MrHeckles Posted November 11, 2005 Report Share Posted November 11, 2005 This is my current circuit as it standsWhat I am trying to get is the LED to turn on when the voltage across the sense resistor (0.32 ohm) gets above 0.2vI have set up the LM311 comparator as shown. However it doesnt seem to work as I thought it would. The LED turns on as soon as there is ANY voltage across the sense resistor (ie when the mosfet starts switching on).I have also tried it with the inputs round the other way. That didnt work as I wanted either.Please could someone let me know where my schematic is incorrect.Thanks Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 11, 2005 Report Share Posted November 11, 2005 The datasheet shows that there are voltage spikes across the sense resistor. It needs a filter like this, but it will cause a small delay. Quote Link to comment Share on other sites More sharing options...
MrHeckles Posted November 13, 2005 Author Report Share Posted November 13, 2005 I put the filter in and after fiddling with the values of things got it all working.Many thanks audioguru Quote Link to comment Share on other sites More sharing options...
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