Task #3706
open
Flipkart - Cold room monitoring
Added by Thomas Joseph 2 months ago. Updated about 2 months ago.
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| clipboard-202607081630-hj7zo.png (140 KB) clipboard-202607081630-hj7zo.png | Sumanth D, 08/07/2026 11:00 AM |
Updated by Thomas Joseph 2 months ago
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#1
- Status changed from New to In Progress
Updated by Thomas Joseph 2 months ago
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#2
We cannot use an NTC sensor to PT100 transmitter
at 18deg. NTC resistance is 13KOhm, but PT100 has only 107Ohm.
the transmitter will saturate to 20mA always
Planned to to buy https://robu.in/product/0-5m-b3950-10k-1-ntc-thermal-sensor-rs485-modbus-rtu-serial-port-remote-acquisition-module-plc-12v/
continue testing on Monday
Updated by Thomas Joseph 2 months ago
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#3
Customer meeting (google meet)
Venkatesh, Manoj
Dashboard screens explained
--interested in compressor performance monitoring
----identify sensors to install
Updated by Thomas Joseph 2 months ago
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#4
- % Done changed from 10 to 20
Evaluated NTC to 485 module using modscan tool in lab
Got correct temperature results
Updated by Thomas Joseph 2 months ago
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#5
- % Done changed from 20 to 30
Design of NTC parallel connection for demonstration
Buffer to Tracker V3
ADC, Modbus server, LUT
Updated by Thomas Joseph 2 months ago
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#6
Testing of NTC circuit and discussion with HVAC consultant
Updated by Thomas Joseph 2 months ago
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#7
NTC to Teperature conversion from AI generated code. Computation tested. Evaluated in excel sheet.
TV3 AI (CH0) section reworked to accommodate NTC voltage from Dixell unit
Updated by Thomas Joseph 2 months ago
· Edited
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#8
- % Done changed from 30 to 50
Summary:
1 With OPA4991 buffer, max offset is 4mV to 5mV to ADC
2 This offset is causing max 0.1°decrease in TV3 485 measured temperature
3 The buffer does not cause more than 1mV change in the NTC voltage. Hence, Dixell reading will not affect
ToDo: Proceed for installation and Testing at customer site
Updated by Thomas Joseph 2 months ago
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#9
ADC fluctuations and Modbus time-out
need to add filter + ADC averaging
Updated by Thomas Joseph 2 months ago
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#10
Updated design => https://elpisit.sharepoint.com/:x:/s/EmbeddedFiles/IQBlYFGWAZvGR5o1vUKK73vzAY4oreOMitPe31w92YsHU4Q?e=IUtoSZ
Test with
Input volt source = 5V
use resistor divider of 1K and 3.3K
then jumper+560Ohm in parallel with 3.3K
with jumper closed, 1.6V
with Jumper open, 3.8V
At ADC input, .8V and 1.9V respectively
Updated by Thomas Joseph 2 months ago
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#12
- Project changed from 13 to Ad-Hoc Design and Development
- Due date set to 10/07/2026
- Assignee changed from Nagaraj C to VenuMadhav S
Updated by Thomas Joseph 2 months ago
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#13
- % Done changed from 50 to 70
7/7/2026
Tested at customer site
Conclusion
Refer "ADC-Temp" Sheet
1 Either a PU Voltage ofv5.15V or a PU Resistance of 5050Ohm for V_ntc of 3.65 with R_ntc of 13700Ohm
2 Taken measurements with R_ntc = 2355
3 Confirmed that PU Resistance is 5050Ohm
4 With R_ntc=2355Ohm, the displayed temperature is 67.9, excelsheet shows 39.8 but sw shows "CH0 | ADC = 10471 | Temp = 58.43 C | Modscan reg(40001) = 584"
ToDo
1 Identify the difference in temp between excel calc and sw calc
2 Check with known sensor with beta, R0, T0 available
3 Extend to 2 more sensor channels
Updated by Thomas Joseph 2 months ago
· Edited
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#14
Updated worksheet => https://elpisit.sharepoint.com/:x:/s/EmbeddedFiles/IQAtap3e-GFlRre3FdsXjvF9AUnZ5WZe7Bz4qDPhY2eExq0?e=fxpGPr
Production plan
- use L21 32pin package (rs 300) or STM32G030F6P6TR (<Rs. 100), 4 channel on-chip ADC
- smallest PCB with low cost enclosure with rev. pol/OVP/TVS/485 isolation+TVS, LDO
- low cost enclosure (< 150)
Updated by Sumanth D 2 months ago
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#15
- File clipboard-202607081630-hj7zo.png clipboard-202607081630-hj7zo.png added
- Assignee changed from VenuMadhav S to Sumanth D
- % Done changed from 70 to 50
In Tracker V3 rework was completed for 4 channels as shown in the attached rework image.
https://elpisit.sharepoint.com/:x:/s/EmbeddedFiles/IQAtap3e-GFlRre3FdsXjvF9AUnZ5WZe7Bz4qDPhY2eExq0?e=cE4dt9 - Rework sheet
Updated by Sumanth D about 2 months ago
· Edited
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#16
https://elpisit.sharepoint.com/:x:/s/EmbeddedFiles/IQBarbil0XJ_Qaa9KI8PQDdrAfs2WWaxD4G4buXHVc2jiJ8?e=8rrkwq - Block diagram
https://elpisit.sharepoint.com/:w:/s/EmbeddedFiles/IQBK3Fho9fO6QqC6hxm2wwChAeCF7z5nuwSG6E4VxrCOe9w?e=Ya9UxF - PRS in draft stage.
Created a Block diagram and PRS for New design.