Hi, so I want to do a current detection on mains voltage. To tigger an event. The trigger will feed into a micro-processor to measure the time it took to reach a predefined current level. Therefore, the trigger can be any sort of suitable digital signal.
1) The voltage in line with EU regulations can vary between 216 to 253 Volts.
2) As soon as the current flow reaches 100mA I want to trigger the microprocessor.
a) The 100mA does not have to be an accurate 100mA.
b) It can be in the range say 90mA to 110mA
c) The requirement is that it must be a consistent repeatable level that triggers the event.
d) It can trigger for example on 105mA, the requirement is that no matter what the voltage the trigger will occur at the same 105mA consistently.
3) The trigger processing time must also be consistent.
a) Again, as per the level detection, not an absolute measurement just a consistent repeatable time to generate a trigger.
b) For clarification, the time from the source reaching the example 105mA, to the generation of the interrupt must be consistently the same.
c) Or at least within a few micro-Secs (+/- 5µS).
I did originally think of using a simple resistor network drop and triggering the current with an OP Amp across the current measuring resistor. But this trigger current would vary with the changing voltage.
Next, I considered using A to D to measure and compensate. But the repeatability of conversion times is not accurate enough. Sampling times would be the min and max variations.
I am going around in circles trying to get the consistently repeatable time and level. I welcome any new ideas and thoughts.
1) The voltage in line with EU regulations can vary between 216 to 253 Volts.
2) As soon as the current flow reaches 100mA I want to trigger the microprocessor.
a) The 100mA does not have to be an accurate 100mA.
b) It can be in the range say 90mA to 110mA
c) The requirement is that it must be a consistent repeatable level that triggers the event.
d) It can trigger for example on 105mA, the requirement is that no matter what the voltage the trigger will occur at the same 105mA consistently.
3) The trigger processing time must also be consistent.
a) Again, as per the level detection, not an absolute measurement just a consistent repeatable time to generate a trigger.
b) For clarification, the time from the source reaching the example 105mA, to the generation of the interrupt must be consistently the same.
c) Or at least within a few micro-Secs (+/- 5µS).
I did originally think of using a simple resistor network drop and triggering the current with an OP Amp across the current measuring resistor. But this trigger current would vary with the changing voltage.
Next, I considered using A to D to measure and compensate. But the repeatability of conversion times is not accurate enough. Sampling times would be the min and max variations.
I am going around in circles trying to get the consistently repeatable time and level. I welcome any new ideas and thoughts.