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 B-Robot DRV8825 Problem
12-11-2015, 08:46 PM
Post: #14
 KomX Member Posts: 98 Joined: Jun 2015 Reputation: 1
RE: B-Robot DRV8825 Problem
(12-11-2015 06:45 PM)sasa999 Wrote:  From https://www.pololu.com/product/2132

"The DRV8825 supports such active current limiting, and the trimmer potentiometer on the board can be used to set the current limit. 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).
So, for example, if the reference voltage is 0.5 V, the current limit is 1 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 1.5 A, the current limit should be 1.5 A/0.7=2.1 A, which corresponds to a VREF of 2.1 A/2=1.05 V. See the DRV8825 datasheet for more information."
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Looks like this need some real tests for clearance

page 23

IOUT(RMS) is equal to the approximately 0.7x the full-scale output current
setting. The factor of 4 comes from the fact that there are two motor windings, and at any instant two FETs are
conducting winding current for each winding (one high-side and one low-side).

Экий Вы, сэр, неугомонный. Даже худо-бедный перевод гугла дал мне понять, что в первой цитате речь ведут о полношаговом режиме, где как следует из таблицы 2 на стр.14-15 ток действительно не превышает +-71%. В остальных же случаях максимальный ток ограничен 100% (см. первую строку таблицы).
Посему, сто раз проверь, прежде чем советовать человеку с мотором на 1.7А поднимать уровень ограничения тока с учётом этих 70%, ибо новый уровень ограничения тока будет почти на пределе допустимого - 2.43А.
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 Messages In This Thread B-Robot DRV8825 Problem - weekeda - 12-09-2015, 10:49 PM RE: B-Robot DRV8825 Problem - KomX - 12-10-2015, 06:31 AM RE: B-Robot DRV8825 Problem - sasa999 - 12-10-2015, 11:50 AM RE: B-Robot DRV8825 Problem - weekeda - 12-10-2015, 11:51 AM RE: B-Robot DRV8825 Problem - sasa999 - 12-13-2015, 10:33 AM RE: B-Robot DRV8825 Problem - sasa999 - 12-10-2015, 06:45 PM RE: B-Robot DRV8825 Problem - KomX - 12-10-2015, 08:33 PM RE: B-Robot DRV8825 Problem - weekeda - 12-10-2015, 10:45 PM RE: B-Robot DRV8825 Problem - KomX - 12-11-2015, 04:17 AM RE: B-Robot DRV8825 Problem - sasa999 - 12-11-2015, 10:32 AM RE: B-Robot DRV8825 Problem - weekeda - 12-11-2015, 01:45 PM RE: B-Robot DRV8825 Problem - sasa999 - 12-11-2015, 02:16 PM RE: B-Robot DRV8825 Problem - KomX - 12-11-2015, 05:18 PM RE: B-Robot DRV8825 Problem - sasa999 - 12-11-2015, 06:45 PM RE: B-Robot DRV8825 Problem - KomX - 12-11-2015 08:46 PM RE: B-Robot DRV8825 Problem - sasa999 - 12-11-2015, 09:46 PM RE: B-Robot DRV8825 Problem - KomX - 12-12-2015, 07:02 AM RE: B-Robot DRV8825 Problem - sasa999 - 12-12-2015, 09:58 AM

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