Prefix: New here and to electronics.
I'm working on a project that will be run with a raspeberry pi. The area that I'm a bit confused on is where I am interfacing a freescale mpx5010 pressure sensor to an ADC MCP3008.
The mpx5010 will be driven with 5V from a regulator board, the MCP3008 with 3.3V from the Rpi.
Although the output of the mpx5010 sensor can be in the 0-4.7V range, in this application, under normal use, it will produce no more than 2.5V. This should provide me with 2.5V on the 3.3Vref scale on the ADC, so thats enough resolution for what I'm after.
Now my concern is protecting those ADC inputs from the potential max voltage output of the sensor, just in case someone does something unexpected.
I was considering a 3.3Vz zener diode from the sensor output to ground, which should clamp things to ~3.5V max (I think) on the input which is fine as the MCP3008 datasheet says Vdd +0.6, so anything < 3.9V is safe (thats another I think).
In looking at zener diode clipping circuits there is always a resistor in series with the input signal, and I have no idea how to size that, or if its even needed?
I also read about those types of clipping circuits altering the below clip signal / value as well. I'm not sure that is a concern given the max range I'm interested in being 2.5, so as long as the 0-2.5V output of the sensor is not altered and I clip anything above 3.3V (3.9V max) it should be fine.
I've attached a quick pic of the specifics, input on how this should be done and how to size the components are greatly appreciated!
I'm working on a project that will be run with a raspeberry pi. The area that I'm a bit confused on is where I am interfacing a freescale mpx5010 pressure sensor to an ADC MCP3008.
The mpx5010 will be driven with 5V from a regulator board, the MCP3008 with 3.3V from the Rpi.
Although the output of the mpx5010 sensor can be in the 0-4.7V range, in this application, under normal use, it will produce no more than 2.5V. This should provide me with 2.5V on the 3.3Vref scale on the ADC, so thats enough resolution for what I'm after.
Now my concern is protecting those ADC inputs from the potential max voltage output of the sensor, just in case someone does something unexpected.
I was considering a 3.3Vz zener diode from the sensor output to ground, which should clamp things to ~3.5V max (I think) on the input which is fine as the MCP3008 datasheet says Vdd +0.6, so anything < 3.9V is safe (thats another I think).
In looking at zener diode clipping circuits there is always a resistor in series with the input signal, and I have no idea how to size that, or if its even needed?
I also read about those types of clipping circuits altering the below clip signal / value as well. I'm not sure that is a concern given the max range I'm interested in being 2.5, so as long as the 0-2.5V output of the sensor is not altered and I clip anything above 3.3V (3.9V max) it should be fine.
I've attached a quick pic of the specifics, input on how this should be done and how to size the components are greatly appreciated!
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