Just in case you need galvanically isolated oscilloscope

IMG_20170801_003757.jpgActually it works even from 50Vdc. Just a 12V battery and step-up converter. Only 28W, not much!

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IST3990 Datasheet

IST3990

Some initialisation code:

void init()
{
//RES=0;
//delay(2);
//RES=1;
delay(20);
write_com(0x3A);        //0 0 1 1 1 0 1 OSCOFF
write_com(0x2F);        //0 0 1 0 1 1 VC VF
write_com(0x35);        //0 0 1 1 0 BS2 BS1 BS0    30=1/7, 31=1/8, 32=1/9, 33=1/10, 34=1/11, 35=1/12, 36=1/13, 37=1/14
write_com(0x90);        //1 0 0 1 0 0 0 0
write_com(0x80);        //DUTY7-0
write_com(0xB1);        //DUTY7-0
write_com(0x58);        //3C=0.7 V0=12V     5DH=14V
write_com(0xB2);        //FR:3B     013C=74Hz
write_com(0x3C);        //LN7-0
write_com(0x01);        //LN15-8
write_com(0x6C);        //0 1 1 0 SHL ADC EON REV
write_com(0x44);        //GRAY CONTROL 44H=MONO  45H=4GRAY
write_com(0x88);        //TEST COMMAND SET
write_com(0x88);        //TEST COMMAND SET
write_com(0x88);        //TEST COMMAND SET
write_com(0x88);        //TEST COMMAND SET
write_com(0x8A);        //1 0 0 0 1 BT2-0  BT2-0 000-100 EQU X4-X8 000=x4 001=x5 010=x6 011=x7 100=x8
write_com(0x60);        //0 1 1 0 0 SCAN_MOD1 SCAN_MOD0 MAP_MODE
write_com(0x41);        //TEST COMMAND SET
write_com(0x19);        //1 0 0 0 1 BT2-0  BT2-0 000-100 EQU X4-X8 000=x4 001=x5 010=x6 011=x7 100=x8
write_com(0x2f);
write_com(0xE3);

/*write_com(0x74);
write_com(0x00);        //
write_com(0x7F);        //
write_com(0x75);        //SET WINDOWS AX
write_com(0x02);        //
write_com(0x1F);        //
write_com(0xC0);        //SET WINDOWS AY
write_com(0x02);        //
write_com(0x01);        //
write_com(0x00);        /*/

delay(50);
write_com(0x3D);        //0 0 1 1 1 1 0 DON    set Display ON
delay(50);
}

BLDC Back EMF integration understanding #1

Most of documents about this article show two basic formula –
For PWM off time – Vphase = 3/2*e
For PWM on time – Vphase = 3/2*e + Vdc/2
And show us beautiful voltage waveforms with PWMed BEMF, where ON and OFF time parallel. But i have another situation with mine 8kW hub-motor. Look at this:
symetrical
Typical examle, where off-time BEMF differs from on-time on Vdc/2. Here’s mine:non-equal
Second PWM cycle inverted. Green area- affected by diode, integration starts in red area, after zero crossing. Closer view:
DS1Z_QuickPrint9DS1Z_QuickPrint10
At the beginning of the cycle is seen resonant oscillations, for my motor they lasts about 10uS, ADC samples in center of ON time and OFF time, what give us clear data, without interference.

What is source of this mis-alignment? For proper BEMF integration i should take phase voltage, subtract neutral point, and integrate the resulting value. For off-time it is right, if we take neutral point as zero, coz other two phases on the ground, resultant step-switch very accurate with installed hall sensors. But if i take raw value from on-time, subtract Vdc/2, voltage is incorrect, step-switch comes too early. This means neutral point moves with BEMF, actually it is always moves, coz of third harmonic, but this is seen only when two other phases is powered.

LiFePO4. Безопасность.

В предыдущем посте я оговаривал причины выбора LiFePO4 аккумулятора, и одним из аргументов было то что его можно проткнуть гвоздем, и ничего страшного не произойдет. Вот хороший видос на эту тему:

Кромсаем LiFePO4 баттарейку

UPD:

А вот видео от отечественного эксперементатора 🙂 если кажется что первое – фейк.