DRV8825 Stepper Motor Driver Carrier, High Current

$31.5 $58.91
The Pololu DRV8825 step­per motor dri­ver car­ri­er is a break­out board for TI’s DRV8825 microstep­ping bipo­lar step­per motor dri­ver. The mod­ule has a pinout and inter­face that are near­ly iden­ti­cal to those of the A4988 step­per motor dri­ver car­ri­ers, so it can be used as a high­er-per­for­mance drop-in replace­ment for those boards in many appli­ca­tions. The DRV8825 fea­tures adjustable cur­rent lim­it­ing, over­cur­rent and overtem­per­a­ture pro­tec­tion, and six microstep res­o­lu­tions (down to 1/32-step). It oper­ates from 8.2 – 45 V and can deliv­er up to approx­i­mate­ly 1.5 A per phase with­out a heat sink or forced air flow (rat­ed for up to 2.2 A per coil with suf­fi­cient addi­tion­al cool­ing).Fea­tures Sim­ple step and direc­tion con­trol inter­faceSix dif­fer­ent step res­o­lu­tions: full-step, half-step, 1/4‑step, 1/8‑step, 1/16-step, and 1/32-stepAdjustable cur­rent con­trol lets you set the max­i­mum cur­rent out­put with a poten­tiome­ter, which lets you use volt­ages above your step­per motor’s rat­ed volt­age to achieve high­er step ratesIntel­li­gent chop­ping con­trol that auto­mat­i­cal­ly selects the cor­rect cur­rent decay mode (fast decay or slow decay)45 V max­i­mum sup­ply volt­ageBuilt-in reg­u­la­tor (no exter­nal log­ic volt­age sup­ply need­ed)Can inter­face direct­ly with 3.3 V and 5 V sys­temsOver-tem­per­a­ture ther­mal shut­down, over-cur­rent shut­down, and under-volt­age lock­outShort-to-ground and short­ed-load pro­tec­tion4‑layer, 2 oz cop­per PCB for improved heat dis­si­pa­tionExposed sol­der­able ground pad below the dri­ver IC on the bot­tom of the PCBMod­ule size, pinout, and inter­face match those of our A4988 step­per motor dri­ver car­ri­ers in most respects (see the bot­tom of this page for more infor­ma­tion)Using the Driver Power connectionsThe dri­ver requires a motor sup­ply volt­age of 8.2 – 45 V to be con­nect­ed across VMOT and GND. This sup­ply should have appro­pri­ate decou­pling capac­i­tors close to the board, and it should be capa­ble of deliv­er­ing the expect­ed step­per motor cur­rent.Warn­ing: This car­ri­er board uses low-ESR ceram­ic capac­i­tors, which makes it sus­cep­ti­ble to destruc­tive LC volt­age spikes, espe­cial­ly when using pow­er leads longer than a few inch­es. Under the right con­di­tions, these spikes can exceed the 45 V max­i­mum volt­age rat­ing for the DRV8825 and per­ma­nent­ly dam­age the board, even when the motor sup­ply volt­age is as low as 12 V. One way to pro­tect the dri­ver from such spikes is to put a large (at least 47 µF) elec­trolyt­ic capac­i­tor across motor pow­er (VMOT) and ground some­where close to the board.Motor connectionsFour, six, and eight-wire step­per motors can be dri­ven by the DRV8825 if they are prop­er­ly con­nect­edWarn­ing: Con­nect­ing or dis­con­nect­ing a step­per motor while the dri­ver is pow­ered can destroy the dri­ver. (More gen­er­al­ly, rewiring any­thing while it is pow­ered is ask­ing for trou­ble.)Step (and microstep) sizeStep­per motors typ­i­cal­ly have a step size spec­i­fi­ca­tion (e.g. 1.8° or 200 steps per rev­o­lu­tion), which applies to full steps. A microstep­ping dri­ver such as the DRV8825 allows high­er res­o­lu­tions by allow­ing inter­me­di­ate step loca­tions, which are achieved by ener­giz­ing the coils with inter­me­di­ate cur­rent lev­els. For instance, dri­ving a motor in quar­ter-step mode will give the 200-step-per-rev­o­lu­tion motor 800 microsteps per rev­o­lu­tion by using four dif­fer­ent cur­rent lev­els.The res­o­lu­tion (step size) selec­tor inputs (MODE0, MODE1, and MODE2) enable selec­tion from the six step res­o­lu­tions accord­ing to the table below. All three selec­tor inputs have inter­nal 100kΩ pull-down resis­tors, so leav­ing these three microstep selec­tion pins dis­con­nect­ed results in full-step mode. For the microstep modes to func­tion cor­rect­ly, the cur­rent lim­it must be set low enough (see below) so that cur­rent lim­it­ing gets engaged. Oth­er­wise, the inter­me­di­ate cur­rent lev­els will not be cor­rect­ly main­tained, and the motor will skip microsteps.MODE0MODE1MODE2Microstep Res­o­lu­tionLowLowLowFull stepHighLowLowHalf stepLowHighLow1/4 stepHighHighLow1/8 stepLowLowHigh1/16 stepHighLowHigh1/32 stepLowHighHigh1/32 stepHighHighHigh1/32 stepControl inputsEach pulse to the STEP input cor­re­sponds to one microstep of the step­per motor in the direc­tion select­ed by the DIR pin. These inputs are both pulled low by default through inter­nal 100kΩ pull-down resis­tors. If you just want rota­tion in a sin­gle direc­tion, you can leave DIR dis­con­nect­ed.The chip has three dif­fer­ent inputs for con­trol­ling its pow­er states: RESET, SLEEP, and ENBL. For details about these pow­er states, see the datasheet. Please note that the dri­ver pulls the SLEEP pin low through an inter­nal 1MΩ pull-down resis­tor, and it pulls the RESET and ENBL pins low through inter­nal 100kΩ pull-down resis­tors. These default RESET and SLEEP states are ones that pre­vent the dri­ver from oper­at­ing; both of these pins must be high to enable the dri­ver (they can be con­nect­ed direct­ly to a log­ic “high” volt­age between 2.2 and 5.25 V, or they can be dynam­i­cal­ly con­trolled via con­nec­tions to dig­i­tal out­puts of an MCU). The default state of the ENBL pin is to enable the dri­ver, so this pin can be left dis­con­nect­ed.The DRV8825 also fea­tures a FAULT out­put that dri­ves low when­ev­er the H‑bridge FETs are dis­abled as the result of over-cur­rent pro­tec­tion or ther­mal shut­down. The car­ri­er board con­nects this pin to the SLEEP pin through a 10k resis­tor that acts as a FAULT pull-up when­ev­er SLEEP is exter­nal­ly held high, so no exter­nal pull-up is nec­es­sary on the FAULT pin. Note that the car­ri­er includes a 1.5k pro­tec­tion resis­tor in series with the FAULT pin that makes it is safe to con­nect this pin direct­ly to a log­ic volt­age sup­ply, as might hap­pen if you use this board in a sys­tem designed for the pin-com­pat­i­ble A4988 car­ri­er. In such a sys­tem, the 10k resis­tor between SLEEP and FAULT would then act as a pull-up for SLEEP, mak­ing the DRV8825 car­ri­er more of a direct replace­ment for the A4988 in such sys­tems (the A4988 has an inter­nal pull-up on its SLEEP pin). To keep faults from pulling down the SLEEP pin, any exter­nal pull-up resis­tor you add to the SLEEP pin input should not exceed 4.7k.Current limitingTo achieve high step rates, the motor sup­ply is typ­i­cal­ly much high­er than would be per­mis­si­ble with­out active cur­rent lim­it­ing. For instance, a typ­i­cal step­per motor might have a max­i­mum cur­rent rat­ing of 1 A with a 5Ω coil resis­tance, which would indi­cate a max­i­mum motor sup­ply of 5 V. Using such a motor with 12 V would allow high­er step rates, but the cur­rent must active­ly be lim­it­ed to under 1 A to pre­vent dam­age to the motor.The DRV8825 sup­ports such active cur­rent lim­it­ing, and the trim­mer poten­tiome­ter on the board can be used to set the cur­rent lim­it. You will typ­i­cal­ly want to set the driver’s cur­rent lim­it to be at or below the cur­rent rat­ing of your step­per motor. One way to set the cur­rent lim­it is to put the dri­ver into full-step mode and to mea­sure the cur­rent run­ning through a sin­gle motor coil with­out clock­ing the STEP input. The mea­sured cur­rent will be 0.7 times the cur­rent lim­it (since both coils are always on and lim­it­ed to approx­i­mate­ly 70% of the cur­rent lim­it set­ting in full-step mode).Anoth­er way to set the cur­rent lim­it is to mea­sure the volt­age on the “ref” pin and to cal­cu­late the result­ing cur­rent lim­it (the cur­rent sense resis­tors are 0.100Ω). The ref pin volt­age is acces­si­ble on a via that is cir­cled on the bot­tom silkscreen of the cir­cuit board. The cur­rent lim­it relates to the ref­er­ence volt­age as fol­lows:Cur­rent Lim­it = VREF × 2So, for exam­ple, if you have a step­per motor rat­ed for 1 A, you can set the cur­rent lim­it to 1 A by set­ting the ref­er­ence volt­age to 0.5 V.Note: The coil cur­rent can be very dif­fer­ent from the pow­er sup­ply cur­rent, so you should not use the cur­rent mea­sured at the pow­er sup­ply to set the cur­rent lim­it. The appro­pri­ate place to put your cur­rent meter is in series with one of your step­per motor coils.Power dissipation considerationsThe DRV8825 dri­ver IC has a max­i­mum cur­rent rat­ing of 2.5 A per coil, but the cur­rent sense resis­tors fur­ther lim­it the max­i­mum cur­rent to 2.2 A, and the actu­al cur­rent you can deliv­er depends on how well you can keep the IC cool. The carrier’s print­ed cir­cuit board is designed to draw heat out of the IC, but to sup­ply more than approx­i­mate­ly 1.5 A per coil, a heat sink or oth­er cool­ing method is required.This prod­uct can get hot enough to burn you long before the chip over­heats. Take care when han­dling this prod­uct and oth­er com­po­nents con­nect­ed to it.Please note that mea­sur­ing the cur­rent draw at the pow­er sup­ply will gen­er­al­ly not pro­vide an accu­rate mea­sure of the coil cur­rent. Since the input volt­age to the dri­ver can be sig­nif­i­cant­ly high­er than the coil volt­age, the mea­sured cur­rent on the pow­er sup­ply can be quite a bit low­er than the coil cur­rent (the dri­ver and coil basi­cal­ly act like a switch­ing step-down pow­er sup­ply). Also, if the sup­ply volt­age is very high com­pared to what the motor needs to achieve the set cur­rent, the duty cycle will be very low, which also leads to sig­nif­i­cant dif­fer­ences between aver­age and RMS cur­rents. Addi­tion­al­ly, please note that the coil cur­rent is a func­tion of the set cur­rent lim­it, but it does not nec­es­sar­i­ly equal the cur­rent lim­it set­ting. The actu­al cur­rent through each coil changes with each microstep. See the DRV8825 datasheet for more infor­ma­tion.Key differences between the DRV8825 and A4988The DRV8825 car­ri­er was designed to be as sim­i­lar to our A4988 step­per motor dri­ver car­ri­ers as pos­si­ble, and it can be used as a drop in replace­ment for the A4988 car­ri­er in many appli­ca­tions because it shares the same size, pinout, and gen­er­al con­trol inter­face. There are a few dif­fer­ences between the two mod­ules that should be not­ed, how­ev­er:The pin used to sup­ply log­ic volt­age to the A4988 is used as the DRV8825’s FAULT out­put, since the DRV8825 does not require a log­ic sup­ply (and the A4988 does not have a fault out­put). Note that it is safe to con­nect the FAULT pin direct­ly to a log­ic sup­ply (there is a 1.5k resis­tor between the IC out­put and the pin to pro­tect it), so the DRV8825 mod­ule can be used in sys­tems designed for the A4988 that route log­ic pow­er to this pin.The SLEEP pin on the DRV8825 is not pulled up by default like it is on the A4988, but the car­ri­er board does con­nect it to the FAULT pin through a 10k resis­tor. There­fore, sys­tems intend­ed for the A4988 that route log­ic pow­er to the FAULT pin will effec­tive­ly have a 10k pull-up on the SLEEP pin. (This 10k resis­tor is not present on the ini­tial (md20a) ver­sion of the DRV8825 car­ri­er.)The cur­rent lim­it poten­tiome­ter is in a dif­fer­ent loca­tion.The rela­tion­ship between the cur­rent lim­it set­ting and the ref­er­ence pin volt­age is dif­fer­ent.The DRV8825 offers 1/32-step microstep­ping; the A4988 only goes down to 1/16-step.The mode selec­tion pin inputs cor­re­spond­ing to 1/16-step on the A4988 result in 1/32-step microstep­ping on the DRV8825. For all oth­er microstep­ping res­o­lu­tions, the step selec­tion table is the same for both the DRV8825 and the A4988.The tim­ing require­ments for min­i­mum pulse dura­tions on the STEP pin are dif­fer­ent for the two dri­vers. With the DRV8825, the high and low STEP puls­es must each be at least 1.9 us; they can be as short as 1 us when using the A4988.The DRV8825 has a high­er max­i­mum sup­ply volt­age than the A4988 (45 V vs 35 V), which means the DRV8825 can be used more safe­ly at high­er volt­ages and is less sus­cep­ti­ble to dam­age from LC volt­age spikes.The DRV8825 can deliv­er more cur­rent than the A4988 with­out any addi­tion­al cool­ing (based on our full-step tests: 1.5 A per coil for the DRV8825 vs 1.2 A per coil for the A4988 Black Edi­tion and 1 A per coil for the orig­i­nal A4988 car­ri­er).The DRV8825 uses a dif­fer­ent nam­ing con­ven­tion for the step­per motor out­puts, but they are func­tion­al­ly the same as the cor­re­spond­ing pins on the A4988 car­ri­er, so the same con­nec­tions to both dri­vers result in the same step­per motor behav­ior. On both boards, the first part of the label iden­ti­fies the coil (so you have coils “A” and “B” on the DRV8825 and coils “1” and “2” on the A4988).For those with col­or-sen­si­tive appli­ca­tions, note that the DRV8825 car­ri­er is pur­ple.In sum­ma­ry, the DRV8825 car­ri­er is sim­i­lar enough to our A4988 car­ri­ers that the min­i­mum con­nec­tion dia­gram for the A4988 is a valid alter­nate way to con­nect the DRV8825 to a micro­con­troller as well:Doc­u­ments Texas Instru­ments DRV8825 step­per motor dri­ver datasheet (1MB pdf)
Motor Drivers

Motor Drivers