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I am designing a circuit for driving the stepper motor, the link attached (https://www.alibaba.com/product-detail/3v-12mm-2-phase-micro-dc_60641420857.html?spm=a2700.7724838.2017115.17.149a279bsYy1CA&s=p) using 2xAA (2.4V) NiMH 800mAh batteries. Also, I am using a boost converter U1V10F5 (0.5V-5.5V)to step up from 2.4V to 5V to power up the motor as well as the driver (DRV8834). I've found that the motor that runs at 2.7V consumes approximately 70mA. The question is if I am using normal 2xAA(3V) battery or bench power supply (set it to 2.7V) the circuit is working fine and the motor is running. Whenever I set the voltage to 2.6V or 2.4V on the bench power supply or connect the 2XAA rechargeable battery my motor stops working.

Is that the rechargeable battery not having enough capacity? or the step up booster is not able to supply enough current to drive the motor at 2.4V? Please let me know why the motor is not running at 2.4V and runs at 2.7V. I have attached the rough schematic. I am using two PSU for the microcontroller(5V@3A) and the motor(2xAA(2.4V)) indicated in dotted lines in the schematic. Your guide is much appreciated.

Thanks in advance.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ aren't there any capacitors on the output of your U1V10F5? \$\endgroup\$ – BeB00 Oct 26 '17 at 14:36
  • \$\begingroup\$ oh I see, they're already part of the package \$\endgroup\$ – BeB00 Oct 26 '17 at 14:37
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    \$\begingroup\$ I suspect that the series resistance of the loop AA-batteries to Boost converter and back (ground connection) has too much series resistance. How is this build up, on a breadboard? With connectors ? The series resistance that I mention must be really low otherwise the boost converter cannot extract enough energy from the batteries. The current into the boostconverter is about 150 mA on average but it will be pulsed. Those pulses can be up to 1 A. If too much voltage is dropped across connections then the inductor (in the converter) cannot charge properly and output current is limited. \$\endgroup\$ – Bimpelrekkie Oct 26 '17 at 14:38
  • \$\begingroup\$ @Bimpelrekkie Thanks for your help. I've built up in Vero board using the connector and bridged them using solder. Will that make any difference? \$\endgroup\$ – Dhinesh Oct 26 '17 at 14:56
  • \$\begingroup\$ @BeB00 Thanks for your help. Yes, it is already built-in. \$\endgroup\$ – Dhinesh Oct 26 '17 at 14:56

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