To my surprise such a thing is still not available as a DIY kit / solution, though technically a rather simple thing methinks
.So I'd like to share here my slow steps of developing hardware and software in the frame of a new e-bike build of mine, that will be composed of a stripped down gear hub motor driving a Rohloff gear hub. Pedals and motor will have their own dedicated chains, directly driving the Rohloff for both to take advantage of the gear hub. I will cover my build in a separate thread. My mechanically solutions for the electronic gear shifter will therefore concentrate on interfacing with the Rohloff Speedgear.
That's just to give some background here.
Code: Select all
/*
Electronic gear shift for Rohloff Speedhub and others gear hubs
Arduino Nano V3 ATmega328 (old bootloader)
Testversion for 270° Miuzei 20kg Servo
500-2500usec => 270°
Rohloff Speedhub axle on external gear box needs a full turn of 360°
to shift from gear 1 to gear 14
360° => 27,6923° eg 27,4074usec>/° each gear => 2000usec => 500 - 2500usec
//
to shift 10 gears on Rohloff Speedhub
=> 249,231° => 27,6923° eg 27,4074usec>/° each gear => 1384,62usec => 807,69 - 2192,31usec
real calculated usec range for 10 gears on Rohloff:
808 - 2191usec due to finite INT calculation accuracy
Rohloff speedhub electronic gear shift by Arduino servo
2019 written by "endlessly_ending" at endless-sphere
*/
#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
#include <Servo.h>
Servo motor;
//--------------------------------------------
int ButtonUp = 8; // button for up-shift connected to Arduino port 8
int ButtonDown = 7; // button for down-shift connected to Arduino port 7
int count = 1; // gear index
int LastCount; // last gear index
// int MaxGear = 14; // gear count for Rohloff Speedhub
int MaxGear = 10; // TEST setup for <270° servo => 10 gears at maximum possible
int MinGear = 1; // first gear
int GearStepUsec10; // 10x gear step usec to improve calculation accuracy
int StartGear = (MaxGear - 2); // start out at two gears down
int Motor_Stop_LED = 13; // LED indicator when motor is on halt, LED and relays connected to Arduino port 13
int AngleUsec; // index angle in usec
int AngleUsecMax; // max index angle in usec
int AngleUsecMin; // min index angle in usec
int FirstGearIndexTrim = A3; // trimmer for adjusting first gear index connected to Arduino port A3
int PlayComp = A2; // trimmer for compensating shift gear play connected to Arduino port A2
int FGIT; // variable to store the value read of FirstGearIndexTrim
int PC; // variable to store the value read of PlayComp
//--------------------------------------------
void setup()
{
Serial.begin(9600); // TEST use the serial port to print the number
digitalWrite(Motor_Stop_LED,HIGH);
lcd.begin(16, 2);
lcd.print(" initialize ");
lcd.setCursor(0, 1);
lcd.print("motor on halt");
pinMode(ButtonUp,INPUT);
pinMode(ButtonDown,INPUT);
digitalWrite(ButtonUp,HIGH);
digitalWrite(ButtonDown,HIGH);
pinMode(Motor_Stop_LED,OUTPUT);
count = StartGear;
motor.attach(9);
pinMode(A2, INPUT_PULLUP);
pinMode(A3, INPUT_PULLUP);
delay(1000);
digitalWrite(Motor_Stop_LED,LOW);
}
//--------------------------------------------
void loop()
{
// set start conditions and read status of up shift and down shift button- 190831_electronic_shift_Rohloff_V15_TEST270_V5.jpg (92.4 KiB) Viewed 3101 times
As can be seen, the Arduino code will allow for easy editing of
- gear count of what ever gear hub one wants to use
- adapting for different servo motors
- electronically fine adjusting gear one end position
- electronically fine adjusting to compensate play in the shift gear mechanics
- make use of standard RC or robot servos of any kind that can be controlled by PWM signals
As for now, my testing is limited by the restrictions of a 270° angel range of the otherwise nice Miuzei DS3218 servo
https://www.amazon.com/Digital-Waterpro ... s9dHJ1ZQ==
Its not easy to find a widely available servo of moderate price, that combines a angle range of +360°, quick response with strong force and is more or less waterproof.
Nevertheless I have a Kingmax sail winch servo in the pipe, that possibly could do the trick.
