geophone kit circuit reqest

[steven2]

ive found a simple looking geophone kit thats sold on the net but , i cant find any free circuits for it , they said they mounted it on a board and berried it under some dirt and it has leds on it and the closer it senses the footseps of people and even cats the more leds will light up, this circuit sounds simple but unlike other ones on the net that are technicle and use parts that even i cant get here, but the kit well from the picture it has only a few parts but im chaseing for the actual circuit schematics for that kit, or has anyone got a simpler circuit for one and allso  the details to make a geophone to, besides the circuit for it

 

[steven2]

here is a picture of the geophone circuit kit the metal thing on the left is the actual geophone

View attachment 38792

 

[steven2]

http://www.bgmicro.com/prodinfo.asp?sid=04652314814814816624966143&prodid=KIT1019&page=1&cri=KIT&stype=2

 

[steven2]

heres the latest ive been exsperimenting with an idea , first the inner section of the geophone , is a cylindrical cylender with a fine coil around it this cylender is suported by  sensitive springs , 2 at the top and 2 at the bottom  and through the cylender is a magnet now i beleave the soft highly springy springs that make the coil  on the cylender move up and down to the vibrations of the ground,  and the magnet inside that goes through it generate the tiny voltage and the circuit well it would need to detect this tiny voltage  and amplify it to a usefull level  heres what ive come up with , first i modified the circuit in my collection that i posted some time before , thats the circuit that allows ac to controll a dc relay , now ive left out the relay and put in a 3mm led and unknown diode 2b3 i think it has on it and then on the bread board i used some of the same parts to as the circuit has but i allso added some more and  i used the disc shaped coil from the microwave oven moters i pulled to bits and 3 powerfull rare earth magnets from pc hardrives  now i have a circuit that responds to the slight movement of the magnets above the coil , the led is allready lite briefly so the tiny movements of the magnet makes it go brighter or blink brighter , now if i hold the magnets stiffly above the coil and tap the top of my hand the vibrations and tiny jerky movement of my hand from being tapped makes the led react so easily , so now it would be easyer to have the coil , being lighter and easyer to vibrate, sitting above the magnet and suported by very sensitive springs to  so im getting some good results , now the led wont react to the powerfull ceramic magnets from microwave oven magnetrons so easy unlless you have ten of them but the powwerfull rare earth magnets sure do it easy for just 3 of them , ill post the circuit and details as soon as ive completed it all , ive allso added an extra transister to and parts  so i may end up haveing an easer version of ground vibration detecter  or  earth quake detecter to but the real test is when i can get and modify a coil to be very shock and vibration sensitive  to test for foot step detection  of which is what i hope it to do the magnets when held above the coil work when subjected to upward and downward vibrations of movements and not so much for side ways  unlless the round magnet stuck to the bottom of the 3 powerfull ones is protrudeing into  the coil, the magnets being heveyer than the coil would need more vibration to create a reaction so the coil would need to be  above the magnet in this approach , as i dont have any cylendrical rare earth magnets to go through the coil to use

 

[audioguru2]

Hi Steven,
Are you going to add an LM3914 or LM3915 bar-graph IC and 10 LEDs like in the kit you showed?

 

[steven2]

audio guru its just got one small led  and youll have to see the circuit to as you may want to make some corections  ill put it up soon, by the way i receaved email notification of reply to this topic but when i double clicked on it to get here i got a different page wanting details and password , is there some virus here wanting our login details , anyhow i shut it off and came here the other way

 

[steven2]

i welcome any modifications and changes  to this circuit, oh the 2 transisters are bc547b types  that transister is an improvement over the bc547 a types transister

View attachment 38810

 

[steven2]

View attachment 38811

 

[audioguru2]

Hi Steven,
In your circuit, the LED has nothing to limit its current and could easily burn out. The diode in series with it is doing nothing and should be changed to a 300 or 330 ohm resistor to limit the current to about 24mA.

Also, the 2nd transistor is doing nothing and should be removed since the 1st transistor is driving the LED.

Is the circuit sensitive enough?
It would be much more sensitive if the 1st transistor was designed to be an amplifier, instead of a switch. Now, it turns on when the signal from the coil exceeds 1.2V peak.

A BC547B isn't better than a BC547A. They have a different range of their wide current gain selected for you.

 

[steven2]

thankyou audio guru ive did some more exsperiments and used an lm386 audio amp circuit now ive got audio but ive allso  made a really sensitive one which works great ill add your changes  to it and post the others soon

 

[steven2]

here is the latest  pictures and circuits , the first one is the 7141 inverting or non inverting op amp circuit i added to the lm386 audio amp and with the microwave oven coil in place this one makes audio nioses to the movement of the powerfull rare eath magnets held above it  but this one still aint as sensitive as i want it

View attachment 38815

 

[steven2]

this next circuit is just the 741 inverting op amp or non inverting op amp circuit with a few samll changes made to it as for the small led , well i had a 1k current limiting resister for it but changed it to 390 ohms then i ended up settleing for the 2.2k as each test with each resister resulted in top performance and sensitivity  with the 2.2k current limiting resister for the led, as if its made the whole circuit more sensitive , and the tiny led although is lite it responds to the tinyest movement of the rare earth magnets  and it dose it good to  the led intensity changes are easy to see and the more the vibrating movements of the magnet the more it will react , i can just barely hold the magnets still enougth to  stop the led from reacting thats how sensitive it is , and with a tiny camera lense peace it will be easyer to notice the led intensity changes like its flickering and even on and off to the movements of the magnet

 

[audioguru2]

Hi Steven,
A 741 opamp won't work properly with its non-inverting input pin 3 connected to the negative supply voltage. Pin 3 should be biased to a voltage that is half the supply voltage with a voltage divider made with two series resistors. Then pin 3 should have a bypass capacitor to the negative supply.

An opamp won't work properly with its inverting input's input resistor connected through the coil to the negative supply voltage. It should have a coupling capacitor.

The output of the 741 opamp is supposed to have a DC voltage on it. Since your circuit has pin 3 of the LM386 amp directly connected to it then the LM386 will amplify that DC voltage and not work properly. A coupling capacitor should feed its pin 3.

The 104 (0.1uF) capacitor at pin 3 to ground of the LM386 is an AC dead short to ground to the output of the 741 opamp and might cause it to oscillate at a high frequency. If the capacitor is used as a high frequency filter then it should have a resistor freeding it from the 741.

I didn't see you opamp driving an LED circuit.

 

[steven2]

View attachment 38816

 

[steven2]

ill work on it more then but the latest picture here works perfect to and the led responds incredibly easy to the most tinyest movements of the magnets  as for the 104 monoblock in the other with the lm386 op amp well i used the same circuit  as did with the super snooper type circuit i think it was yours oe staigens idea to use the 104 so i used it from the pin to ground

 

[steven2]

the 741 inverting or non inverting amp circuit i got that off the net i just added the coil to it and led and current limiting resister, and as for the first circuit well its the circuit that allows ac to controll dc i just modified it so the  dc led comes on from the induced ac into the coil from the magnet , ill take out the diode and second tranny to as recamended by you audio guru

 

[steven2]

here is a picture of what the actual geophone looks like inside so ill have to do some constrution here to get the coil as bouncy as possible to be sensitive

View attachment 38817

 

[steven2]

i couldent find the right picture but this will do

 

[audioguru2]

as for the 104 monoblock in the other with the lm386 op amp well i used the same circuit