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davepusey said:I have a 0.25Hz square wave (50% duty cycle) and i need to make it lag by 90 degrees. How do i do this? Please help.
Nigel Goodwin said:Please tell us what you are trying to do, and why?. It's pointless offering suggestions when we don't know what it's supposed to be doing, a generic question can have too many answers - many of which may be totally irrelevent to your question.
Styx said:If you want the square waveform lag the triangle waveform the easiest way is to pass the teh squarewave through a lowpass RC filter (best bet is to use a veriable resistor for this bit then fix the value later)
Then this new "curvy" waveform pass through one gate from a 74HC14 HEX Schmitt trigger inverter (and then another one of the inverters otherwise you have an extra 180deg shift to deal with).
The 74HC14 schmitt trigger action will regenerate a square wave from teh curvy one, but due to the (internal) hysteresis it will be delayed. How much it is delayed depends on the time constant of the RC
I us this cct all the time to make intelocks between PWM for quick motor-drives
davepusey said:I have a 0.25Hz square wave (50% duty cycle) and i need to make it lag by 90 degrees. How do i do this? Please help.
spuffock said:Nigel has the easiest option, but I have to argue that the switching point should be decided by a change of direction of the a/d reading rather than a fixed point. The accuracy will be a bit better than half a degree and the settling time will be within half a cycle. An alternative using a phase locked loop can be more accurate, but will take a long time to settle(minutes) after any disturbance or small change of frequency.