shield and plugs directly into the Arduino. On the Arduino pins 1 and 2 are used to communicate to the outside world using the built in hardware serial port. So we normally do not want to use port pins 1 and 2 on the Driver board.
More to come.