Greetings,
I am trying to utilize an LM2907 Tachometer (the 14 pin package) to convert the frequency of the rotation of an RC car wheel into a voltage, which will eventually be used for feedback reference for speed control using a PI controller. Anyways, an IR-encoder reads the interior of the wheel that has reflective and non-reflective tape sectioned into 8 sections, like a pizza. After reading the datasheet for the LM2907, I am having some confusion on the purpose of pin 11 on the 14-pin package. It is listed as TACH-, and is internally grounded on the 8-pin package. The description of the pin on the datasheet is the negative terminal of the input signal to the non-inverting terminal of the internal schmitt trigger. The input signal would be a 0-6V square wave (I have the encoder feed into a previous schmitt trigger to help clean up the signal and give a true high-low waveform). Would the 0V that could be fed into the input be fighting with this pin 11 TACH- as to which is technically the lower potential? Or would I need say a voltage divider to be attached to that pin to give it a slight bias?
I am trying to utilize an LM2907 Tachometer (the 14 pin package) to convert the frequency of the rotation of an RC car wheel into a voltage, which will eventually be used for feedback reference for speed control using a PI controller. Anyways, an IR-encoder reads the interior of the wheel that has reflective and non-reflective tape sectioned into 8 sections, like a pizza. After reading the datasheet for the LM2907, I am having some confusion on the purpose of pin 11 on the 14-pin package. It is listed as TACH-, and is internally grounded on the 8-pin package. The description of the pin on the datasheet is the negative terminal of the input signal to the non-inverting terminal of the internal schmitt trigger. The input signal would be a 0-6V square wave (I have the encoder feed into a previous schmitt trigger to help clean up the signal and give a true high-low waveform). Would the 0V that could be fed into the input be fighting with this pin 11 TACH- as to which is technically the lower potential? Or would I need say a voltage divider to be attached to that pin to give it a slight bias?
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