Hall effect speedo for newbie

Hi all I've had a look on other peoples projects and can't seem to find what I want ( I'm new to arduino stuff so may have overlooked stuff ) Right What I want to make is a arduino based speedometer that can display speed on x2 3" 7 segment displays (speed will not be over 99mph) using a hall effect sensor as a trigger and with a working voltage of 11-14vdc

My problem is I have never even picked up an arduino let alone know what parts I would need to make it all work as the 7 segment displays I have seen are 24vdc and the arduino I was looking at uses 5vdc.

If anyone can point me in the right direction or let me know if a kit exists I'd massively appreciate it.

Thanks in advance Kind regards Eddie

If 1 sensor and 1 magnet your problem will be inaccurate reads while changing speed especially when going slow.

It is best to not buy until you know what to buy for sure.

Hi yes I currently have a small bicycle computer reading speed which has a single magnet and reed switch, this below 12mph is useless but has not proved a problem as I only need to read between 15mph and 88mph. I figured a hall effect switch would be more reliable (not sure what cycle life the little reed switch has)

If I could fit a larger screen to the cycle computer I could live with it but would prefer to use a couple of 7segment displays to be in keeping with the rest of my test gear.

I just need a small amount of guidance to make sure this is feasible option and to what parts I would require

Kind regards Eddie

I used to spin, I drafted trucks. I built wheels with stainless steel spokes just so they wouldn't come apart at around 70mph like steel-spoke wheels have been known to do.

A cheap Hall Switch (not linear sensor) will give you quicker and cleaner response than a reed switch.

Is your magnet on the front wheel hub with the reed switch on the fork? That's the place for it, close to the axle. What you do is add magnets around the hub, maybe 6 or 8 total since your code will be reading them. If you don't use super magnets you can likely get more to work, not keep the Hall "closed" all the time.

A 27" wheel goes about 7 ft per rev. 88mph is 18.43 revs per second for that wheel. Even with 8 magnets that's only 147 pulses per second (with the switch, the length of the pulse also tells speed) which is > 6 milliseconds apart, slow for Arduino.

A gear-tooth counter might be able to read spokes but needs more power and costs more than 10x as much.

Hi I should probably give some background to back up what I'm building This is to measure the tyre stretch experienced on car wheels when put under excessive load I've had to build a new rig to test 18" and above wheels and wanted to match it to my existing setup I basically want one magnet a hall switch and the relative setup to run 2 3" 7 segment displays as I will only be reading up to 88mph these are all powered by a 12vdc supply My magnet on my old setup is mounted to a 10" hub to which the wheel bolts too I've replicated the hall switch mount and magnet but my existing setup is sealed in a box with a silicone type rubber covering it so I'm loathed to scrape it all out just to see what components are inside If anyone knows what parts I need please let me know or I'll even buy a kit if someone can put it together

Kind regards Eddie

Get a Hall switch (the cheap Hall switches, linear Hall sensors cost more and are not what you need) and another magnet. Make sure you have the part number and manufacturer name so you can find the datasheet and example circuits.

Since in testing your wheel will be at constant speed (right?), only 1 magnet is enough.

Hi From 15 mph the wheel will be put under simulated extreme road force ( imagine a big roller on a hydraulic arm ) It will then be run up in 1mph increments to 88mph I've got the speed control worked out as I just copied what I have on my other rig but its the speed read out that I'm struggling with. I had the last one made because we used to use a laser rpm counter but it proved to unreliable with the deformation rate of the wheel and tyre I'll get the part number off the hall switch I bought tomorrow,was only a cheap ebay job to try,thinks its made by NGK Thanks for the response Eddie

Likely the (not much) worst case will be finding out how to point the thing at the magnet.

Have you ever used heat-shrink tube? It's a pro way to cover bare wire around solders but good for all kinds of seal-it-up uses. I mention it because of your silicon block potting of the other sensor.