(word processor parameters LM=8, RM=75, TM=2, BM=2) Taken from KeelyNet BBS (214) 324-3501 Sponsored by Vangard Sciences PO BOX 1031 Mesquite, TX 75150 There are ABSOLUTELY NO RESTRICTIONS on duplicating, publishing or distributing the files on KeelyNet except where noted! May 16, 1993 MAGCHECK.ASC -------------------------------------------------------------------- This file shared with KeelyNet courtesy of Mark Mansfield. -------------------------------------------------------------------- Anyone need a way to check magnetic fields? Well here's a circuit that will allow you to do just that! It is simple, low cost, and if calibrated can be very accurate. It will distinguish between north and south poles. It does this by outputing a voltage ABOVE 1/2 supply voltage for north poles and outputing a voltage BELOW 1/2 supply voltage for south poles. This causes the meter to either swing above center zero for north poles and below zero for south poles. The Hall effect sensor has a side that is the measure side and as long as you have it toward the magnet it will tell you which pole it is and its relative strength. If you want to calibrate the instrument for gauss field reading, you will have to come up with either a calibrated magnet or build you a circuit to do the calibration. That's beyond the scope of this paper. If you need such a circuit, let me know and I'll send you a copy of it. The construction is straight forward and does not require a circuit board. Just use point-to-point wiring. Anyone with electronics background should have no problems building it. I mounted my sensor on a piece of 2 conductor shielded wire about 3 feet long. This allows me to move the sensor around freely. I mounted the components is a small aluminum box. I used a small wall transformer to supply the power for the circuit although it could be battery powered just as easily. No big tricks or surprises in this circuit. Just simple and works! Page 1 + 12V | DC _|_ | | 1000 | | ohm + 12Volts DC |___| res. | | ___|_____ CAL. Pot. _ _|_ | Hall | ______ / \ | | | Effect | _______| 10K |_________/ \________>| | 200 | Sensor | | |______| \ / |___| ohm |__________| | ^ \ _ / | pot. | |_______| _|_ | 50 uA | | 1000 ///// Meter | | ohm zero center |___| res. UGN3501U | SEE NOTE | BELOW | ///// SPECIAL NOTE: The value of the bottom 1000 ohm resistor may have to be changed slightly from the 1000 ohms. I had to add 200 ohms to it so my zero control was in its center position when the meter was in the center position. Parts List: (1) UGN3501U Hall Effect sensor (Available from Newark Electronics) (1) 10K ohm pot. for calibration (1) 200 ohm panel mount pot. for meter zeroing (2) 1000 ohm 1% metal film resistors, 1/4 watt (1) 50 microamp meter, preferably zero center (1) regulated 12 Volt DC power source, 50 mA or more. Note: If you have trouble finding the Hall Effect sensor, drop me a note and I'll try to help you out. Have fun!!!! Mark Mansfield -------------------------------------------------------------------- If you have comments or other information relating to such topics as this paper covers, please upload to KeelyNet or send to the Vangard Sciences address as listed on the first page. Thank you for your consideration, interest and support. Jerry W. Decker.........Ron Barker...........Chuck Henderson Vangard Sciences/KeelyNet -------------------------------------------------------------------- If we can be of service, you may contact Jerry at (214) 324-8741 or Ron at (214) 242-9346 -------------------------------------------------------------------- Page 2