Sabertooth 2x25 User’s Guide July 2007 Input voltage: 6-24V nominal, 30V absolute max. Output Current: Up to 25A continuous per channel. Peak loads may be up to 50A per channel for a few seconds. Recommended power sources are: • • • • 5 to 18 cells high capacity NiMH or NiCd 2s to 6s lithium ion or lithium polymer. Sabertooth motor drivers have a lithium battery mode to prevent cell damage due to over-discharge of lithium battery packs.
Features Mixed and independent options: Sabertooth features mixed modes designed especially for differential drive robots, where two motors provide both steering and propulsion. It also has independent options in all operating modes. This is useful for if you have two motors to control, but they aren’t necessarily being used to drive a differential drive robot. The motors do not need to be matched or even similar, as long as they both are within Sabertooth’s operating limits.
Hooking up the Sabertooth motor driver All connections to the Sabertooth are done with screw terminals. This makes it easy to set up and reconfigure your project. If you’ve never used screw terminal connections before, here is a quick overview. Step 1: Strip the wire which you are using approximately ¼” The wires may be 12 gauge to 30 gauge. Use thicker wire for high current applications.
Battery Terminals B+ and BThe battery or power supply is connected to terminals B- and B+. B- connects to the negative side of the battery (usually black.) B+ connects to the positive side of the battery The battery connects to terminals B+ and B(usually red or yellow.) It is usually best to connect the battery through a connector instead of directly to the motor driver. This makes it easy to unplug the battery for charging, and prevents plugging in the battery backwards.
Motor Terminals Motor 1 is connected to terminals M1A and M1B as shown below. If the motor runs in the opposite way that you want, you may reverse the motor wires to reverse rotation. Motor 2 is connected to terminals M2A and M2B The motors connect to terminals M1A/B and M2A/B Signal Input Terminals S1 and S2 The input signals that control the Sabertooth are connected to terminals S1 and S2.
Power terminals 0V and 5V The 0V and 5V connections are used to power and interface to low-power control circuits. The 5V connection is a 5v power output. This is useful for supplying power to lowcurrent devices, such as a The 5V terminal can be used to power small loads, like a potentiometer or a radio potentiometer or a radio receiver. The 0V signal must be receiver. The 5v terminal is connected to the ground of the device generating the input capable of supplying 100 signal.
Status and Error LEDs Sabertooth 2x25 has three indicator LEDs. The blue LED marked Status1 is used to communicate various information about the current state. In most cases Status1 acts as a power indicator. In R/C mode, it glows dimly if there is no RC link present and brightly if there is an RC link. The blue LED marked Status2 is only used in lithium mode. It blinks to indicate the number of lithium cells detected. The red Error LED illuminates if the Sabertooth has detected a problem.
Operating Modes Overview Mode 1: Analog Input Analog input mode takes one or two analog inputs and uses those to set the speed and direction of the motor. The valid input range is 0v to 5v. This makes the Sabertooth easy control using a potentiometer, the PWM output of a microcontroller (with an RC filter) or an analog circuit. Major uses include joystick or foot-pedal controlled vehicles, speed and direction control for pumps and machines, and analog feedback loops.
Lithium cutoff: Switch 3 of the DIP switch block selects lithium cutoff. If switch 3 is in the down position as shown the Sabertooth will automatically detect the number of series lithium cells at startup, and set a cutoff voltage of 3.0 volts per cell. The number of detected cells is flashed out on the Status LED. If the number of cells detected is too low, your battery is in Lithium Cutoff enabled a severely discharged state and must be charged before operation.
Mode 1: Analog Input Analog input mode is selected by setting switches 1 and 2 to the UP position. Switch 3 should be either up or down, depending on the battery type being used. Inputs S1 and S2 are configured as analog inputs. The output impedance of the signals fed into the inputs should be less than 10k ohms for best results. If you are using a potentiometer to generate the input signals, a 1k, 5k or 10k linear taper pot is recommended. In all cases, an analog voltage of 2.5V corresponds to no movement.
Note on using filtered PWM in Analog Mode If you are using a filtered PWM signal from a microcontroller to generate the analog voltage, an R/C filter with component values 10k ohms and at least .1uf is recommended as shown in Figure 4.1. Using a larger value Figure 4.1: Filtered PWM filter capacitor such as 1uf or 10uf will result in smoother motor operation, at a cost of slower transient response. A PWM frequency higher than 1000Hz is recommended.
Mode 2: R/C Input R/C input mode is used with a standard hobby Radio control transmitter and receiver, or a microcontroller using the same protocol. R/C mode is selected by setting switch 1 to the DOWN position and switch 2 to the UP position. If running from a receiver, it is necessary to obtain one or more servo pigtails and hook them up according to figure 5.1. If there are only motor drivers being used it is acceptable to power the receiver or microcontroller directly from the Sabertooth as shown.
Switch 6: R/C Mode/Microcontroller mode select If switch 6 is in the UP position, then the Sabertooth is in standard R/C mode. This mode is designed to be used with a hobby-style transmitter and receiver. It automatically calibrates the control center and endpoints to maximize stick usage. It also enables a Timeout Failsafe, which will shut down the motors if the Sabertooth stops receiving correct signals from the receiver.
Mode 3: Simplified Serial Mode Simplified serial uses TTL level single-byte serial commands to set the motor speed and direction. This makes it easy to interface to microcontrollers and PCs, without having to implement a packet-based communications protocol. Simplified serial is a one-direction only interface. The transmit line from the host is connected to S1. The host’s receive line is not connected to the Sabertooth. Because of this, multiple drivers can be connected to the same serial transmitter.
Option 1: Standard Simplified Serial Mode Serial data is sent to input S1. The baud rate is selected with switches 4 and 5. Commands are sent as single bytes. Sending a value of 1-127 will command motor 1 Sending a value of 128-255 will command motor 2. Sending a value of 0 will shut down both motors.
Mode 4: Packetized Serial Mode Packetized Serial uses TTL level multi-byte serial commands to set the motor speed and direction. Packetized serial is a one-direction only interface. The transmit line from the host is connected to S1. The host’s receive line is not connected to the Sabertooth. Because of this, multiple Sabertooth 2x25 motor drivers can be connected to the same serial transmitter.
Address Byte Configuration: Address bytes are set by switches 4, 5 and 6. Addresses start at 128 and go to 135.
Commands: The command byte is the second byte of the packet. There are four possible commands in packetized serial mode. Each is followed by one byte of data 0: Drive forward motor 1 (decimal 0, binary 0b00000000, hex 0h00) This is used to command motor 1 to drive forward. Valid data is 0-127 for off to full forward drive. If a command of 0 is given, the Sabertooth will go into power save mode for motor 1 after approximately 4 seconds.
6: Drive motor 1 7 bit (decimal 6, binary 0b00000110, hex 0h06) This command is used to drive motor 1. Instead of the standard commands 0 and 1, this one command can be used to drive motor 1 forward or in reverse, at a cost of lower resolution. A command of 0 will correspond to full reverse, and a command of 127 will command the motor to drive full forward. A command of 64 will stop the motor. 7: Drive motor 2 7 bit (decimal 7, binary 0b00000111, hex 0h07) This command is used to drive motor 2.
Checksum: To prevent data corruption, each packet is terminated with a checksum. If the checksum is not correct, the data packet will not be acted upon. The checksum is calculated as follows: Checksum = address byte +command byte +data byte The checksum should be added with all unsigned 8 bit integers, and then ANDed with the mask 0b01111111 in an 8 bit system.
