Hello all

I am attempting to make or buy a circuit for my needs but don't fully understand what i need if you see..

Basically i have a 12V Hall effect sensor in my gearbox, the output of the Hall switch sends a rectangular signal to the onboard computer. The frequency of this signal indicates the speed of the car.

The dash unit that displays the speed of the car is an 5v IR Optical sensor that is also on/off output.

How do i convert from the hall output to a usable on/off 5v?

Pics of the IR window circuit

Thanks!

 

Are you saying that the hall sensor in the gearbox is faulty and rather than replace it you want to simulate it's output signal from the optical sensor in the speedometer head ? Also are you sure that the hall sensor is on the gearbox output rather than it's input ?
Les.

 

Are you saying that the hall sensor in the gearbox is faulty and rather than replace it you want to simulate it's output signal from the optical sensor in the speedometer head ? Also are you sure that the hall sensor is on the gearbox output rather than it's input ?
Les.

Hi Les

No, the need for the conversion of the signal types has came from putting a newer engine in an older car.

The Hall sensor on the gearbox has a 12v feed, an earth and a signal wire. With my meter i can see a 0.5v output between the ground and signal wire, i have a scope on order but typically the output is a square wave from what i have seen in the past.

I have seen this on eBay, not sure if it will do the trick?

https://www.ebay.co.uk/itm/PWM-To-V...194304?hash=item5d76afd8c0:g:DXIAAOSwWeJbjKv-

 

With my meter i can see a 0.5v output between the ground and signal wire

0.5V seems very low. I would expect the Hall sensor output to switch between ground and 12V? Is your meter measuring some sort of average voltage? You really need a 'scope to check.
Would the pulse frequency from the Hall sensor be the same as from the optical sensor? I suspect not, if you're swapping engines, so you may need a pulse frequency multiplier/divider.
I don't see how that ebay item would be of use here.

 

Just so I understand better what yo are doing. Are you swapping just the engine or the engine and gearbox ?

Les.

 

Hi all
Conversion is already done, just need to give the ECU a speed signal and also get the digital dash reading.

I think i will await the scope and signal generator results and then go from there, will update as soon as i know.
Thanks everyone

 

Thats a Slotted Opto, not an Hall sensor.

A simple Npn transistor buffer running off a 5V supply fed from the Slotted Opto output will do that, easiest way to test is put a screwdriver or piece of paper between the gap in and out and measure the output on DC volts , you should get 0 to 12V .

 

Thats a Slotted Opto, not an Hall sensor.

A simple Npn transistor buffer running off a 5V supply fed from the Slotted Opto output will do that, easiest way to test is put a screwdriver or piece of paper between the gap in and out and measure the output on DC volts , you should get 0 to 12V .

That's the speedo dash clock end Dave, the gearbox hall sensor i will grab a pic of when the scope arrives

 

It may be that the hall sensor needs a pull-up resistor to deliver a better output. Try a 10K ohm resistor between the hall output and the +12 source and see if that gives a better signal. That is my good guess, it should not hurt anything if it is wrong.