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addy
10-12-2005, 01:20 AM
hi,
i am making a real time mine detector robo....
i need a very reliable circuit for detecting metals..
something which should respond with gud range and be reliable too......
plz don suggest any ckt using cs209a,tda etc. as they r not available in india.

venky
10-12-2005, 12:37 PM
hi u can use a pulse induction metal detector principle (its explained on protovale 's website just google for the firm website address i dont remember it)
essentially u need to have a pulse generator ( a 555 timer or any microcontroller with lookup tables/an internal sine wave generator can be used) these pulses are sent through an LC oscillator when a metal object comes in the oscillating magnetic field eddy currents generated increase the impedance and hence current level drops ....now u convert this current to a voltage (done by a simple resistor or even an op amp based circuit can be used) fed this voltage to a comparator when the reference voltage is suitably selected by u ( ths is hit and trial) then u can get an HIGH/LOW output that u can feed to a microcontroller ......
in case u have deep pockets buy TCA BG505 IC(from infineon/siemens) from rsindia.com they take 3 weeks for delivery & it costs 342 bucks....
in case u want to to draw u a circuit dia just mail me & in case of any query mail me...

vidur
10-13-2005, 06:34 AM
you can make a variable reactance oscillator

make a AF-LC oscillator using a fixed cap & a inductive search coil for sensing.....when it comes close to a metal....its frequency of oscillation changes...which you can obviously hear..

its the easiest concept....but have to do some math on the coils dimesions to fix the inductance

docel
10-13-2005, 09:09 AM
HI FOLKS!!
!. FM TX ANT AS METAL DET. 20 BUCKS FM RECEIVER DRIVES DIGGER MOTOR.
http://www.roboticsindia.com/modules.php?name=Forums&file=viewtopic&t=895&highlight=
I wonder if anyone read that....
Any oscillator will detune when close to 'Ground' objects. If you fool around with a Radio, you will see the effects of touching the antenna- the signal strength will decrease or increase.
The simplest method is to make a fm transmitter, say 100mHz. with a Loop antenna. A telescopic will also do. Off-tTune the fm receiver slightly. When the Tx antenna approaches metal or 'ground' it will be heard as a " strong' signal at the Rx. The speaker o/p can be routed to a Level det or window comparator for triggering some alarm etc,.

http://us.f1.yahoofs.com/groups/g_15856011/sah/FMTX.jpg?bcHthTDB_yXVkJNj

addy
12-17-2005, 04:57 PM
thanks....
ll give it a try

docel
12-27-2005, 04:19 PM
Did you?

tpsbpl
01-14-2007, 01:20 PM
i have a metal detector kit by gala electronics very prompt response and i am using it in my robot