6DOF Prototype using small dc motors

Hello Folks,

I'm building a prototype of 6DOF simulator using dc motors and rotary encoder instead of regular pots/hall effect sensors. I’m using the SMC3 software as a reference, and building my own software based on the SMC3, but just for 2 motors and 2 rotary encoders, also using freeRTOS with tasks and a nodeJS server that receives the SimTools UDP packets and send through the serial port to Arduino Uno.

My Setup:

· 6x Small DC motors (3-6v)

· 6x Rotary Encoders (KY-040)

· 3x L298N boards (H-bridge)

· 12x Mini kossel spherical joints
· 3x Arduino Uno


I’m planning to use just one pc to handle everything, pc settings:

· Intel i7 7700K @ 4.5 ghz

· AsRock z270 PRO4

· 8gb Corsair Vengeance DDR4 @ 3000 mhz

· Gigabyte GTX 1070 8gb

· 2x 128gb SSD Samsung Pro 840 @ Raid0

· Logitech G27 Gaming Wheel

· Stockcar Cockpit for G27


I’ve updated the SMC3 software to use the rotary encoder instead of the pots.

Here is the info regarding the rotary encoder: http://henrysbench.capnfatz.com/hen...es-ky-040-arduino-rotary-encoder-user-manual/


The Rotary Encoder has a total of 30 rotations, it means 30 rotations = 360 degrees

1024/30 = 34.13 per rotation on a total range of 0 – 1020 for 360 degrees

Limiting the rotary encoder rotation to 180 degrees: 1024/15 = 68.26 per rotation on total range of 0 – 1020 for 180 degrees.


The feedback seems to be working fine with the rotary encoder, but it seems that the dc motor gearbox has a lot of slack, something is wrong:



Now testing the Axis1a using the SimTools Output Testing:



I would like to have your opinion about the feedback using the rotary encoder, what is wrong? The code is attached.
Also, I need to use something to get the current position of the rotary encoder after power on/down, some type of calibration based on the min/max angles, maybe using 2 sensors for min/max angle to calibrate the rotary encoder and go to center position.

Code used for the rotary encoder:

initEncoder(MOTORA_CLK, MOTORA_DT);

//Feedback1 = analogRead(FeedbackPin1);
Feedback1 = encoder.currentValue;

What type of motors do you use ? Do they have a gearbox ?

Yes, he has a gearbox on his small motors (see his first picture - gearbox in yellow). I'm not surprised that they have some slack . You could use limit switches and some code for initial calibration.

Hi @Gadget999

I'm using small DC motors with built in gearbox and double axis:
https://www.ebay.com/itm/DC-3V-6V-G...hash=item54519df339:m:m_230QMDdjdb2G5AGe9kCLQ

The motor has about about 90 rpm and a gearbox of 48:1



Those gearboxes have a lot of slack, I can feel it with my fingers..

My rotary encoder direction was inverted, it was causing initial failure of the software with invalid feedback values.. And I thought the problem was the L298N board
The range of SimTools axis is just 100-923, why? Shouldn't be 0-1024?
I'm planning to use Optic Sensors TCRT5000 as limit switches, I will test the min range of them and check if they work as expected.

First test of the motor after some regulations:

I bought 2 monster motor shields, lets see if I have lucky with them.

The first board has poor soldering on the chips and a short circuit ping soldering on one of the chips. Also I can't even read the chips info.
The second board looks better, I can read the chips info and the soldering is better.
I will test the second board and re-solder some pins of the first board.

Can u help with connection h bridge l298n to arduino, i am complete noob and try to find how a lot time and cant find