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How to use the ratiometric Hall effect sensor(UGN3503) in a levitron


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Hi
I want to build a levitron by using a PWM IC (UC3843). I explain the
PWM Controller behavior as below very simple to explain my problem.

PWM=1 if VFB < 2.5V (Controller Vref)
PWM=0 if VFB > 2.5V

In most of Levitrons on the web, The sensor is placed near the ElectroMagnet.
the ratiometric sensors output Voltage (Vout) is 2.5V when there is no magnetic field and Vout will Increase upto 4.2V or Decrease downto 1.2V depending on the magnetic field direction.
and this is what I can't understand:
When PWM is ON, the Vout (i.e.) will be 4.2V and absorb the levitron and Vout will Increase or decrease a little depending on the levitron magnet direction. if we add a Negative Offset voltage to Vout to bring it less down the controller Vref (2.5) to oblige the controller turn off, then when the electroMagnet turns off the Vout becomes a very low voltage and keep the Controller Off. (Vfb = Vout - Voffset)

maybe I couln't explain it very good, to understand my problem try to imagin the Sensor output voltage in different figures when it is close to electroMagnet and PWM turns ON and OFF .
Or In the link below, some one has opened a bought levitron device, can anyone explaine what happens to Sensors output when PWM is On and OFF

http://hi.ece.olin.edu/icb/spring_04/ttgb/student/Ukiyo/gallery.htm

ThanX in avance
Shahriar

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Hi Shahriar,

Why not buy one, they are not very expensive?
http://shop.conrad.se/cgi/websale6.cgi?Ctx=%7bver%2f6%2fver%7d%7bst%2f3eb%2fst%7d%7bcmd%2f0%2fcmd%7d%7bm%2fwebsale%2fm%7d%7bs%2fconrad%2dschweden%2fs%7d%7bl%2f01%2daa%2fl%7d%7bctx%2fffbcd3b2%2fctx%7d%7bmi%2f000355%2fmi%7d%7bpi%2f%2e%2e671157%2e%2e%2fpi%7d%7bpo%2f1%2fpo%7d%7btpl%2fhead%2ehtm%2ftpl%7d%7bsf%2f%3cs1%3esv%e4vande%20jordglob%3c%2fs1%3e%3cs2%3e%24%241%3c%2fs2%3e%2fsf%7d%7bmd5%2fb92489bd2b990446ddddfb1095826ede%2fmd5%7d

It’s less than 14€.

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Dear Ante
Would you mind just telling me the sensor output voltage in two condition (PWM=1 & PWM=0) if we assume the Distance between The sensor and Electromagnet is constant (just approximate numbers).
i.e If the distance is 2Cm the

Vout = ??? when PWM =1
Vout = ??? When PWM =0

Dear Audioguru
I don't think it is using such trick, the controller is just a Fan control.

ThanX
Shahriar

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Dear Ante
Would you mind just telling me the sensor output voltage in two condition (PWM=1 & PWM=0) if we assume the Distance between The sensor and Electromagnet is constant (just approximate numbers).
i.e If the distance is 2Cm the

Vout = ??? when PWM =1
Vout = ??? When PWM =0



That is impossible to answer, it depends on a lot of factors.
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