hall effect signal on to 7seg display

Thread Starter

ralphh85

Joined Aug 29, 2007
3
hello im new here! hopefully someone on here can help me!

basically im tryign to bring up a number on a few 7 segment led displays dependent on the amount of pulses per min which come from a hall effect sensor.

i believe i will have to convert the hall effect signal to an analog dc voltage then put this in tot he LED display.

but where do i start? i have little electronics knowledge and dont have time to go back an do my A level!!

any ideas?


Ralph
 

beenthere

Joined Apr 20, 2004
15,819
You can get Hall effect sensors that have a digital output level. Apply the pulses to a counter chain, with a display showing the accumulated number.
 

Thread Starter

ralphh85

Joined Aug 29, 2007
3
well what im actually doing is...

i have an old metro which has real fast engine (143bhp vvc engine) and also a carPC. windows based small mini itx pc used for playing music mostly.

i want to remove my instrument cluster (speedo/rev counter/water temp/ etc etc) and replace it with a set of digi dials which i would really like to make myself as would be a good project!

the speedo sensor which i can put in (from a rover 200 or similar) is just a hall effect sensor and it gives out 4 pulses per revolution.

so i have the output i just need to bring it in and show up XXXmph.

i am totally open to ways of doing it with no restrictions, most of what was said/the pages i just viewed kinda went over my head!

whats the easiest way? i can wright basic software so must be able to pick it up somehow!


cheers for help
Ralph
 

Thread Starter

ralphh85

Joined Aug 29, 2007
3
i now know that obviously 0hz = 0mph

and not so obviously 120hz = 129mph!! on my car this may be closer to 120hz = 122mph due to different gearbox tho but i would like it to have adjustament anyway!



Ralph
 

kender

Joined Jan 17, 2007
264
You could use a panel meter. It’s an OEM device that takes an analog voltage and displays it on 7LED or LCD (depending on a model, of which there are hundreds).

Now, you need to convert pulses per minute to analog voltage. There are 2 possibilities:

- If the pulses have constant width, then the duty cycle is proportional to the frequency. Then you can simply low-pass filter pulsed signal to convert it to DC voltage level.
- If the pulses have a constant duty cycle, you could use a frequency to voltage converter (F/V). You can make one out of a 555 timer. Or you can get an F/V IC such as LM2917.

Of course, you can do all this with a microcontroller too.
 
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