smc01a user guide.cdr
Contents
1. higher than 16 volts or if you don t care about size use the larger capacitor Which connector should I use A straight connector and a right angle connector are provided in the kit It is up to you which you choose to use you can also solder motor leads directly into the PCB holes and avoid using a connector altogether Assembly Instructions Caution The components U1 U3 can be damaged by static electricity Ground yourself touch a water pipe or the metal frame of a piece of electrical equipment before handling these components and avoid touching their leads Once assembled the motor controller can be stored safely in the conductive bag in which the kit is packaged Insert the 8 pin socket from the top side of the PCB in the area indicated U1 and solder On one side of the socket is a notch that should be aligned with the notch on the PCB drawing The socket protects the PIC microcontroller from being damaged during soldering Solder the 16 pin socket in the area indicated U2 Make sure to align the notch on the socket with the notch on the PCB drawing The socket allows you to replace the motor driver chip if it ever breaks 2001 http www pololu com 4 Pololu Pololu 2001 http www pololu com Next add the tantalum capacitor C2 You may need to bend the leads to2. make them straight so that they will fit The capacitor is polarized which means it must only go in one way Make sure the side labeled with a and a stripe goes into the hole that is also marked with a If the PCB is oriented as shown in the diagram the lower hole is for the positive lead Now add the voltage regulator U3 Make sure the device is oriented as shown on the silkscreen drawing with the flat side facing the outside of the PCB Caution The voltage regulator can be damaged by static electricity In this step add your choice of electrolytic capacitor for Cl The larger capacitor is necessary if you want to run your motors off of a 24 volt power source and you should use it if you don t care about the size of the completed motor controller The electrolytic capacitors are polarized but this time the stripe identifies the negative terminal Also the positive lead is longer Make sure to match up the positive lead with the appropriate hole in the PCB Next solder in your choice of connector You can use either the straight or the right angle female header provided in your kit or use your own connector If you prefer having leads soldered directly to the PCB you can do so now or wait until you have the leads ready and available Finally insert the two integrated circuits ICs U1 and U2 into their sockets Make sure that you plug them in so that the notches on the ICs match the notches on the PCB out
3. to run your motors off of a 12 volt battery You will also need an independent power supply for the motors if you want to use a personal computer as the robot controller In that case you might use a battery for the motor supply and use a wall outlet for the PC supply Connect the pin to the positive terminal of the motor supply this terminal may connect only to the motor controller or it may connect to any other device powered by that supply Warning the supply voltage may not exceed 16 volts or 25 volts depending on which capacitor you chose for C1 instep 5 ofassembly rm Reset Input The reset input is optional but you may need to use it to ensure that spurious signals sent when your robot controller turns on do not cause the motor controller to detect the baud rate incorrectly Connect this pin to a 0 5V digital output on your robot controller The line should normally be kept high 5V but bringing it low to OV for at least 2 microseconds resets the motor controller to its initial state all motors off waiting for its first serial command Serial Input Use a pin on your robot controller that can be used as a TTL level asynchronous serial output Serial data can be sent down this line 8 bits at a time with no parity bit at any rate between 1200 and 19200 baud Once you choose a baud rate you cannot change it until the motor controller is reset Important note unlike RS 232 serial line
4. 2CS508A N U3 Microcontroller U2 LM2931 and Socket SN754410 5 volt Regulator Dual H Bridge and Socket 2001 http www pololu com 2 Pololu Contacting Pololu You can check the Pololu web site at http www pololu com for latest information about the motor controller including color pictures application examples and troubleshooting tips We would be delighted to hear from you about your project and about your experience with our motor controller You can contact us through our online feedback form or by email at support pololu com Tell us what we did well what we could improve what you would like to see in the future or anything else you would like to say How to Solder You need a soldering iron and diagonal cutters to assemble the motor controller The green printed circuit board PCB is the base that holds the components together and establishes the necessary electrical connections The PCB has two sides a top side or component side which has white silkscreen markings and a bottom side or solder side Insert the components 1 solder soldering iron from the top side and solder them on the solder solder side In general you should insert and solder the components so that bottom L PCB they are as close as possible to the PCB All components in this kit except for top Ln voltage regulator U3 should be flush 2 check with the PCB After soldering trim fee good excess l
5. Dual Serial ou Motor Controller User s Guide Contents Safety Warning Parts List Contacting Pololu How to Solder Assembly Instructions Connecting the Motor Controller Using the Motor Controller How the Motor Controller Works Description and Specifications 2001 BL http www pololu com SMCO 1 A AS Important Safety Warning This kit is not intended for young children Assembly of this kit requires high temperature soldering and the use of sharp cutting tools Some included components may become hot leak or explode if used improperly Pololu strongly recommends that you wear safety glasses when building or working with any electronic equipment Children should use this kit only under adult supervision By using this product you agree not to hold Pololu liable for any injury or damage related to the use or to the performance of this product This product is not designed for and should not be used in applications where the malfunction of the product could cause injury or damage Parts List The following components are the motor controller parts Make sure to verify that all components are included and that you know which component is which Each component is labeled with its reference number and description There are 11 parts in the kit including the PCB A Cl C2 CONNECTOR PCB Electrolytic Tantalum 8 pin female Printed Circuit Capacitor Capacitor header Board 2 options 2 options Ul PIC1
6. ait for 20 ms 0 02 seconds before sending the next command When the first loop ends the motor is set to its full speed of 127 The second loop on lines 8 11 slows the motor back down by sending speeds from 127 down to 0 The next two loops on lines12 19 then repeat the process except for the parameter value of 1 in byte three which causes motor to spin forward 1 speed var byte 2 low 15 reset motor controller 3 high 15 4 for speed 0 to 127 5 serout 14 32 80 0 0 speed 6 pause 20 7 next 8 for speed 127 to 0 9 serout 14 32 80 0 0 speed 0 pause 20 i next 2 for speed 0 to 127 3 serout 14 32 S80 0 1 speed 4 pause 20 5 next 6 for speed 127 to 0 7 serout 14 32 S80 0 1 speed 8 pause 20 9 next 2001 http www pololu com 10 Pololu How the Motor Controller Works The motor controller uses H bridges to turn motors forward and backward see the dotted H in the left figure H bridges have four switches which are turned on in pairs to allow current to flow into the motors in both directions as shown below In the left figure all four switches are open and the motor is turned off When switches 1 and 4 close the motor turns in one direction when switches 2 and 3 close the motor turns the other way Integrated circuit U2 contains two H bridges allowing bidirectional control of two motors PANA Vhs mia o w y pe a cae ty a A technique called pulse width modulation PWM is used t
7. aiting for the first serial command You do not need to reset the motor controller to use it successfully However you may need to reset the motor controller to ensure that spurious signals sent when your robot controller turns on do not cause the motor controller to detect the baud rate incorrectly Controlling Multiple Motor Controllers with One Serial Line To control a particular motor you must specify its motor number in command byte 3 For all motor controller boards motor M1 responds to commands for motor number 0 and M2 responds to commands for motor number 1 To control more than two motors with a single serial line you need to use motor numbers 2 through 63 Motor controllers that are not specially ordered respond to numbers 2 and 3 you need to order specially programmed motor controllers to use motor numbers 4 through 63 For example to control six motors independently you need three motor controller boards each with different motor numbers All three motor controllers respond to commands for motor numbers 0 and 1 For controlling the six motors independently use motor numbers 2 3 4 5 6 and 7 The exact numbers depend on which motor numbers you request when you specially order additional motor controllers You can individually control up to 62 motors at a time with a single serial line using 31 motor controllers one with the default program and 30 that are specially programmed 2001 http www pololu com 9 Po
8. but the pins go positive when the controller receives a forward command If you find out that your motors turn in different directions than you expect you can flip the wiring or just switch the forward and reverse commands on your robot controller program Atypical setup is shown in the diagram below Keep in mind that the wiring you use for the motor outputs and power connections should be capable of conducting several amps We recommend using at least 26 gauge wire remember smaller numbers mean bigger wires SMCOIA a OUTI RESET OUT2 CONTROL eeeueuegg SO NINO EES 2001 Pololu http www pololu com Using the Motor Controller To set the speed and direction of a motor send a four byte command with the following structure to the motor controller s asynchronous serial input labeled 2 on the PCB start byte 0x80 device type 0x00 motor and direction motor speed You must send the fourbyte command eight bits at a time with no parity bit at a constant baud rate ranging from 1200 to 19200 baud The serial bits must be non inverted meaning that a zero is sent as a low voltage and a one is sent as a high voltage as shown LSB MSB in the diagram to the right The PC connection 10011010 circuit on the previous page corrects the inverted signal coming out of PC serial ports Commands OV sent to the serial input must conform to the above ZN A format
9. described in detail below or else the motor start bit stop bit controller and other devices connected to the serial line may behave unexpectedly This motor controller interface protocol is compatible with other Pololu serial devices such as our servo controller so you can control multiple Pololu serial devices on a single line 5V The Four byte Motor Controller Command Byte 1 Start Byte This byte should always be 0x80 128 in decimal to signify the beginning ofa command The start byte is the only byte with the highest bit bit 7 set and it alerts all devices on the serial line that a new command is being issued All succeeding bytes sent down the serial line must have their highest bit cleared to zero Byte 2 Device Type This byte identifies the device type for which the command is intended and it should be 0x00 for commands sent to motor controllers All devices that are not SMCO1A dual motor controllers ignore all subsequent bytes until another start byte is sent Byte 3 Motor Number and Direction This byte bit7 bit O has three parts as shown in the diagram to the right Olx Ix x x x Ix 1x Bit 0 specifies the direction of the motor Set s this bit to 1 to make the motor go forward clear bit 0 direction the bit to make it go backward 1 forward 0 reverse Bits 1 6 specify the motor number If you are using only two motors per serial line
10. eads with diagonal cutters N Mae bad To solder heat a component lead and the PCB pad and then apply solder until the Fania be solder flows onto both the lead and the 3 trim leads pad Ifthe solder beads up on the lead or A on the pad the connection is bad so you should apply more heat However be tD careful not to damage any components through overheating 2001 http www pololu com 3 Pololu Assembly Options You can assemble the motor controller in several ways so before you begin there are three choices you must make The options concern the size of the assembled motor controller You can insert the various components into the PCB without soldering to help determine which options are best for you Should I use IC sockets for U1 and U2 The sockets are not necessary and not using them will make your motor controller slightly smaller Not using them however will make it much more difficult to replace the ICs if they are damaged and also make it possible for you to damage the devices while soldering We strongly recommend using the sockets Which C1 option should I use Two electrolytic capacitors are provided in the kit The larger capacitor is rated for 25 volts whereas the smaller one is rated for 16 volts These ratings limit the voltage you can apply to the motor controller and thus limit the maximum voltage with which you can drive the motors If you want to drive the motor with voltages
11. l signals into motion However the power requirements of actuators electrical devices capable of producing motion are typically so high that normal digital circuitry cannot drive them In addition precise motion control requires constantly changing the signals sent to the actuators leaving the control circuitry with little time to attend to other tasks The Pololu motor controller bridges the gap between robot controllers and power hungry actuators Using one serial output from your robot controller you can independently set each of two small DC motors the kind typically found in remote control cars and motorized toys to go forward or backward at any of 127 different speeds To control additional motors you can connect multiple motor controllers to the same serial line The motor controller is compatible with the Pololu Servo Controller so you can control an almost unlimited number of motors and servos with one serial line Because of its small size the motor controller can fit almost any robot design Specifications POB BiG neiise 1 00 x0 85 Motor POMS ccccsscncctsnvadecacsennes 2 SCC OS ac sacncnse craetuseerneercccetnens 127 forward 127 backward and off Maximum current 05 1 A per motor continuous Supply Voltaeescccccicinesceess 5 6 25 V Data VOUA GG ccatosceceesraptrectilece Oand5 V PWM frequency 600 Hz Serial baud rate ccceee 1200 19200 automatically detected 2001 http www polo
12. line Do not solder the ICs to the sockets If you soldered the sockets in backwards it doesn t matter as long as the actual component is oriented correctly Be careful the ICs are static sensitive so take appropriate precautions and avoid touching their leads You may need to bend some of the leads to make them fit in the sockets if so hold the plastic body of the IC and push the pins gently against a flat surface one row at a time Connecting the Motor Controller There are eight pins on the bottom of the motor controller for connecting it to the rest of your system A closeup of the bottom of the PCB is shown to the right in case you have a hard time reading the silkscreen on your board The eight pin labels and the corresponding functions are LABEL FUNCTION shown in the table ground OV positive supply 5 6 25V reset serial control input motor 1 negative output M1 motor 1 positive output M2 motor 2 negative output M2 motor 2 positive output Connecting Power Warning connecting power incorrectly can cause some components to explode Connect M1 the ground pin to a ground terminal on your robot controller If you have a separate power supply for just the motors make sure that you connect the negative terminal ofthat supply to the same ground This situation may arise if for example you want to run your robot controller off of a 9 volt battery and you want
13. lolu Example BASIC Stamp II Program This program which can run ona BASIC Stamp II controller makes motor 1 gradually speed up then slow down then speed up in the other direction and then slow down again For the code to work pin 15 must be connected to the reset input 1 and pin 14 must be connected to the serial input 2 The interface code should look similar in other programming languages the description below should help you in understanding the code and ifnecessary in translating it to other languages On line 1 the 8 bit variable speed is declared for later use The motor controller is then reset by a low going pulse on pin 15 lines 2 and 3 The first for loop on lines 4 7 causes motor 1 to gradually speed up The serial output is created by the serout statement on line 5 The first parameter 14 specifies the pin number through which to send the serial signal The next parameter 32 sets up the serial characteristics to be 8 bits with no parity non inverted at a baud rate of 19200 The four numbers in square brackets are the data to be sent and they correspond to the four control bytes for the motor controller The first two bytes should always be 80 and 0 The second 0 makes motor 1 go backward The speed variable which increases every time through the loop is the only part of the command that changes and that is what makes the motor gradually speed up The pause statement on line 6 causes the program to w
14. lu com 12 Pololu
15. o control the speed of the motors The microcontroller U1 is a little computer that controls the H bridge switches It turns the switches on and off very rapidly 600 times per second and varies the percentage of the time that the switches are on to achieve the speed set by the serial interface For a higher speed the switches are on a larger fraction ofthe time than for a slower speed At the maximum speed of 127 the switches are left on The momentum of the motor shaft keeps the shaft spinning at a constant speed that can be varied smoothly over all 127 different speeds J J i U3 and the capacitors provide a steady 5V power supply for the microcontroller which cannot run at the full motor voltage provided to the board at the and pins The complete schematic diagram of the motor controller is shown below u3 LM2931 e VIN VOUT GND Ul PIC12C508A U2 SN754410 6 8 vss Gri 1a vcc l loLe t vec e2 PB 4 on L2EN 110 3 MCLR GP5 7 15 3A 3 4EN 3 210 GP4 GPO A 4A VMOT 3 GND 2Y O 5 3 M1 Ej c2 T GND 1Y JA O 4 T 100 To 99 73 GND AY ir TO M2 e GND 3Y Oj 4 2001 http www pololu com 11 Pololu The Pololu Dual Serial Motor Controller For a robot to interact with its environment it must be able to convert electrica
16. s the standard for serial ports used to connect devices to personal computers this line uses TTL voltages between 0 and 5 volts The higher voltages used on RS 232 lines will damage the motor controller If you need to convert RS 232 levels to TTL levels you will need to use a level converter such as the MAX220 made by Maxim You could also use the simple circuit shown at the top of the next page When building circuits that connect to a PC be especially careful because you could potentially destroy the PC s serial port Before attempting to connect your own electronics to a computer make sure you know what you are doing 2001 http www pololu com 6 Pololu DB9 serial gt josy circles port connector a off C2 iy 4 7k 5 R2 to serial 2 m gt control a input 2 Raid lt 3 indicate pads oo that are connected to 5V which you can use with the circuit shown on the left to ground The above diagram shows a simple circuit for connecting the motor controller to a PC serial port You will need to connect one side of resistor R1 to a 5V supply which is available on the PCB at the points indicated on the figure to the right You can solder a wire onto one ofthe pads but make sure that the wire touches only the intended pad Connecting the Motors Connect one or two motors to the pins labeled M1 and M2 You probably don t need to worry too much about the polarity
17. you can IL bits 1 6 motor use the default values of 0 for motor M1 and 1 for number motor M2 Ifyou want to control more thantwo _________ bf 7 always 0 motors use numbers in the range of 2 to 63 as described in the section Controlling Multiple Motor Controllers with One Serial Line 2001 http www pololu com 8 Pololu Byte 3 Motor Number and Direction continued Bit 7 must be cleared since this is not a start byte To obtain the complete byte 3 value from a motor number and a direction multiply the motor number by 2 and add 1 if the direction is forward For example to make motor 5 go forward byte three should be 5 x2 1 11 To make motor 1 go backward byte 3 should be 1 x2 2 Two efficient ways to multiply by 2 in a microcontroller program are shifting left by one digit or adding the motor number to itself Byte 4 Motor Speed The most significant bit must be zero since this is not a start byte and the remaining seven bits are available for specifying the speed The possible range of values for byte 4 is thus 0x00 to 0x7F 0 to 127 decimal 0x00 turns the motor off and 0x7F turns the motor fully on intermediate values correspond to intermediate speeds Resetting the Motor Controller The motor controller s optional reset line should normally be kept high at 5V Pull the reset line low to OV for at least 2 microseconds to reset the motor controller to its initial state all motors off w
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