Hi guys, I've got a data logger and timer. The timer is activated by push button, I want to change this for a hall effect switch to be triggered by a magnit. (40-50mm range). Has anyone got a simple circuit to do this??

Thanks

 

I'm not so familiar with Hall effect sensors or their sensitivity at that distance, but I'm guessing some signal amplification may be involved.

 

You will probably need to place the sensor at the input of a comparator, the comparator will then provide the TTL level or other output level required.

Actual circuit design requires determining the exact sensor to be used, the given magnet, and the distance between the two; along with the comparator details.

You may want to search on comparator application circuits.

 

Hi,

Put a reed relay in place of the switch. The magnet will close the contacts as long as it is near the reed.

 

Thanks guys, a reed switch is not senitive enough. Asfor circuit design, I dont know which sensor/comparator to use. Hence my visit to this forum!!

 

.............. a hall effect switch to be triggered by a magnit. (40-50mm range).

Have you found a sensor that will work at that range? Here is a site FAQ that indicates 4 to 6mm with the most powerful magnet is more likely.

http://www.allegromicro.com/faq/hedfaq1.htm

I'd start googling for sensor specifications first to see if you can find one that will work at that range.

What is the physical setup that is going to swing the magnet in front of the sensor?

 

I've worked with hall effect sensors several times, and I think it is difficult to get one to work at the range that you indicated. The range that Chris mentioned above is more likely.

If the distance can not be made nearer, then you probably could look at other type of sensors, like proximity or something else.

 

Thanks guys, the magnet can't be moved..... It's inbeded in the surface of the track that we race (Karts) on. The pickup is mounted on the kart, when the magnit is crossed it triggers the laptimer on the kart. Ok then if a hall effect is no good........... any other sugestions?

Dave

 

Kia Ora.
Doing a quick google shows the most common method is to use Transponders buried in the track.
http://www.chronelec.com/
Good luck.