I ordered a TI LNA for my water/air pressure sensor but it is appealing to use the built-in amp. If your pressure sensor has a Wheatstone bridge configuration and is insensitive, consider using the HX711 "24-Bit Analog-to-Digital Converter (ADC) for Weigh Scales". It's available as a chip, or as a ...

Hi Herbie, I am pleased that you are now seeing the temperature displayed on your web page. The function server.send_P is for when you have pointers to 'char' arrays. I don't have much expertise in this area, but I see the constructor for your server object can also take two parameters: an IP addres...

I'm not familiar with the server library and have not looked at all your code in detail, but I think you need to use server.send, not server.send_P. Does that work?

As index_html needs to be modifiable, it should not be declared using the 'const' keyword. It's therefore also inappropriate to use PROGMEM. You could even avoid using index_html at all: server.send_P(200, "text/html", before+temperature_string+after); Were you seeing "This should show the temperatu...

Within index_html[] you need to replace the text "This should show the termperature" with what's in the temperature_string variable before sending the HTML. (I assume you are seeing that text on your computer's browser.) I suggest you split index_html[] before and after "This should show the tempera...

An ADC set to maximum attenuation of 11dB will only measure up to about 3.1V on a 3.3V supply, and even then with lots of non-linearity. I therefore doubt it's possible to use an ADC to measure Vdd via internal connection. The suggestion in a previous post to use a voltage divider makes sense. That ...

Non-linearity is bad with 11dB attenuation and input voltages greater than about 2.6V, as shown by the graph in the original post of this thread. Factory "two point" calibration will not remove that non-linearity. From my measurements, graphs with 6dB and 0dB attenuation appear to have good linearit...

The ESP32 datasheet says that a digital input voltage should be between -0.3V and VDD+0.3V. A graph on the BAT760-7 datasheet indicates that the diode at 0°C will drop 0.3V at about 25mA. Assuming the input voltage range also applies to ADC inputs and ignoring tolerances, 25mA through 150K would req...

. . . would I calculate the voltage divider as 6.8v input? As you wish to measure up to 18V, you don't want the zener to be conducting when you have 18V input. A datasheet I'm looking at for a particular 6.8V zener gives a tolerance of 6.4V to 7.2V at 5mA. A graph on the datasheet clearly shows the...

You are right to be concerned about protecting the ADC input. It is said that there can be substantial voltage spikes on car battery voltages but I have not seen any information about what voltages can be expected. Don't forget to also protect the power supply to your ESP32. The voltage-current char...