Recent content by ShawnS

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    Phase Shift Oscillator Puzzle

    You are correct - the square wave is the desired output. Waveshape is not a concern here since the output frequency is what is needed. I will experiment with larger resistor values and smaller caps and see what happens. The 1k ohm resistors was selected to match the RTD's on hand nominal...
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    Phase Shift Oscillator Puzzle

    Good idea! Please see attached. The HCU04 shows no sign of abnormal heating. All unused gate inputs were pulled low. Current to IC is around 8 mA from 3.3 V.
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    Phase Shift Oscillator Puzzle

    Update - unfortunately the circuit as drawn using "RNEW" would not oscillate for me, so I turned back to using the HCU04 and a low pass phase shift network which seems much more stable. I am somewhat surprised that the frequency is affected so much by the supply voltage though since the phase...
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    Phase Shift Oscillator Puzzle

    Thanks AK. I have not ruled that out, but the low pass type puts the output in the frequency range I prefer ( < 10 kHz).
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    Phase Shift Oscillator Puzzle

    Whonoes - thanks for the reply. I would rather if possible keep to a phase shift network to define the frequency. As I understand the "relaxation" kind will be somewhat dependent on trigger thresholds, vary a lot over temperature, and not as reproducible.
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    Phase Shift Oscillator Puzzle

    Audioguru - thank you for the info! I have some of those on hand and will be trying them soon. Stand by for the results.....
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    Phase Shift Oscillator Puzzle

    Hi Cannonball thanks for your reply. Please take note that I was able to get this to work with a transistor (lowly 3904 in fact). It's getting it to work with the inverter gate is the issue.
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    Phase Shift Oscillator Puzzle

    Hello all - my first post here! I've been developing an oscillator circuit in which I want to place an RTD (1 kohm nominal) to develop an output frequency that is dependent on the resistance. The op amp RC oscillator does the trick, but for various reasons (due to environment) op amps are not...
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