DarkMatter
New member
Hi all, first post on here so be gentle!
Right some background: I am a web developer, I haven't played with the likes of Teensy / Arduino etc before though.
I am currently rebuilding a classic MG Midget with a Zetec engine and want to find a way to drive the original speedo, for those who are not into cars, the older speedos were connected via a spinning cable to the gearbox which transmits a turning motion into the gauge.
As I am putting in a later style gearbox which has no way to connect this, I want to make up a little device that can turn this cable electronically.
So my plan is:
- Hall-effect sensor somewhere on one of the wheel hubs with a magnet on (for example) the brake disk.
- connected to a Teensy (how?)
Given I can calculate the speed from the rolling radius of the tyre, I can instantly know the speed of the car in code.
- Teensy then drives a stepper motor at a speed (speedo input rpm to displayed speed will need to be investigated, but it is linear)
So, What I need is to:
A: Get the Teensy to accept a signal from a Hall sensor.
B: Figure out the current speed in code
C: Figure out what speed the stepper needs to be spinning
D: Power a low-power stepper.
I can of course adjust the measured road speed to stepper speed calculation as needed, but first I want to see if this is feasible and what I'll need to get going.
I could actually use a variable resistor to change that on-the-fly, to tune via GPS.
Voltage-wise in the car it will be variable as engine off will be about 12.5-12.8v and running will be around 13.8, so I will probably use a 5v output regulator (a USB car charger circuit for example)
The aim is to build this into a small box that can be mounted in the dashboard or even better (if small enough) into/onto the gauge itself.
Right some background: I am a web developer, I haven't played with the likes of Teensy / Arduino etc before though.
I am currently rebuilding a classic MG Midget with a Zetec engine and want to find a way to drive the original speedo, for those who are not into cars, the older speedos were connected via a spinning cable to the gearbox which transmits a turning motion into the gauge.
As I am putting in a later style gearbox which has no way to connect this, I want to make up a little device that can turn this cable electronically.
So my plan is:
- Hall-effect sensor somewhere on one of the wheel hubs with a magnet on (for example) the brake disk.
- connected to a Teensy (how?)
Given I can calculate the speed from the rolling radius of the tyre, I can instantly know the speed of the car in code.
- Teensy then drives a stepper motor at a speed (speedo input rpm to displayed speed will need to be investigated, but it is linear)
So, What I need is to:
A: Get the Teensy to accept a signal from a Hall sensor.
B: Figure out the current speed in code
C: Figure out what speed the stepper needs to be spinning
D: Power a low-power stepper.
I can of course adjust the measured road speed to stepper speed calculation as needed, but first I want to see if this is feasible and what I'll need to get going.
I could actually use a variable resistor to change that on-the-fly, to tune via GPS.
Voltage-wise in the car it will be variable as engine off will be about 12.5-12.8v and running will be around 13.8, so I will probably use a 5v output regulator (a USB car charger circuit for example)
The aim is to build this into a small box that can be mounted in the dashboard or even better (if small enough) into/onto the gauge itself.
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