STEVAL-IHM012V1 - Cordless drill evaluation board - Digi-Key
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1. UMO291 JT User manual STEVAL IHMO12V1 Cordless drill evaluation board Introduction This document contains cordless drill evaluation board information including jumper settings load connection and device and software features This evaluation board implements a traditional design solution detailing how the Chopper circuit controls a brush DC motor with a microcontroller as a driver The electronic driver with a Power MOSFET and microcontroller presented in this document is cost effective and easy for designers to implement This solution can be typically used in cordless tools shavers toys and machine tools Analog solutions are being progressively replaced by microcontroller designs even in low cost applications Their advantages include flexibility using less external components easy adaptation by simple software modifications and control components can be designed with a potentiometer October 2007 Rev3 1 18 www st com Contents UMO291 Contents 1 Block diagram of a single switch Chopper 4 1 1 Controller P de ke Ae Ee EE e e ee 4 1 2 Power MOSFET ipsae ANERE cee aoe A Wes ow P EAE RS eee ee eS 5 1 3 Power SUpDIV iso ET EE seb ioe ew ER eda ee eee ER REESE 5 1 4 Freewheeling diode scio crus reek bende dee Gel eek nie tee Sea ee 5 2 STEVAL IHMO12V1 evaluation board 0 000 c eee eee eee eee 6 3 Size optimization design procedure Llss 7 4 Application desig2. pe 78 95 Low signal amplitude EMNE NENN NNN i Latz PPP ERE ERE IE LU fi M 100ps 25MS s 400nsipt Chi 20 o DG 10V By M200us 128MS s 800nsipt A Ch2 1 987 A Ch2 198v mm pw 14 18 We have taken two cases one at duty cycle 60 and another at duty cycle 100 see Figure 8 Figure 9 Figure 10 and Figure 11 When the high current protection routine works the controller limits and forces the motor current to 7 A rms UM0291 Schematic 7 Schematic Figure 12 STEVAL IHMO12V1 evaluation board schematic Se ng uv 1 4 4 Battery supply 2 ca 65 ICCDATA Battery Charge i Ji ki f i i ICC clock gt E SE CONNECTOR Ke CCDATA CLKIN 2 pas HSAINLELKIN PEE PUM PAD HSVATPUIM Ki oe lt gt rius A Battery Charge BE E L n LJ Speed Regulation MESE PAS RESET usc n al Ng e m Ge E JB STD50NHO2L m are Dpack 10K SE zi E WE cce gt Isensing T e ik T War 1 p ae 8 Bill of material BOM Table 1 Bill of material Manufacturer s Value generic ordering code Index Qty Reference part number Package Manufacturer orderable part number 1 3 C1 C2 C5 100 nF 25 V 5 SMD_0805 2 1 C3 100 pF 50 V 5 SMD_0805 3 1 C4 1 uF 16 V 10 SMD 0805 4 1 DZ1 5 1 V 1 2W SMD
3. e High current protection Torque limitation When the current of the motor reaches the maximum handling current Imax the Controller disables the PWM output regardless of the pot position In this case the LED turns on As soon as the current becomes less than Imax the control switches back to the user and the LED turns off ky UM0291 Block diagram of a single switch Chopper Note 1 2 1 3 1 4 In this evaluation board we have chosen the ST7FULTRALITE which is a very small and less expensive microcontroller available in DIP8 DFN8 and SO8 packages e Extended 40 C to 125 C temperature range Fast 10 bit ADC 8 bit timer with Watchdog 12 bit ART 6 I Os External and internal clock management 5 power saving modes including Autowakeup from Halt The microcontroller has still one O ADC PIN free for other uses For example this free pin could be used to change through a potentiometer the value of the threshold Imax in the high current protection The user can directly change the max handling Torque and the potentiometer emulates the mechanical clutch present in all electrical drills Power MOSFET With very low Rps on STripFET Power MOSFETs are suitable for high power applications such as cordless tools We have chosen the STD50NHO2L in D Pack package because this device can be driven directly by the ST7FULTRALITE Thus we can avoid using the Power MOSFET driver and can economize the size and costs of t
4. of companies Australia Belgium Brazil Canada China Czech Republic Finland France Germany Hong Kong India Israel Italy Japan Malaysia Malta Morocco Singapore Spain Sweden Switzerland United Kingdom United States of America www st com a 18 18
5. 1206 12 5 1 D1 LED SMD 1206 21 6 1 D2 STPS5L25B SMD DPAK ST STPS5L25B TR 7 1 D3 1N4148 SMD1206 21 8 2 J1 J2 CON2 Jumper a 15 18 References and related materials UMO0291 Table 1 Bill of material continued Manufacturer s Index Gty Reference Ke disais Package Manufacturer debi Noua number 9 4 J3 J4 J5 J6 CON1 FASTONF 10 pin strip header 10 1 J7 ICC Con dual in line2 54 mm pitch 11 1 Q1 STD50NHO2L SMD DPAK STMicroelectronics STD50NHO2LT4 12 1 R1 820 Q 1 SMD_0805 13 1 R2 100 Q 1 SMD_0805 14 1 R3 POT 10 kQ VRES18 15 1 R4 5 1 kQ 1 4 W 5 SMD_1206 16 1 R5 0 0593 W 17 1 R6 30 kQ 1 SMD_0805 18 1 R7 10 KQ 1 SMD_0805 19 1 R8 18 Q 1 SMD_0805 20 1 R9 68 Q 1 4 W 5 SMD_1206 21 1 R10 100 KQ 1 SMD_0805 22 1 R11 3 3 KQ 1 SMD_0805 23 1 U1 ST7FLITEUS5 SO8 ST ST7FLITEUS5M6 9 References and related materials 16 18 It is possible to find additional information in the following website www st com e Datasheet ST7FLITEUSBS datasheet STD50NHO2L datasheet STPSBL25B datasheet e Application note AN1703 Guidelines for using ST S Power MOSFET SMD packages AN238B5 Power dissipation and its linear derating factor silicon Limited Drain Current and pulsed drain current in Power MOSFETs AN414 Controlling a brush DC motor with an ST6265 Microcontroller UM0291 Revision hi
6. AIMS ANY EXPRESS OR IMPLIED WARRANTY WITH RESPECT TO THE USE AND OR SALE OF ST PRODUCTS INCLUDING WITHOUT LIMITATION IMPLIED WARRANTIES OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION OR INFRINGEMENT OF ANY PATENT COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT UNLESS EXPRESSLY APPROVED IN WRITING BY AN AUTHORIZED ST REPRESENTATIVE ST PRODUCTS ARE NOT RECOMMENDED AUTHORIZED OR WARRANTED FOR USE IN MILITARY AIR CRAFT SPACE LIFE SAVING OR LIFE SUSTAINING APPLICATIONS NOR IN PRODUCTS OR SYSTEMS WHERE FAILURE OR MALFUNCTION MAY RESULT IN PERSONAL INJURY DEATH OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE ST PRODUCTS WHICH ARE NOT SPECIFIED AS AUTOMOTIVE GRADE MAY ONLY BE USED IN AUTOMOTIVE APPLICATIONS AT USER S OWN RISK Resale of ST products with provisions different from the statements and or technical features set forth in this document shall immediately void any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever any liability of ST ST and the ST logo are trademarks or registered trademarks of ST in various countries Information in this document supersedes and replaces all information previously supplied The ST logo is a registered trademark of STMicroelectronics All other names are the property of their respective owners 2007 STMicroelectronics All rights reserved STMicroelectronics group
7. M AT OVF routine See flowchart in Figure 6 Figure 6 Main programming flowchart Ports init ADC init AR timer init Variables init v While o 0 Enable 1 Speed pot position v Reading Battery Level 8856 lt 90 Battery Voltage full LED LED LED Fast Flashing Turn off Slow Flashing Disable Motor control Y routine zi Safe Batt 1 Safe Batt 0 44 Y Motor Can t work Enable 0 J 12 18 ky UM0291 Software 5 2 pwm_ar_timer_12bit c The AT timer in OF mode is used as the main time counter This interrupt is handled in the AR TIMER OF Interrupt routine in the pwm ar timer 12bit module This module generates the PWM control signal to the frequency of 15 kHz implements the high current protection routine and software counter incrementing time base 68 usec See Figure 7 Figure 7 Flowchart of the pwm ar timer 12bit module pwm ar timer Update DCRO register Safe batt Count Set Duty Cycle Lt Current Sensing Reading lt Imax 2Imax s 2 Current Sensing Reading High current protection mode Zero PWM Signal y Imax LED Turn ON Enable 1 In the high current protection routine two reading operations in the same PWM OVF interrupt are performed to detect an eventual over current eve
8. al designer chooses to change the Power MOSFET to increase current capabilities 10 18 UM0291 Software 5 Note Note Software The software is written in C language structured and commented The main functions necessary for the proper operations of the evaluation board can be found in the following c files e main c e pwm ar timer 12bit c The follow h files have to be included e st7fliteus5 h e pwm ar timer 12bit h e Utility The option byte set in this project is shown in Figure 5 Figure 5 Option byte for STEVAL IHMO12V1 firmware Value F0 2B Name Description SECO Sector 0 Size 0 5k FMP_R Read out Protection OFF FMP Ww WRITE Protection OFF CKSEL Internal RC as startup clock LVD Highest Voltage Threshold V 1 WDG Sw Software WDG HALT Reset when Halt PROGRAM MEMORY A OPTION BYTE the overall code with the actual function is very small almost 213 Byte The firmware parameters are set for the 7 2 DC brush motor if the designer wishes to change the motor he must change the firmware parameters in the file utility h Parameters e Setting DC motor type multiplied by 10 i e 7 2 DC brush motor define Motor Type 72 e Setting Isafe maximum handling current in load conditions The values must be multiplied in Amper by 10 In the firmware the default values are 8 A so we have define Isafe 80 we have another parameter Imin it has bee
9. aluation board schematic llle 15 3 18 Block diagram of a single switch Chopper UMO0291 1 1 4 18 Block diagram of a single switch Chopper Brush DC motors can be driven in voltage mode since the motor speed is proportional to the supply voltage The chopper is driven by a high frequency PWM signal Controlling the PWM duty cycle is equivalent to controlling the motor voltage which in turn adjusts directly the motor speed A typical block diagram of a DC single switch Chopper is shown in Figure 1 Figure 1 Block diagram of a single switch Chopper POWER SUPPLY commands sense resistor Controller We use a microcontroller to have a flexible controller and to implement the control algorithm because an analog IC s functionality is tied to its application and the designer is limited to fixed device functions Thus we generate the PWM signal and implement some safety protections Main features implemented e DC motor speed regulation system Through the pot you can change the duty cycle of a PWM signal at 15 kHz POT zero position NO PWM signal POT increase position Duty Cycle 13 100 e Battery voltage check There are 3 states managed by the controller through the reading Level Battery Charged LED turn off Low LED Slow flashing warning threshold 9096 of the nominal voltage Discharged Fast flashing the motor cannot work threshold 88 of the nominal voltage
10. der normal conditions these jumpers must be present before the input voltage is connected With easy adjustments the STEVAL IHMO12V1 can drive DC brush motors 7 2 18 V The maximum power range used on the evaluation board depends on the motor driven maximum handling current and relative Power MOSFET mounted on the board see Section 4 Application design procedure This evaluation board is set up to work with a 7 2 DC brush motor Imax is set at 8 A the supply current for the microcontroller is obtained from the input voltage The Zener regulator circuit in this application is designed to ensure the minimum voltage for the microcontroller operations also if the battery voltage is the minimum allowed UM0291 Size optimization design procedure Note Figure 2 STEVAL IHM012V1 evaluation board picture 2 7577 STEVAL IHNO12V Size optimization design procedure This demo board implements a general solution to drive a low voltage DC brush motor The application is optimized for cordless hand tools drill saw screwdriver The size is small enough to be inserted directly in the tool Figure 2 To minimize the size of the board The ICC connector is not needed in the manufacturing process either because the microcontroller can be already programmed before assembling The potentiometer emulates the push button of the cordless drill To be replaced by the potentiometer on off switch on the tool The Pow
11. er MOSFET and diode can be mounted near the motor where the air flux cools them down The UltraLite is available in DFN8 package Less than 16 mm Following this procedure the optimal design achieved is approximately 20x15 mm The demo board is implemented only on the top to reduce the manufacturing cost 7 18 Application design procedure UM0291 4 4 1 8 18 Application design procedure This evaluation board can be configured for different DC brush motors 7 2 V 18 V here we have an example of design procedure for 7 2 V DC brush motor If the user wants to configure the Evaluation board for other motors there are the following adjustments to do e Zener regulator circuit Rg e Sensing resistor Rgens e Power MOSFET evaluating the operating junction temperature Zener regulator circuit The power supply is shown in Figure 3 The input current lw can be expressed by the following equation Equation 1 i MS a IN Rs where Vg Supply voltage VZD the voltage drop V across the Zener diode and Rs the resistor Figure 3 Zener regulator circuit DIV EH G Vout D A Equation 2 lin Laner MiN lout where lour is the maximum absorbed current by the microcontroller We can estimate lout considering that the active on chip peripherals are working together and thus lour 8 mA The current to hold the Vz 5 1 V is Gene min 5 MA see datasheet In the N
12. ere tests for electronic drills is to evaluate the transistor s performance with the rotor blocked In this case the rotor remains fixed for a minimum time of 20 seconds while the Power MOSFET runs at the maximum duty cycle at maximum RMS current in this case is fixed by the safety routine in the microcontroller Equation 6 2 PDrot Pl ng aere Rps on Joan Where li oAp maximum handling current by the motor The operating junction temperature is Equation 7 Ty Ta be ror PDroT 9 18 Application design procedure UM0291 Where Ta Ambient Temperature Hr vor Total thermal resistance The total power dissipation will be Equation 8 PDrot Rps on Loan 0 012 e BI 0 77W In the evaluation board the available copper area on PCB for heat dissipation is almost 400 mm This is shown in Figure 4 Equation 9 Haut sens 50 C W Figure 4 Rryy pcg Versus drain pad area for DPACK Rrus pcs VS drain pad area FR 4 2 oz copper board 120 100 Minimum recommended footprint Rthj PCB C W 8 ES 0 10 20x04 DU ao HO DH ww 100 Area mm The total thermal resistance is Equation 10 Dou ror Pru case Pru pen 2 5 50 52 5 C W Thus Equation 11 Ty Ta Rry_tor PDror 52 5 0 77 40 4 C In the worst case we can take Ta 40 C and Ty 80 is lower T jux 175 C The above consideration has to be done if the fin
13. he demo board see Figure 2 Main features see datasheet Rpgon 0 00120 0 5 V Id 50A Rrwu case 2 5 C W Thermal resistance Junction case Power supply To reduce board cost we have implemented the power supply with a Zener regulator circuit see Figure 3 Freewheeling diode For the freewheeling diode the STPS5L25B has been chosen and is available in DPACK packaging see Figure 3 We now have a more compact board in order to utilize the available area on PCB for heat dissipation 5 18 STEVAL IHMO12V1 evaluation board UMO0291 2 Note 6 18 STEVAL IHMO12V1 evaluation board The STEVAL IHM012V1 evaluation board was developed to demonstrate ST s solution for low end cordless tools such as cordless drills or screwdrivers but it can be a good starting point for designing all the applications where it need to drive a low voltage DC brush motor The board is shown in Figure 2 On the left side there are two connectors the mains connector for battery voltage supply On the right side there are two connectors the connector for the DC Brush motor speed adjustment pot That potentiometer emulates the standard push button mounting in the case of a cordless drill to regulate the rate of the motor e ICC connector and jumpers J1 and J2 Warning Before downloading firmware in the microcontroller ensure that jumpers J1 and J2 are NOT present before the input voltage is connected Un
14. iCd and NiMH batteries the cell voltage is 1 2 V and in discharge condition it must be more than 1 V to avoid damaging them We have to assure that the microcontroller is supplied with 5 V in all conditions and thus we have chosen Vg Vgmin 88 VNominal Of battery UMO0291 Application design procedure 4 2 4 3 So Rs will be Equation 3 Rg Vsmin m Vzp lzener MIN lout For the 7 2 cordless drill 6 cells we have chosen Vgmin 88 VNominai and thus Rg 68 Q Sensing resistor Rsens The value of the sensing resistor must be chosen to guarantee the right power dissipation at the maximum handling current and to guarantee at least 300 mV in order to read the motor current using the 10bit on board microcontroller ADC The evaluation board has been set and tested for a 7 2 DC brush motor The maximum current for the used motor is Imax 8 A It follows that Equation 4 Rgeng 0 05 Power MOSFET The choice of the Power MOSFET begins by choosing devices that can handle the required current given an adequate thermal dissipation path Here we have the equations for calculating the power dissipation of these MOSFETs and determining the temperature at which they operate To determine whether or not a Power MOSFET is suitable for that application we must calculate its power dissipation which consists mainly of resistive and switching losses Equation 5 PDror PDresistive PDswircHiNG One of the most sev
15. n procedure llll l l 8 4 1 Zener regulator circuit 224 wee eee ER EEPSQE REPE Tue ENSE EERPERES 8 4 2 Sensing resistor Rgens 2 2 eee eere 9 4 3 Powet MOSFET sccccserewiavee dee eewien ge e AE Ee E er 9 5 NS a setae ENEE OR QR Oe td e apa RO i ele CR 11 5 1 OEB sa vara cena RE een ee eee a awd a EEG EN ee eee ERRE DERS 12 5 2 pwm_ar_timer_12bit c 0 0 0 ee 13 6 ek EE EE 14 7 SchemiallG uuekesuue saxa NEEN E UR eae RR n 15 8 Bill of material BOM 000 e ee eee 15 9 References and related materials 16 10 REVISION history uacua dux x eee RR RR il e ee RR SA EN E 17 218 ky UM0291 List of figures List of figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Block diagram of a single switch Chopper 00 cece eee 4 STEVAL IHMO12V1 evaluation board picture 7 Zener regulator circuit essre rire at ukreniti Ea e a E A a a a a 8 Hui pcp Versus drain pad area for DPACK 10 Option byte for STEVAL IHMO12V1 firmware 11 Main programming flowchart 12 Flowchart of the pwm ar timer 12bit module 0 000 c eee eee eee 13 Duty cycle 60 in no load condition llli 14 Duty cycle 60 in blocked rotor 0 00 er 14 Duty cycle 100 in no load condition 000 eee 14 Duty cycle 100 in blocked rotor ee 14 STEVAL IHMO12V1 ev
16. n set to a value slightly higher than the current in no load conditions in order to be sure that the safe is set to a value greater than the minimum current drain by the motor e The default value is 3 A define Imin 30 11 18 Software UMO291 The working principle of using a Power MOSFET to drive DC brush motor is to change the duty cycle of the PWM control signal generated by the 12 bit autoreload timer AT inside the software Note Before downloading firmware in the microcontroller ensure that jumpers J1 and J2 are NOT present before the input voltage is connected Thus under normal conditions these jumpers must be present before the input voltage is connected See Figure 2 5 1 Main c The battery voltage check function and the Speed Pot reading are implemented in this module as described above The reading of the Speed Pot and Safe Battery routine are synchronized on the Overflow event OVF interrupt of the Auto reload timer through the enable flag Enable is true at the end of each OVF interrrupt The Speed Pot is read every 5 cycles look at variable count of the Auto reload timer The voltage battery is read every 10000 1 cycles look at the variable counter in standard mode and it will be read every 2000 1 cycles in battery safe mode Note in this way the Speed Pot reading and voltage battery reading won t be done in the same PWM period The value of duty cycle is updated in the PW
17. nt through the ADC analog input If the current signal is higher than threshold Imax the PWM output will be set to zero and the LED will be turned ON 13 18 Field tests UMO0291 6 Figure 8 Field tests We have plotted the PWM control signal waveform in blue and the current in the motor waveform in black when it runs in no load condition and in the blocked rotor condition We have some examples which show how the high current protection routine operates For these tests we used one 7 2 DC brush motor and set the software parameters to define Isafe 70 7 A define Imin 30 3 A Duty cycle 60 in no load condition Figure 9 Duty cycle 60 in blocked rotor Maat 7844 nt 4 848 C1 62854 Feat 16 24kHr DyCyc C2 55 81 Ch2 30v Bw 7 0664 Freq 02 1316kM pen 12 81kHz Low signal amplitude netz 27 6 Figure 10 Duty cycle 100 in no load Figure 11 Duty cycle 100 in blocked rotor condition 1 IN NNN NARA SEAN MARAB KANN AA IMax C1 3 448 d Maat 10 484 ingot 1364 N i AAA TA AM n WI Ini 495 EHIH NANI INAN d AU MAN positiiiitiiia Chi 204 Q
18. story 10 Revision history Table 2 Document revision history Date Revision Changes 19 Dec 2006 1 First issue 08 Jan 2007 2 Figure 2 changed 25 Oct 2007 3 Modified Figure 5 and Table 1 17 18 UMO0291 Please Read Carefully Information in this document is provided solely in connection with ST products STMicroelectronics NV and its subsidiaries ST reserve the right to make changes corrections modifications or improvements to this document and the products and services described herein at any time without notice All ST products are sold pursuant to ST s terms and conditions of sale Purchasers are solely responsible for the choice selection and use of the ST products and services described herein and ST assumes no liability whatsoever relating to the choice selection or use of the ST products and services described herein No license express or implied by estoppel or otherwise to any intellectual property rights is granted under this document If any part of this document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party products or services or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoever of such third party products or services or any intellectual property contained therein UNLESS OTHERWISE SET FORTH IN ST S TERMS AND CONDITIONS OF SALE ST DISCL
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