Hey all,
I have spot welder project in mind. In this project i am hoping to add a feature to measure the weld current on every weld. The resistance of the weld cable is only measured once during assembly. Using that and the weld voltage, measured at the Positive (+) electrode together can calculate the weld current using ohm's Law.
Here is what i hope to accomplish or could be wrong completely. Once the electrodes are shorted the base of Q1(iSet) is set high by the microcontroller. This would set a constant current of 1A by the op-amp via the feedback pin on U1. A voltage drop at the cable would be read at pin Vw which would be the total resistance from the positive electrode to gnd. The MOSFETs have a 9mOhm Rds(ON) resistance so minus it from the total resistance would give the cable resistance. So during a weld Vw would read the voltage, with ohms law calculating current would be possible.
The voltage from the supercap is 8.1v, R1 is set 8Ohms to set the current at 1A.
Am i correct with this assumption ?
I have spot welder project in mind. In this project i am hoping to add a feature to measure the weld current on every weld. The resistance of the weld cable is only measured once during assembly. Using that and the weld voltage, measured at the Positive (+) electrode together can calculate the weld current using ohm's Law.
Here is what i hope to accomplish or could be wrong completely. Once the electrodes are shorted the base of Q1(iSet) is set high by the microcontroller. This would set a constant current of 1A by the op-amp via the feedback pin on U1. A voltage drop at the cable would be read at pin Vw which would be the total resistance from the positive electrode to gnd. The MOSFETs have a 9mOhm Rds(ON) resistance so minus it from the total resistance would give the cable resistance. So during a weld Vw would read the voltage, with ohms law calculating current would be possible.
The voltage from the supercap is 8.1v, R1 is set 8Ohms to set the current at 1A.
Am i correct with this assumption ?
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