CURRENT SENSING MECHANISM USING MICROCONTROLLER

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CURRENT SENSING MECHANISM USING MICROCONTROLLER

SYSTEM ARCHITECTURE 
Complete system architecture is presented in Fig. 1 which includes single master and master’s slave scheme. The slave is connected with machine and station light. Whenever the worker starts the machine, slave senses the machine current and turns ON the light and optional fan for a specific period of a time. ON light status is adjusted through programming. Master slaves communicate through RS485. The entire master’s takes data from all the connected slaves and sends it to the single master, afterword single send data to receiver using a wireless transmitter. A receiver receives the data and sends it toward the managerial computer. Data gets processed at the receiver end which sends it to the computer through RS232. If the system is turned off, then data will be saved in EEPROM. The data gets transmitted, when the computer turns ON. Moreover, data is saved in excel file.
CURRENT SENSING MECHANISM 
The basic principle of the circuit is comparing the current of machine with supply line current by converting into voltage using lm324 voltage comparator. When machine starts working then flux around the supply line change, this change of flux induces some amount of voltage certainly detection of current give signal to relay to operate turn ON the light [11, 12] Pros and cons of this current sensing mechanism xThere is no wired issue. xThere is no sensor which can hurdle into work. xThere is no sensing area issue. xThere is no cost issue.xEasily to install. xAnalog components will be used, which efficiency decreases with time. 
  A.Module Design Sewing machine draw a 0.8-amp (tested value) current on working state. So, we compare the current of the machine with predefine value (0.8A). https://vssewingmachine.in/ One leg of C.T connects with supply and the other one with machine supply. Machines current flow by pushing the feet on paddle, current is sensed through C.T. Some amount of voltage induces, phenomenon explains above. Our circuit working in D.C level so we rectify the current using diode and capacitor. We will do half wave rectification because using half wave rectifier voltage drop across the diode is 0.7V and if we use full wave rectifier drop across the diode will be 1.4V. If that is so, voltage drops across diode increases due to it sensing voltage can’t detect. The reason is that our current sensor is current transformer and voltage across C.T. is very low, where very low voltages produced. The measured voltage across the diode is 0.32V at 100Watt load. Polar capacitor connects parallel to diode and C.T for improving transient response. Resistor connects parallel to capacitor for improving discharging time of capacitor and its make R.C circuit. We can change the time using variable resistor. We used lm324 comparator for voltage comparison. We adjust the 0.25 voltage at inverting input pin 2 using voltage divider rules for comparison. Sensor (RC circuit) output will go to lm324 pin 3 which would be 0.45 volt. If the value of voltage below adjustable voltages the output will be zero otherwise one. When sensor output high it will trip the relay and relay will turn ON the light. But the problem is that it will be for momentary. So, we use another comparator. The output of one comparator will go to non-inverting input (pin 5) through RC circuit and the diode. Resistor and capacitor connect parallel with diode and pin 5 of lm324. A resistor is used for increasing the discharging time of the capacitor and diode use for resisting back flow of current. When output of one comparator is high the capacitor will charge and the diode will resist to slow discharge or back flow of current. Second comparator output will connect to relay and relay will be higher until the capacitor discharge. We can adjust the timing using RC circuit.

CURRENT SENSING MECHANISM USING MICROCONTROLLER
 Microcontroller is a mandatory requirement because we are using MAX RS485 for master slave purpose; wireless regenerative transmitter and receiver as well as data also need to save. All those reasons, we shifted towards the microcontroller. Moreover, our circuit area is also reduced. We can use delay using microcontroller which is more reliable.
A.Slave Working Main supply to comparator circuit is same which elaborate above. Comparator output goes to microcontroller pin. Controller continually checks the P0.4 pin. When the output of the comparator will high, then the controller will give signal to P1.6 pin at the base of the transistor 2222 switch. Transistor gives the signal to 5V relay and relay will turn on the light. When the lights turn ON, it means worker start working and starting status is sent to master using MAX485. Whenever the machine turns off, the output of comparator gets low. But controller continually gives a signal to relay according to delay. Delay is adjusted according to desire. When delay finishes, the controller checks the status of the machine and if the machine still not operating then relay signal get low and light will turn off. When the lights turn off then controller again send a signal towards master using RS485. 
B.Master Working Master requests the machine status from slaves after every adjustable time. Slaves send its status to respective master through serial communication MAX485. Master saves machine status and its time using RTC (DS307). Then every master sends data towards the single master on the requested time. Single master sends data to receiver end using R.F (super regenerative module) transmitter and receiver, Data receives through R.F receiver and send data to computer through USB terminal and saves data to excel sheet. If single master didn’t respond then master save data into its memory then transmit upon ask, similarly, if the receiver doesn't respond, then the master will save data into its memory. 

RECEIVER WORKING 
Receiver circuit receives the complete working status of masters through single master. For beginning the transmission, master send the signal to communicate, and then receiver reply back to master that you can communicate, then receiver receive machine status through R.F receiver and sends it to computer USB terminal through max232 [15]. If the computer doesn’t respond, then receiver saves data into its memory. When the system responds, then the data send to computer through USB terminal and remove data from its memory. Data will save into excel sheet using the front-end design application.    
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