niveK Posted July 10, 2009 Report Share Posted July 10, 2009 Good day. I’ve built the following circuit in hopes that it will detect when Vin exceeds 4 Volts for more than 2 seconds.Built it last night but no such luck. Pin 3 (non inverting input) is held low at around 0.5 volts and the output therefore will not go high. Disconnecting R2 fixes the problem and circuit operates but there is slight oscillation due to no hysteresis. Any suggestions on how I can add hysteresis to this circuit? Thank you. Quote Link to comment Share on other sites More sharing options...
blueroomelectronics Posted July 10, 2009 Report Share Posted July 10, 2009 Why not use a comparator & a timer like the 555? Quote Link to comment Share on other sites More sharing options...
niveK Posted July 10, 2009 Author Report Share Posted July 10, 2009 Thank you for your reply. I Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted July 21, 2009 Report Share Posted July 21, 2009 You might try using negative feedback instead of positive feedback if you don't need that high of gain. Opamps can latch up and the switch point voltages can be hard to control. Even at a low gain, getting the bias you want is sometimes difficult. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.