Sensor circuit

[Red Fox]

I have a sensor that measures 2000 ohms in 1st position, 1400 ohms in second position. I would like to build a 12 volt D.C. circuit to control a relay.
12 volt power to relay coils in 2000 ohm position, relay contacts close,
Power to relay coils drop out, relay contacts open in 1400 ohm position.
The relay I an using has 220 ohms across the coil.
Any ideas appreciated.
Thanks
Red Fox

 

[Bluejets]

Depends on what the sensor is.
Can you elaborate?

 

[kellys_eye]

You want a voltage-dependent (sensing) switch.

The 'sensor' will form part of a resistive divider circuit who's output will be fed to the detector circuit that switches at the (pre)set voltage(s).

 

[WHONOES]

Easy enough using a comparator or even a single transistor + some other bits.

 

[Red Fox]

Depends on what the sensor is.
Can you elaborate?

It is a roll over sensor out of a Honda CBR 600 motorcycle.Honda part # 35161-MFJ-D02.It is connected to the onboard computer system of the bike. It is a mechanical pendulum sensor. Originally I tried using a inclinometer sensor part# SCA61T-FA1H1G-1 in a circuit . It works fine but vibration sets the chip off and triggers the relay. I figured this mechanical one in a motorcycle has vibration and if it worked in a motorcycle it should work for what I am using it for. I am using it for a sensor on a vertical plane(where there is vibration) and when the plane falls horizontal it would trigger the relay.
So I don't know how the computer in the motorcycle reads the sensor, but I figured someone out there is a lot smarter than me.

 

[Bluejets]

Perhaps try the above and if vibration is a problem you could " roll your own" with a magnet and a hall effect such as an Allegro A1120.
It is open collector output and will switch close to rail to rail.

 

[Red Fox]

Perhaps try the above and if vibration is a problem you could " roll your own" with a magnet and a hall effect such as an Allegro A1120.
It is open collector output and will switch close to rail to rail.

Thanks for the info, I will get some parts and see how it works.

 

[Red Fox]

OK, after much research and phone calls the Allegro A1120 will work with a south pole magnet against the chip,this will make the chip trip. I am using a round magnet in a tube to roll against the chip, some times the south side will be at the chip or sometimes it will be the north side against the chip or somewhere in between. So this idea will not work. Does anyone have a better idea?
Thanks

 

[Bluejets]

Yes......it's not the idea that will not work but your mechanical setup.
If the hall was mounted at the end of a brass tube and the magnet was mounted the end of a bolt for inertia the magnet would always approach the hall in the correct alignment.
If you want the magnet to arrive higgeldy piggeldy then perhaps a reed switch instead with a transistor amp.