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Ligne 49 : − − == Où Acheter == − * {{pl|454|Le DRV8825 est disponible chez MCHobby}} − Vous trouverez également les produits suivants: − * {{pl|10|Arduino Uno}} − * {{pl|34|Fils de prototypage}} − * {{pl|53|Breadboard}} − * {{pl|420|FabScan/StepStick shield}} − A voir aussi − * {{pl|349|Pilote de moteur pas-à-pas A4988}} Ligne 87 :
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aucun résumé de modification
* '''Fault:''' Logique inversée. Branchez une tension entre 2.5 et 5.25v, celle qui alimente votre microcontrôleur.
* '''Fault:''' Logique inversée. Branchez une tension entre 2.5 et 5.25v, celle qui alimente votre microcontrôleur.
* '''GND:''' sous FAULT. Masse commune avec votre microcontrôleur.
* '''GND:''' sous FAULT. Masse commune avec votre microcontrôleur.
== Connecter l'Alimentation ==
== Connecter l'Alimentation ==
[[Fichier:STEPSTK-DRV8825-nSleep.jpg]]<br /><small>Schematic of nSLEEP and nFAULT pins on DRV8824/DRV8825/DRV8834 carriers.</small>
[[Fichier:STEPSTK-DRV8825-nSleep.jpg]]<br /><small>Schematic of nSLEEP and nFAULT pins on DRV8824/DRV8825/DRV8834 carriers.</small>
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.
== Limitation de courant ==
To 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 × 2
So, 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.
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.
{{ambox-stop|text=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.}}
== Considérer la dissipation de chaleur ==
The 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.
{{ambox-stop|text=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.}}
{{underline|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.}}
== Diagramme schématique ==
[[Fichier:DRV8825-schema.jpg]]
The current sense resistors (R2 and R3) on the DRV8825 carrier are 0.100 Ω. This schematic is also available as a [http://www.pololu.com/file/download/drv8824-drv8825-stepper-motor-driver-carrier-schematic-diagram.pdf?file_id=0J603 downloadable pdf] (196k pdf).
== DRV8825 et A4988 - les différences clés ==
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== Où Acheter ==
* {{pl|454|Le DRV8825 est disponible chez MCHobby}}
Vous trouverez également les produits suivants:
* {{pl|10|Arduino Uno}}
* {{pl|34|Fils de prototypage}}
* {{pl|53|Breadboard}}
* {{pl|420|FabScan/StepStick shield}}
A voir aussi
* {{pl|349|Pilote de moteur pas-à-pas A4988}}
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