diff --git a/Chirag/Comments.txt b/Chirag/Comments.txt new file mode 100644 index 0000000..0273e1c --- /dev/null +++ b/Chirag/Comments.txt @@ -0,0 +1,43 @@ +Name Chirag + +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: + Summary is ok. The current change is not fixed - you need to calibrate it - you have overlooked that. + On the receiver side, how do you check which sensor(s) have triggered and/or by how much? + Also, how do you handle the return lines for each sensor? You are powering all the sensors using separate isolated supplies! + +3. Block diagram + System design is ok. + Lots of issues have been glossed over - what if one sensor (or its PSU) fails? + The current change is *extremely* small per ppm. What is the final current change and how do keep it immune from noise, drift, errors? + We discussed so many issues in class but your circuit has not even a mention of them? + +4. Power supply design + Why use the same transofmrer for both 5V and 15V? Won't you have immense losses using a 15V transformer and 7805? + And even for 15V, your 24V rms secondary will give you far higher voltage than you need - headroom for 7815 can be nominally + 5-7V even on a worst case basis to account for supply dip. + +5. Industrial Design: + What is "pull" marked on the sensor box? + +6. KICAD Design + Schematic: + Your part 1 has only the power supply. Where is the connector for the sensor? + Part 2 needed to be scalble - since all your processing is being done on this board you will have to make a 20 opamp version + irrespective of how many are actially deployed. + Why have you not used the correct symbol for OmAmp? + + PCB: + Layut is good overall. + You have a 6pin SMD footprint for the line-frequency transformer - this shows a very cavalier approach to this design. + DRC fails on both designs, no outline. + Why is the LED pointing inwards? How will it be seen? + Your industrial design diagram has multiple "LEDs" but only one LED in the design. + No power supply indication? Power On LEDs?? + + +7. Pricing / Assembly + There is no pricing information in the BOM and therefore no concrete justification for unit cost.