2
\$\begingroup\$

I have seen a schematic for a line following robot, but there is something that I can't understand and is shown in the figure below, what is the purpose of the Op Amp circuit? I know that BREAK input in H-Bridge is independent on other pin. Could some one explain what this circuit does?

enter image description here

\$\endgroup\$
1
  • \$\begingroup\$ note that the BREAK G is refer to BREAK D \$\endgroup\$ – Learner Dec 28 '13 at 18:04
2
\$\begingroup\$

The device that looks like an opamp is a comparator, it compares the REF_I_MAX input with ISENSE_G input. The output is low unless the sense level becomes higher than the reference voltage in which case the BRAKE_G output becomes high.

Seems to be a brake mechanism that is activated when the current of the motor exceeds the reference level (for whatever reason).

\$\endgroup\$
4
  • 1
    \$\begingroup\$ does the current of DC motor growing with time ? i think that the amount of current remain constant \$\endgroup\$ – Learner Dec 29 '13 at 6:26
  • \$\begingroup\$ @Hassan The motor uses more current at startup and as it accelerates the current gradually drops. The motor current can also increase where there is a load that resists the spindle rotation and tries to slow the motor down (like an obstacle in the case of the robot). \$\endgroup\$ – alexan_e Dec 29 '13 at 10:16
  • \$\begingroup\$ That does not make sense at all. An op-amp has very high input impedance - it cannot take current as an input. For a transresistance configuration like this, the current can't be driven directly into the input terminals. Is this perhaps more of a block diagram? \$\endgroup\$ – sherrellbc Jun 28 '14 at 14:20
  • \$\begingroup\$ @sherrellbc . . it would seem that ISENSE_G could be a current sensor with a voltage output. \$\endgroup\$ – Marla Jun 28 '14 at 14:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.