WEIGHING SCALE – SMART SYSTEM

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This is a prototype done as a model for PLC implementation for weighing bridge scale to ease out for trucks or other heavy vehicles.

It houses a bunch of sensors like wheel sensor, infrared wheel separator to smoothen the entire process. The weight measure is displayed and the toll hand(if that’s what it’s called) moves 90 degrees up or down to allow and stop the vehicle respectively with the help of a servo motor.

The picture below is prototype I made.

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Inbox me for the codes.

DRV 8255 vs A4988

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While I went on to explore the most suitable module to control my stepper motor. Preferably for a CNC machine, and many promising contestants showed up. Contestants include l293d, TB560, DRV8255, A4988, Rees52 This blog decides the winner.
IMG_20170504_143045

The good looking(DRV-8255) on the left is surely attractive and there doesn’t stand much difference when it comes performance with the A4988. The screw type adjustment to control the current limit is the same both the modules and might look different than yours as there are multiple chinese manufactures. Where aren’t they? Really? Handle the trim pot gently or else you might end up ruining the module

Heating was very common on both the IC’s which can be pulled down to an extent with additional usage of sink and fan cooling options. The A4988 seemed to cool off much faster when motor is not in operation. The polou IC is technically more reliable on paper. A4988 IC is tiny and might come off under intense heat and rugged usage.

On the programming front, The libraries were available combined for both of them and looked equally comfortable.

Mixing of both A4988 and DRV8255 worked fine on the CNC module. The availability of both in market is not the same, as drv8255 were found almost everywhere. And my observations below.

 

A4988 DRV8825
Availability very widely available widely available
Approx. price 225RS 185Rs
Max. theoretical current 2A 2.5A
Max. microsteps 16 32
PCB color Green / Red Purple
Stepper current adjust. trimpot Yes, near Dir pin Yes, near En pin
Typical Rs value 0.05 Ohm or
0.1 Ohm or
0.2 Ohm
0.1 Ohm
Vref formula (*) I_TripMax= Vref/(8*Rs) I_TripMax= Vref/(5*Rs)
Thermal Overload Protection (**) Yes Yes
PCB layers 2 4
Small heatsink included (***) Almost always Sometimes not
Active cooling required? Recommended Recommended
IC packaging 5x5mm 28-lead QFN 9.7×6.4mm 28HTSSOP

The judgement? Well . . .

A4988 wins. But, not by a fair margin.