First stepper motor project

Thread Starter


Joined Nov 16, 2011
Hi all,
First post here as I've just started a project to build a custom speedo/tacho for my bike using a dual-concentric shaft stepper motor.

I've chosen to drive each motor directly using a nanotec SMCI12 as my software development skills are far better than my knowledge of discrete component electronics.

The simple motors I have have physical limits restricting rotation to about 300 degrees and, for limit sensing and calibration, I'm currently using a pair of hall effect sensors mounted on the clock face being triggered by tiny magnets mounted under the gauge needles. The outputs from these are poleed from witin the controller program and allow for a reference run at start-up.

Whilst this works I was wondering is there's a simpler way to detect the motor reaching the hard limits and calibrating that way? I've read that reading the change in back-EMF can be used but not sure if that's a reliable option and also whether it could be detected from within the controller software I'm using (NanoJEasy).

Many thanks for any replies.



Joined Jul 17, 2007
Hello, berniej,
Unfortunately, you're in trouble right off the bat.
SMCI12 temperature range is: 0°C - 40°C
Automotive temperature range is: -40°C to +125°C

The SMCI12 is not suitable for use for an automotive application. It doesn't even meet commercial temp specifications (0°C to 85°C), and automotive specs are much more demanding.

To put it simply: if you use it, it will break.

Also, there is a Terms of Service on the Board, and a portion of it states:
6. Restricted topics. The following topics are regularly raised however are considered "off-topic" at all times and will result in Your thread being closed without question:
  • Any kind of over-unity devices and systems
  • Automotive modifications
  • Devices designed to electrocute or shock another person
  • LEDs to mains
  • Phone jammers
  • Rail guns and high-energy projectile devices
  • Transformer-less power supplies
Automotive repair topics, where a function is being restored to manufacturer's specifications is a different matter.

However, you are wanting to change from an existing proven reliable system, to another one that does not meet the minimum requirements for operating temperature range.

Over in our Electronics Resources forum, there is a thread with some member-selected forums where you might discuss this project:

Because of the way our Terms of Service is written, I'm afraid that your project is a bit beyond the scope of our Forum.

Even though our discussion here will be ended, please keep in mind the automotive temperature range limits.


Joined Sep 20, 2005
Bike as in motorbike or bicycle?
Anyway, you could just know the number of steps it can do, and always move the motor that number of steps towards one end to make sure it is reset.


Joined Nov 25, 2009
I 'll ask the same question as kubeek. Motorbike or bicycle?

I 've always had trouble telling which is which. All of you English speakers, where does bike refer to? Is there an age context factor?


Joined Jul 17, 2007
"Bike" can be used to refer to either a pedal bicycle, or a motorcycle.

However, while a speedometer could be useful on a bicycle, a "tach", "tacho" or "tachometer" would not be useful, because a bicycle does not have an engine like a motorcycle does; in the case of a bicycle, the human is the engine!