Monday, 25 August 2014

Lab test and real time project side tests

Lab/office tests and real time project site tests - the basic difference
It was i think our 5th trip to the greenhouse where we are implementing our greenhouse/polyhouse intelligent systems for internal climate control as well as real time monitoring of the variables. We have been testing our systems religiously in our office set-up which include testing and calibrating sensors, testing the PID loop which we had implemented, running 3-phase motors with our systems and off all testing the whole set-up which we are building. 

But when we tested the same set-up on the client side, we realize the needness of getting on the road when you are building some thing from home and that too in the field of Embedded system, you cannot simply rely on the office test-set-up conditions and believe that system which we had build is robust, reliable and will work in every conditions. Believe me, real time conditions on any site where we are going to install our system very much vary from what we had in our office set-up. Below are certain examples of what i experienced while installing one of the Intelligent humidifier in the greenhouse in Bangalore along with my boss. 

  1. Sensor Calibration : We a using a humidity sensor in our project that is highly accurate and we had got certificate of calibration from the manufacturer with respect to the  calibration. We tested the same sensor in our office with the help of a humidifier which was making too small water droplets varying from 5 micron to 10 micron that would ideally increase the humidity while when we were in greenhouse, we faced that the droplets which their fogger/sprinkler were making were much more bigger than we assumed and that is why they settled on the ground very fastly resulting in dropping the humidity level. Along with that as we had kept our humidity sensor inside a filter so that it measure humidity and not the water vapor. But we had kept our sensor with filter directly exposed to the fogger, water particles accumulate on the outer-filter and thus even though fogger was turned off, our sensor was still measuring increase in the humidity. This give us a sense that we don't have to expose sensor + filetr directly to the fogger. Also we came to know that greenhouse need to use low volume foggers. Also in the evening if the soil is wet due to over-fogging, water will evaporate which will result in the increase in humidity measured by the sensor.
    Foggers in greenhosue/polyhouse
  2. Length of I2C sensor wire:  while being in office, we were not thinking in the direction that we even will be require to extend the length of the i2c sensor wire that we are using in our solution. At present we were only working with a sensor wire that is only 22 ft long and while we are implanting this thing in a greenhouse, we will always think of cost optimization for both, for our organization and for the end costumer. As a i2c line can accommodate 128 sensors, a person can add 128 sensor(well i cannot and i will never try!!!!), but still with our 1 data-logger, we can atleast add 10 sensor with different i2c address, can place them in 10 different chambers in a greenhouse and can thus control 10 different systems to maintain respective chambers variables. Well in order to use 1 data-logger, we will be required to use long i2c sensor wire. Well this thing arise , when we were in process of testing our solution at client side. Well there are certain ways with which you can extend the length of i2c sensor wire to 10-20 meter and certain by which  you can extend the length to 100 meter.  
    Generally Greenhouse/polyhouse chambers are big and sensor need to be placed in different positions
  3. Heating issues :  Inside a greenhouse/polyhouse, temperature is generally high. So when we were working inside the greenhouse and my boss was writing down some code for simulating the environment, i saw him dipped in sweat, just because of the high environment. At that time, i though of the case of using less heat emiting parts in our pcb, like linear voltage regulators etc. 
There were certain other issues that occur like low power consumption and wireless requirement. We are already implementing wireless solution in the same greenhouse and my previous post on the same. And as per the low power requirement, PCB iteration-2 is already on its development which will have micro-controller running on 3.3 volts. I hope that i will update soon with respect to the new iteration of PCB and further progress on the WSN implementation. 

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