I need to take a Hall Effect sensor and use it to control a relay in a 12 volt circuit. Needs to be weather resistant and tamper proof. Looking for ideas on the best way to go about it.
Thanks for any and all suggestions.
higgy

 

You state some conditions that suggest some intended placement -

Needs to be weather resistant and tamper proof.

Why is that? Where is that? What is the 12 volt circuit, and the load in amps?

 

Needs to be weather resistant and tamper proof.

You could put it in an outdoor safe.

Are you using this for a door sensor or security system?

 

I used to hid a 12 volt car battery In the woods to power experiments,or
just leave the battery so I would not have to handle It.You think you are
In the woods alone.The batteries always came up missing,If you leave
any thing of value It will be gone. Who take these things.

 

The idea is to use the signal generated by a vehicle speed sensor to limit the vehicles top speed by cutting the injectors power
I believe the injector circuit is 12v 30amp

 

Sounds dangerous, what would happen if you need to pass?

 

It is an off road vehicle with a federal mandate to not exceed 25mph
The idea is to use this type of circuit so that you have full power at anything below the 25mph restriction

 

The typical way to 'govern' vehicles speeds are to use the transmission. You know at which RPM in each gear that the vehicle reaches 25MPH. So you can use the hall effect sensor as a tach on the flywheel with an input from the transmission to restrict speed.

 

The hall effect sensor for the speedo is on the trans output shaft. I want to use the signal from this sensor to switch a relay for the injector driver circuit on and off at 25mph. Off above 25mph and on at anything below 25mph.Now I could remap the ecm to provide this function but I have neither the time nor the inclination to "crack" the current ecm code. So I am thinking I need some sort of amplifier for the Hall effects sensor to be able to switch a 12 volt relay installed in line with the power source for the injector driver but I have no idea how to go about this. If someone could point me in the proper direction I would appreciate it immensely. Thx
PS in the past this has been accomplished by welding restrictor plates on the trans to prevent 3rd and 4th gear operation. I think this is a silly idea and difficult to do on an automatic. Limiting speed with a relay for the injectors will work on either a manual or automatic and would allow normal engine and trans operation below 25mph. This would also eliminate the need for welding plates on every trans. Seems to me it would be a cheap add on regardless of vehicle setup.It will also have the added bonus of not affecting the engines emissions.

 

You can use an Op-amp to amplify the signal from the hall effect sensor, but you will most likely want to measure that signal with a uC and than have the uC trigger the relay. You can use a Darlington to get the amplification to energize the relay coil. It is dependent on the relay coil specs.

 

I understand op-amp and Darlington pair What is a uC?

 

Micro Controller

 

As in IC ? So once I find the output of the hall effect sensor at 25mph I can just find a suitable available chip and relay to do the job. I like that idea best. Thank you

 

One more question if I may
Do these hall effect IC's( two switches on a chip) have the power to switch a relay?

 

The hall effect sensor for the speedo is on the trans output shaft. I want to use the signal from this sensor to switch a relay for the injector driver circuit on and off at 25mph. Off above 25mph and on at anything below 25mph.

Does this hall effect sensor have an analog output proportional to the speed?

B. Morse

 

Yes,signal is proportional analog depending on the output shaft speed

 

Yes,signal is proportional analog depending on the output shaft speed

So you will need some sort of circuit that can be triggered at certain levels of output.... it looks like you will have to devise an comparator circuit that you can adjust a "high" and "low" trip points.... you can then use the output of the comparator to switch a transistor which in turn can switch a relay load....


My .02

B. Morse