Microcontroller based low cost safety alarm for straw management system attached to combine harvester

The super straw management system (SMS) is fitted at the back of the combine harvester and below the straw walkers. Thus, it is not possible for the operator to monitor the working of SMS. The rotor of SMS operates at a high speed (1800 rpm) and any reduction in the rotor speed can cause straw blockage in the combine harvester. The blockage of straw can damage/break the straw walkers of the harvester, which adversely affect the performance of the system. Therefore, to cope with this serious problem, an automatic low-cost safety alarm was designed to prevent the damage to the combine harvester and SMS. The safety alarm works in the range of 1000 to 1800 rpm of the SMS rotor. A microcontroller based on open source software was used in the safety alarm. The safety alarm consists of Arduino microcontroller, proximity sensor, relay module, and a light switch and 12 V battery. Two proximity sensors of different makes (8 mm and 4 mm sensing distance) were used to measure the rotational speed of the SMS rotor. The safety alarm triggers a light signal whenever rpm of the straw management rotor falls below 1000 rpm. A contact and non-contact type tachometer (make) having a least count of 0.1 rpm was used to compare speed of the rotor measured using microcontroller. The average variation compared to contact tachometer was 2.1% and 1.1% for sensor1, and sensor2, respectively. Similarly, the average variation compared to non-contact tachometer was 1.8% and 0.6% for sensor1 and sensor2, respectively. Therefore, proximity sensor2 (of 4 mm sensing distance) was recommended for use in the commercial version of low-cost safety alarm. The provision of safety alarm on the SMS attachment makes the system robust against potential threat of straw blockage, thereby, will increase the life span and rate of adoption of SMS attachment in the region.