RPi – A4988 stepper motor driver

The A4988 is a stepper motor driver board that has on a A4988_chip that enables control of stepper motors through arduino type programming firmware and software.
The A4988 is an utterly tested and proven solution to drive stepper motors in RepRap 3D printers, and this fact should not be overlooked. As long as the following three conditions are met, these Made in China Allegro A4988 stepper driver boards seem to be bullet-proof workhorses:

  1. The stepper driver boards should not be inserted backwards in their respective slots on the controller board.
  2. The stepper cables should not be disconnected from the boards while powered on.
  3. Proper airflow (i.e. active cooling or in other words, a fan) should be provided.

The alternative DRV8825 board, with increased 1/32 step mode is slightly more expensive.

Both the the A4988 and DRV8825 boards are interchangeable (note how you put them in), and should work the same on any 3D printer or similar system.

The following table compares Made in China A4988 Stepper driver boards vs DRV8825 ones, for RepRap use:

A4988 DRV8825
Availability very widely available widely available
Approx. price $6.80 / 5 pieces $10 / 5 pieces
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



Anycubic I3 Mega – dual watch winder

This is a 3D printed double watch winder which powered by a 3K1655 gear motor which powered by a 5V usb power supply from any mobile phone and controlled by an external 7 days x 24 hours programmable timer.

In order to protect and hold the watches in place, flexible pad was made from the insulation tube for the hose of air conditioner. There is a wide range of size for your choice.

Hints and tips for using a watch winding:

  1. Timer turns on at intervals (i.e. At least 3 times a day) which noise of motor/gear was not interfering your daily living and stored in a place with stable temperature and humidity (i.e. Stored in a enclosed cupboard and placed over a absorber);
  2. The USB power supply (i.e. Use good quality 5V power supply) shall be safe to operate without hazard of fire;
  3. All the watches can be winded properly and ensure that it can be used by you at any time without adjustment of time (i.e. Set the time correctly at first and then hand winding/swing until it is moved prior to insert onto the cups of winder. ;
  4.  It must be secured hold in the cups of winder without falling off from the winder (i.e. Use correct size of pad to suit your watch. If it is possible, please set the winder in inclined position to prevent rolling out of watches) during prolong winding for months.

Anycubic I3 Mega – print size hacks

With below modifications, size of printing was changed to  210 x 210 x 233 mm. First of all, the gantry was risen and the connector of hot end and cooling fans were relocated to back of lead screw.

  1. Gantry was risen by (i.e. 28 mm) fastening two screws instead 4 screws and lowered down the end stops of Y-axis carriages.

2. Connector for cables of two cooling fans and hot end was relocated to back of slides with the below connector enclosure and a stool. 3. Machine setting in Cura shall be changed and Marlin firmware shall be used. Search in Configuration.h for Z_MAX_POS 206  and change it to 234 (i.e. 233+1) https://www.youtube.com/watch?v=6Urru7IsFrI