This is my first time in this forum. I'm new to the electrical engineering and need to develop a project for school. This device / project needs to measures pressures remotely in a vehicle. I'm confused on how it should be assembled.
It needs to have the following conditions:
1.) Have a microcontroller with as little power consumption as possible. I'm leaning toward a Heltec Automation ESP32 Wi-fi. Cheap and low powered. Feel free to suggest any other options.
2.) Connect an 4-20 ma pressure sensor.
3.) Power the whole thing using a 3.7 Volt battery pack (Picture Displays 3.4 Volt. This is a typo. Sorry)
4.) Set the sensor to sleep for several minutes to save battery life. I will have questions about the programming a little later.
As mentioned above, I'm confused on the diagram of how I should assemble it. Thanks ahead of time. I know I will need a resistor. But what kind and value? Is it as simple as V=IR? I'm going to wire with a bread board. Please look at the attachment.
I've not done any extensive searching however I doubt you will find a 4 - 20 ma sensor that can be powered by 3.4V . Usually 4 - 20 ma sensors need > 12V to operate.
You might find a pressure sensor that operates at 3.3V (same as 3.4).
My apologies, I thought most pressure transducers were the same. I purchased the following off of Amazon (Pressure Transducer, Water Pressure Transducer 4-20mA Output G1/4" Silicon Pressure Transmitter Transducer for Water Gas Oil(0-1MPA)).
I'm not sure what voltage is required to power this transducer. I thought with it being 4-20 ma, one could use any type of Transducer. I guess I'm wrong?
Most 4-20mA transducer/sensors require a 24Vdc supply, an industry standard.
But you may need to experiment with as low as 12V to see if it will perform.
Your circuit will work, just need to check supply.
That is the standard way of converting the 4-20mA to a voltage for ADC measurement.
I won't be able to use the power voltage from the vehicle. It has to be stand alone. I was thinking more of a 3.7 Li-Po Battery.
I'm not sure what voltage is required to power this transducer. I thought with it being 4-20 ma, one could use any type of Transducer. I guess I'm wrong?
Thank you for all your help. So, would a 4-20 ma pressure transducer be the incorrect way to go? I wonder if the Professor did this on purpose. He is tricky guy!
It seems maybe 0.5-2.5 Voltage maybe the way to go? I know the 4-20 ma is very accurate, but considering the wire being less than 1.0 ft. long. I imagine we won't lose much accuracy.
If I use a 0.5-2.5 Voltage Transducer, can I still use the Analog or ADC on the board?
Thanks again for the help. I spoke with my professor and come to find out, he tricked us on purpose. I spoke with him about the voltages. He knows the 0.5-2.5 voltage transducer is expensive and the 4-20 am transducer needs a bigger battery.
My plan is to use the battery below (3.7V 1000mah) since the board is only good for 3.3 Volts. One thing I didn't think about is how to power the board and transducer at the same time.
Questions:
Could the pressure transducer (0.5V~4.5V) be powered through the ESP 32 board or does the battery need to be separate from the board and the transducer to avoid noise?
Could I still use a pressure transducer with a voltage of 0.5V~4.5V? I know the max voltage would be 3.3V or 3.7V depending on how to wire the battery to power the board and the transducer. The psi would be incorrect due to it not having 4.5 volts.
If the project spec says you need to use a 4-20mA sensor WHY are you looking at other types?
That isnt why a 4-20mA range is used. Its to avoid voltage losses in connecting wires. You simply convert I to V at your measuring device with a fixed ( small) resisitor.
So a 50 ohm r would give you voltages between 200mV & 1.0V, suitable for your ADC.
