Modifications

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== Où acheter ==

== Les sources d'alimentation ==

* {{pl|349|Controleur moteur pas-à-pas A4988}}

 

La tension d'alimentation moteur est comprise entre 8 et 35 V qui doit être connecté entre les broches VMOT et GND. Cette alimentation devrait être accompagnée d'une capacité de découplage proche de la carte, et devrait être capable de délivrer le courant attendu (des pointes jusqu'à 4 A pour l'alimentation moteur.

[[Fichier:A4988-decouplage.jpg]]

The driver requires a logic supply voltage (3 – 5.5 V) to be connected across the VDD and GND pins and a motor supply voltage (8 – 35 V) to be connected across VMOT and GND. These supplies should have appropriate decoupling capacitors close to the board, and they should be capable of delivering the expected currents (peaks up to 4 A for the motor supply).

{{ambox-stop|text=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 35 V maximum voltage rating for the A4988 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.}}

{{ambox-stop|text=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 35 V maximum voltage rating for the A4988 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.}}

== Branchement moteur ==

== Branchement moteur ==

{{ambox-stop|text=Warning: 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.)}}

{{ambox-stop|text=Connecter ou déconnecter les moteurs pas-à-pas pendant que le pilote est sous tension peut le détruire.}}

 

D'une façon générale, changer le câblage en cours de fonctionnement sera la source de problèmes.

== Limiter le courant ==

== Limiter le courant ==

So, for example, if the reference voltage is 0.3 V, the current limit is 0.75 A. As mentioned above, in full step mode, the current through the coils is limited to 70% of the current limit, so to get a full-step coil current of 1 A, the current limit should be 1 A/0.7=1.4 A, which corresponds to a VREF of 1.4 A/2.5=0.56 V. See the A4988 datasheet for more information.

So, for example, if the reference voltage is 0.3 V, the current limit is 0.75 A. As mentioned above, in full step mode, the current through the coils is limited to 70% of the current limit, so to get a full-step coil current of 1 A, the current limit should be 1 A/0.7=1.4 A, which corresponds to a VREF of 1.4 A/2.5=0.56 V. See the A4988 datasheet for more information.

{{ambox-stop|text=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.}}

{{ambox|text=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.}}

   

   

== Dissipation de chaleur ==

== Dissipation de chaleur ==

The A4988 driver IC has a maximum current rating of 2 A per coil, but 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 A per coil, a heat sink or other cooling method is required.

The A4988 driver IC has a maximum current rating of 2 A per coil, but 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 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.}}

{{ambox|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.}}

'''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.

'''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.