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Solving stress meter, IC LM3915 and touch pad

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Kaian277

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to magnatro

thnx for the link but im still confuse how it works but base on the datasheet non are related to my stress meter curcuit...i did construct it on the breadboard but when i test it its not working properly :S.......
 

magnatro

New Member
it's not a circuit that you need to head bang, it's really a simple logarithmic display having a simple preamp for boosting the input signal that's all!!
 
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Reloadron

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thnx for the link but im still confuse how it works but base on the datasheet non are related to my stress meter curcuit...i did construct it on the breadboard but when i test it its not working properly :S.......
Attached is your schematic so others can easily view it.

First as was mentioned I suggest you study the data sheets for the LM3915 and the LM3914 wouldn't hurt either. That chip is the heart of the circuit. Note the examples of using the chips in the data sheets.

The sensor in your circuit is no more than two wires that are bridged by a finger tip. Note where the sensor is placed and what bridging it with a finger tip will do? How about a moist finger tip? A dry finger tip? The text body explains the theory of operation a little. Try to understand what T1 does with its associated components.

Ron
 

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Kaian277

New Member
hey sorry i was soo busy lately anyway my circuit on the breadboard was a success the reason it wasnt success was the resistor 47Kohm it was too strong for my circuit so i replace it with a 47kOhm trimmer/potentiometer and it works perfectly

the touch pad i use alluminnium coil as reloudron suggested using moist hand it coducts it very well

now im on transferring it to my PCB anyway wish me luck :)
 

pratyusha

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hi iam pratyusha...i want to know weather i can replace touch pads with any component...please help me sir
 
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cowboybob

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hi iam pratyusha...i want to know weather i can replace touch pads with any component...please help me sir
Yes, you could, but for what purpose?

The basic circuit is essentially a conductivity sensor, i.e., the "Touch Pads" have a bias across them and your finger provides a current path.

Any component placed across the pad locations will affect the circuit response, obviously, but it will give you a response both predictable and, in my opinion, of no practical value.
 

pratyusha

New Member
thank u.but for me touch pads are not available so i thought of replacing that with another component.is it possible?and also i want to about the usage of switch in stress meter will u please help me
 

cowboybob

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Most Helpful Member
I see what you're asking.

The touch "pads" can be made from any conductor; for instance, they could be two bare wires, or two metal squares (circles) made from an aluminum can, etc..

... also i want to about the usage of switch in stress meter ...
What do you want the switch to control (there's already an "On/Off" switch)?
 
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