Reading pressures off a Edwards Lifescience Pressure Transducer

Using Arduino Sensors
1

Hello,

I am fairly new to arduino in general. I am undertaking a project in which a pressure must be recorded from a pressure transducer and stored on a server. I am unsure how I will read data from this specific type of pressure transducer.

The pressure transducer I have to read pressure data from is a Edwards Lifescience PXVK0996 “TruWave pressure monitoring set”.

Some details on the pressure transducer: 07460691955431 GUDID Code | PXVK0996 Model | Edwards Lifesciences LLC | Global Unique Device Identification Database Directory | Medical Coding Library | www.HIPAASpace.com © 2023

Some details on the general schematics of these transducers:
https://www.edwards.com/eu/products/pressuremonitoring/Pages/truwavekits.aspx

I am also in possession of a converter for the plug that goes to VGA.

If anyone can offer any guidance on how I can read data from the pressure transducer, please let me know. I am not too good with the hardware side of these projects.

2

I couldn’t find anything in the dats sheets that identifies a signal output .
This seems an odd device to use , unless it is a medical application - for which the Arduino is not suitable

3

hammy:
I couldn’t find anything in the dats sheets that identifies a signal output .
This seems an odd device to use , unless it is a medical application - for which the Arduino is not suitable

It is for a medical device. The VGA is a 9 pin. I found a schematic for the 9 pin: RS232 9 Pin Pinout | 9 Pin RS232 Pinout Explained

Can anyone let me know how I would wire this to a breadboard in order to read the data signal into the serial monitor on an arduino?

4

tylarthefarmer:
It is for a medical device. The VGA is a 9 pin. I found a schematic for the 9 pin: https://www.stratusengineering.com/rs232-9-pin-pinout/

Can anyone let me know how I would wire this to a breadboard in order to read the data signal into the serial monitor on an arduino?

That is fine for a general spec of the possible standard 9-pin connections, but may not be how Edwards has implemented it. We need to know the actual pin-out of the Edwards device and the data and communications protocol used by Edwards before much help can be offered.

Paul

5

Paul_KD7HB:
That is fine for a general spec of the possible standard 9-pin connections, but may not be how Edwards has implemented it. We need to know the actual pin-out of the Edwards device and the data and communications protocol used by Edwards before much help can be offered.

Paul

Thank you for the response. I suppose I have to contact Edwards directly and see if they have some schematic?

6

The electrical connections can eventually be figured out with a volt meter. What you need to document is the baud rate, the data format, ie. data bits, parity, check byte(s) for each message. What you need to send to the device, if anything.

Paul

7

Hi,
You will need to look up about powering the device you use to monitor the pressure transducer as it is a medical device that will be connected to a human being.

As you will be aware there are some pretty strict regs on isolation and ground resistance.

Just looking at the specs and other google searches, the comms may be a proprietary system, but you can only ask.

Tom... :slight_smile:

8

Paul_KD7HB:
The electrical connections can eventually be figured out with a volt meter. What you need to document is the baud rate, the data format, ie. data bits, parity, check byte(s) for each message. What you need to send to the device, if anything.

Paul

The only thing I need from the pressure transducer is the pressure it is reading. If you're asking what I need to send to the pressure transducer, I believe it only needs power.

Could you help me get started on how I would figure out each electrical connection using a volt meter? Or refer me to a resource that could assist me with that?

Thank you so much.

9

TomGeorge:
Hi,
You will need to look up about powering the device you use to monitor the pressure transducer as it is a medical device that will be connected to a human being.

As you will be aware there are some pretty strict regs on isolation and ground resistance.

Just looking at the specs and other google searches, the comms may be a proprietary system, but you can only ask.

Tom... :slight_smile:

As far as I know the device should conform to those power regulations. Thank you for the heads up.

10

tylarthefarmer:
The only thing I need from the pressure transducer is the pressure it is reading. If you're asking what I need to send to the pressure transducer, I believe it only needs power.

Could you help me get started on how I would figure out each electrical connection using a volt meter? Or refer me to a resource that could assist me with that?

Thank you so much.

Sorry, In all things electronics, just believing something doesn't make it so. When you get the communications protocol and the data formats and the actual pins being used by the device, then it will be time to talk about hooking it up.

At this point we don't even know if it using RS-232, RS-485 or RS-242 connection.

Paul

11

Hello,

I am having trouble reading data from an MCP3424 chip, specifically the one from this website:

I have a pressure transducer that connects to the MCP3424 chip. The chip is then connected to a NodeMCU 1.0. Schematics are attached.

I am new to this kind of stuff, and I do not know what code is needed on the NodeMCU to read the data coming in from the pressure transducer via the MCP3424 chip. My code currently contains code from here:

My code, attached, is set to upload the error message I am getting from the MCP3424 to a spreadsheet so I can read the error. The error I get is "i2c". I am not sure what that means. I have tried contacting the author of the code but I have not received a response in a week. I simply want to read the pressure I am getting from the pressure transducer from the MCP3424 chip.

Some useful information about the MCP3424 chip can be found here:

If anyone can provide any guidance, code, or helpful advice, that would be extremely appreciated.

pcb_board_nodemcu_final_v2.pdf (29 KB)

code.ino (3.97 KB)

MCP3424.h (2.14 KB)

MCP3424.cpp (2.49 KB)

12

I have a pressure transducer

Post a link.

13

Disconnecting ground of the A/D while it's inputs are grounded could damage the A/D chip.

Pressure sensors are usually ratiometric.
Not sure if you can get things stable if you measure that with a non-ratiomatric (absolute) A/D.
Leo..

14

outsider:
Post a link.

There are the ones provided by this company. It is run into a 9-pin VGA adapter

15

Wawa:
Disconnecting ground of the A/D while it's inputs are grounded could damage the A/D chip.

Pressure sensors are usually ratiometric.
Not sure if you can get things stable if you measure that with a non-ratiomatric (absolute) A/D.
Leo..

Ah okay. I did not design the board and I was skeptical of those who did. Does the board need to be redesigned with a new A/D chip without the inputs running to ground?

16

The MCP3424 draws 0.3uA in standby mode according to the datasheet.
You must have a very good reason to turn off the supply for that amount of current.

Don't know if you should be using a different A/D if we don't know what pressure sensor you're using.
Absolute A/Ds (like this one) are ok for sensors with current or voltage outputs, but not for sensors with ratiometric outputs.
Leo..

17

Attached are some schematics for a device I am troubleshooting. I am having trouble discerning how each section of the device is connected to the Nodemcu. I tried contacting the maker of the schematic but he has not gotten back to me in months.

The way the device is supposed to work is that a pressure transducer sends pressure data to the MCP3424 chip which converts that analog signal to a digital one, which can be read by the Nodemcu and translated into a pressure reading. I am unsure how each of these parts connects with each other. What pin is receiving the signal from the MCP3424? What do all the arrows that point to labels such as "adc_bm1" mean? If anyone has any suggestions on how the different sections of the schematic are connected, please let me know.

Thank you.

pcb_board_nodemcu_final_v2.pdf (29 KB)

18

I am having trouble discerning how each section of the device is connected to the Nodemcu. I tried contacting the maker of the schematic but he has not gotten back to me in months.

The way the device is supposed to work is that a pressure transducer sends pressure data to the MCP3424 chip which converts that analog signal to a digital one, which can be read by the Nodemcu and translated into a pressure reading.

I am unsure how each of these parts connects with each other.

What do all the arrows that point to labels such as "adc_bm1" mean?

First things first;
adc_bm and adc_bm1 are undoubtedly labels for Analog to Digital Converter /Battery Monitor
and Analog to Digital Converter /Battery Monitor_1, since adc_bm is the output of a voltage divider coming from the Lipo connector. Assuming the Lipo is a 2S , the charged voltage would be 7.4Vdc. The voltage divider is comprised of a 47k (probably because it is the closest standard value to 50k ) and a 100k resistor, resulting in an output voltage of about 3.5V, or
exactly HALF of a full charge. This is the MAX voltage that could come from that voltage divider with fully charged battery so no doubt this was chosen because it falls comfortably withn the range of any ADC running on 5V.

adc_bm1 only exists if jumper JP2 is moved to the other position, rerouting the battery Monitor voltage to the MCP3424 instead of going to the NODE_Mcu. Reason for that is unknown at this time.

What pin is receiving the signal from the MCP3424?

This would be an invalid question in view of the fact that ADC stands for Analog to Digital Converter and the MCP3424 clearly indicates CH2+/CH2- are positive and negative differtial analog inputs to the MC3424 , which , by the way is an IC2 based device and IC2 is Multiprocessor/MultiSlave bidirectional open-drain 512kbs serial digital so the there is no
"pin" associated with the output of the MCP3424. The output is sent on the bidirectional bus
via the SDA (Serial Data) and SCL (Serial Clock). The data is sent at about 500kbs and is bidirectional.
In order for you to use this circuit you will need to learn something about the I2C code syntax
MCP3424 I2C Sample Code

As configured in the given schematic, the MCP3424 is receiving pressure voltage on the CH1
DIFF input pins, converting it to digital and putting out on the bus where it is sent to the NODE_MCU and stored on the SDCARD.

The battery is monitored by the NODE_MCU, not the MCP3424 because JP2 is in position 1.

Any other questions ?

HOMEWORK:

  1. I2C
  2. I2C TUTORIAL

"You're either on the bus or off the buss..."
Ken Kesey

Is it possible you might be getting in over your head ?
It's fine to want to use electronic circuits that are so available today but there is such a thing as getting too far ahead of yourself. I suppose suggesting you learn electronics before using is
out of the question ?

19

Seems this is the third thread for the same project.

Reported the cross-post to the moderators.
Leo..

20

raschemmel:
First things first;
adc_bm and adc_bm1 are undoubtedly labels for Analog to Digital Converter /Battery Monitor
and Analog to Digital Converter /Battery Monitor_1, since adc_bm is the output of a voltage divider coming from the Lipo connector. Assuming the Lipo is a 2S , the charged voltage would be 7.4Vdc. The voltage divider is comprised of a 47k (probably because it is the closest standard value to 50k ) and a 100k resistor, resulting in an output voltage of about 3.5V, or
exactly HALF of a full charge. This is the MAX voltage that could come from that voltage divider with fully charged battery so no doubt this was chosen because it falls comfortably withn the range of any ADC running on 5V.

adc_bm1 only exists if jumper JP2 is moved to the other position, rerouting the battery Monitor voltage to the MCP3424 instead of going to the NODE_Mcu. Reason for that is unknown at this time.

This would be an invalid question in view of the fact that ADC stands for Analog to Digital Converter and the MCP3424 clearly indicates CH2+/CH2- are positive and negative differtial analog inputs to the MC3424 , which , by the way is an IC2 based device and IC2 is Multiprocessor/MultiSlave bidirectional open-drain 512kbs serial digital so the there is no
"pin" associated with the output of the MCP3424. The output is sent on the bidirectional bus
via the SDA (Serial Data) and SCL (Serial Clock). The data is sent at about 500kbs and is bidirectional.
In order for you to use this circuit you will need to learn something about the I2C code syntax
MCP3424 I2C Sample Code

As configured in the given schematic, the MCP3424 is receiving pressure voltage on the CH1
DIFF input pins, converting it to digital and putting out on the bus where it is sent to the NODE_MCU and stored on the SDCARD.

The battery is monitored by the NODE_MCU, not the MCP3424 because JP2 is in position 1.

Any other questions ?

HOMEWORK:

  1. I2C
  2. I2C TUTORIAL

"You're either on the bus or off the buss..."
Ken Kesey

Is it possible you might be getting in over your head ?
It's fine to want to use electronic circuits that are so available today but there is such a thing as getting too far ahead of yourself. I suppose suggesting you learn electronics before using is
out of the question ?

I appreciate the detailed response. I was originally brought on for this project to work on the code, so I thought gaining an understanding of the schematics would help me. I'll have to find someone who understands these concepts a little better. In the mean time, I'll read through those links.

I was originally brought on to just fix some code to allow the device to connect to the internet. I did that, but I saw that the device was not uploading real data, rather it was just sending random numbers from 1 to 100. I removed that, and am trying to figure out how to get the data from MCP3424. I tried using the code from the MCP3424 example, but it did not work.