Field Strength Sensor

[Maverick28]

Hi there i have a nifty project i found online that i want to have a crack at and understand and will need a little help!

1. I want to build a solenoid from electrical wire. I know how to do this, but just not to sure about how to meet the requirements of a solenoid. The solenoid must be capable of up to 2A of current. (how do i make this happen, i was thinking Iron nail with copper wire.)
2. Once i have built the solenoid i then want to mount a magnetic field strength sensor (Linear Hall Effect)
3. Then using OP amps i want to modify the output signal to provide 0-5V from the 0-2A from my solenoid.

Its pretty simple, but i just dont understand a few things, the circuit i have setup to modify my Vout2 is attached. Im pretty sure this is wrong so any help would be awesome!. V1 AND V2 are my hall effect sensor pins.

Thanks in Advance

 

[alec_t]

Will the solenoid be energised for long periods or just in brief pulses? You will need to choose your wire gauge accordingly (and depending on whether the solenoid is enclosed or open) to prevent over-heating.
What is the Hall device spec? Can you post a link to its datasheet?
You could probably use much higher resistor values than those shown if you are concerned about power consumption.

 

[Maverick28]

**broken link removed**

Heres our sensor, i got the solenoid working (there is a magnetic flield) and @ 2 amps it runs fine without getting hot. So i have a problem in my circuit now, the sensor doesn't seem to respond in general, so maybe im not facing it towards the right pole?. How do i determine the pole of the bolt? nether the less the how do i test my sensor to make sure it responds to my electromagnet?

 

[ericgibbs]

hi Maverick.
This pdf 'manual' gives an excellent introduction to Hall Effect devices.
E

 

[alec_t]

the sensor doesn't seem to respond in general, so maybe im not facing it towards the right pole?

In the presence of only the Earth's magnetic field the sensor output is typically 2.5V. It changes by only ~1.3mV per Gauss, so maybe that's not as much change as you're expecting? Depending whether your solenoid pole nearest the sensor is N or S the output will be 2.5V plus or minus some mV.

 

[tunedwolf]

The lines of the field run parallel to the length of the coil as I remember, so measuring it will require the sensor to be sited properly to be effective

I may be off course here, but given that you know the coil length, number of turns, coil diameter and the current through it can be accurately measured, would it not be simpler to just calculate the Gauss using Ampere's Law?

 

[jjw]

The resistor values R1-R4 are too low.
The output resistance of the sensor is about 200 ohm and you should use resistors at least 10 kohm.
What are v1 and v2 ?
Sensor has three pins: Vsupply, Gnd, Vout.