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Abhijit Kshirsagar Kshirsagar 2022-04-27 10:22:37 +05:30
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Balu Mahesh
1. Design a system using a conductive water sensor (basically two metal probes that are very close together - when water is present between the probes it conducts) to detect when water level in a tank falls below 20% and when that happens, turn on a pump. The pump is a 3-phase 3-wire 1kW rated. This is for an industrial application where the water is being used for a chemical process. Design the system with some fail-safe such that the tank should never become empty.
2. Design summary is ok but could have been a little more detailed. Where is the fail-safe to prevent the tank from being completely empty?
How do you prevent overflow? How do you prevent the motor from running when input supply is not present? What about when the pump fails?
Basically there is no mention of the failsafe requirement.
What are the tadeoffs? How are you balancing cost, efficiency, and reliability?
What is the meaning of "Zero PCB or card board"?
3. Block diagram: what is roof of the tank? The top of the tank? Or is the tank on the roof of a building?
The block diagram is confusing: what is the meaning of "exception?" Which of thse lines are signal and which are power??
4. Power supply design is totally absent.
5. Industrial Design:
Your text is directly lifted from https://sg.rs-online.com/web/c/enclosures-server-racks/enclosures/pcb-mounting-enclosures/
6. KICAD Design
Schematic:
Did you use this circuit? even the values are identical: https://easyelectronicsproject.com/wp-content/uploads/2020/10/Water-Pump-Auto-Switch-Pic-12.jpg?x56667
PCB:
Layout seems ok
DRC is not passing because there is no outline.
7. Pricing / Assembly: Items costs are ok although grossly underestimated. No mention of materials for the actual probes, wiring, etc ???

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Name: Lokesh
1. Question text:
Design a system using this Honeywell ammonia sensor (https://drive.google.com/file/d/164WvPD7GauvseOfH-K3v8iZ4YYmQFkq-/view?usp=sharing )
to detect when ammonia concentration in ambient atmosphere exceeds 100 ppm an alert an operator in a control room about 100m away.
This device will be mounted in various sections of an industrial processing plant. The complete plant will need a fairly large number (~20)
of sensors so unit costs needs to be kept under control. Also, once mounted it will be very difficult to remove/service/repair the sensing devices.
2. Design summary:
Your design is well thought out. Using the cascaded power supply for local boards and wireless link to control room is also a good point.
In reality you will have to check if the industry allows wireless, which bands, or whether they want some MODbus type system.
One major issue in your design is that you are using a FET as the frontend - how will you account for variations in the FET gm? Each board
will have a different gain which you need to calibrate. Similarly each sensor has a different gain and sensitivity which you need to calibrate,
you should have mentioned that.
3. Block diagram
Block diagram is fine.
Some details are missing - for example what are the protocols / signal levels between the boards?
What happens when multiple sensors go off - are there some ways to tell the control room wchich sensors have gone off?
Or how many?
4. Power supply design
Why have you chosen a rectifier supply? Can you not choose an off the shelf switching sypply?
Are you gonig to supply different PSU for every different voltage level in industry?
5. Industrial Design:
Mostly ok - dimensioning could be better. Also, are there wires coming out of the box?
Or are there connectors on the edge? or are there some cable glands?
6. KICAD Design
Schematic:
Major flaw in circuit design - your 5V regulated is not ground referenced. So any noise / disturbance in the power line will make it into the output.
PCB:
Board outline is missing and DRC fails
Why mix SMT and THT components? Also interesting that your THT components are on the back. Why?
Some unconnected stubs on your board - e.g.
7. Pricing / Assembly