hahaI had a quack doctor (Chiropractor) do a resistance test on my back. Where he pressed the probes hard then the computer showed a low measurement and he said I had a problem there. Where he pressed the probes lightly then the computer showed a high measurement and he said it was good there.
In the end he wanted $1500.00 to "fix" me.
I ran away.
couldn't you just use an ohm directly instead? If you are measuring in ohms.the average skin resistance of a healthy human is between 1.5 and 2.3M ohms. what this circuit does is when the person is lying their skin resistance goes down, which causes the current through the meter to go down.
I need more help understanding. And also I need to understand how the circuit works urgently. I need to understand how this circuit works in and out by Wednesday, this is urgent, please help. I am not very experienced with electronics, so please bare with me. I really need help.the reason it goes down is because Q1 is being opened further when the skin resistance goes down so less current is going through the ammeter. R2 is an adjusting resistor, and R1 is a current limiting resistor, maybe some of the other site members can do a better job at explaining than I can.
Thank you, but can you help me understand how the circuit works part by part also?Of course it "might" work. Some people sweat when they lie and other people sweat all the time, even when they tell the truth. Other people sweat only when they tell the truth because they usually lie all the time. Some people never sweat.
I am okay up until here, but when you say "current will stop to flow", do you mean through the capacitor?Dear your circuit is very simple and if u know about the working of capacitor and transistor then you can easily understand the working principle of this lie detector.but you should not worry because now I am going to explain the working of this circuit.As u know that in the circuit the voltage applied to the capacitor is 4.5v dc but the voltage applied to the transistor is 4.5+4.5=9v.you know that capacitor always block Dc voltage and there fore in this circuit initially when the capacitor is charged by the 4.5 dc then there will be flow of electrons from the negative terminal of the 4.5 dc and enters into the emitter of the transistor and go out from the base of the transistor and come to the one plate of the capacitor and in this way there will be accumulation of the electrons on one plate of the capacitor.In the same way from the other plate of the capacitor the electrons move towards the positive terminal of the 4.5 v dc and in this way there will be lack of negative charge or access of positive charge on the other plate.So in this way one plate has negative charge and second one has positive charge and therefore within few movements all the voltage equal to he 4.5 v will store in the capacitor and then current will stop to flow.
How does it help in the circuit when it discharges?now you must remember that after charging the capacitor has a 4.5 dc voltage across it so now if any kind of resistance is placed between the electrodes or terminals of wires then capacitor will try to discharge through that resistance with the voltage of 4.5v
Why no current? But doesn`t some current pass there before touching the collector?Dear you should remember that transistor only works in the condition if there is base current at the base of the transistor because transistor current (collector current) is controlled by the base current.if no body touches the electrodes then there will be no current at the base of the transistor and therefore the transistor will not passes the electrons coming from the down most supply.
Now I don't know who is right :-(Fayaz,
The capacitor at the input has nothing to do with the circuit. It is just a filter.
If there is no strong radio station or mains hum nearby then the circuit will work without the capacitor.