Hi.. i'm new to this site, but i have went thru many many pages looking for answers with no luck as of yet.. I have several questions i hope someone can answer. Here's what i have going on.. I'm making a meter that can detect and measure the stray ions that put off by a person, plant, animal, and can detect large concentrations of atmosphere ions. For the sensor, it's just a small metal plate surrounded by wood. I'm needing to inject the signal into a couple amplifier circuits so it can be read on a voltmeter.
So far i have it working, and i have about a 120mv swing from nothing to direct contact from my hand. And at this setting, i can measure people, water, fruits and other smaller things that put off energy, but electronics like phones, magnetism and anything inert doesn't register anything... and it's not supposed too.
Here's what i have so far.. i have a NPN transistor barely turned on and am injecting the sensor DC signal into the base with a biasing voltage so the transistor is barely turned on... so barely... that the sensor has to be plugged into the base before the transistor has enough voltage and current to turn on the transistor.. And i have a 555 timer with it set about 3.5 Mhz... Here's some the questions..
What happens to the 555 when there is no timing capacitor on the #6 threshold pin? i do have a capacitor on the #5 voltage control.. but without the #6 capacitor, i get a more of a reading from my sensor, and my voltmeter is still reads an AC signal throughout rest of the circuit. But when i install a cap on the #6, i still get a reading from my sensor... But it's only about half the reading as compared to no capacitor. i don't have access to an oscilloscope yet so i can't see what's going on.. And the output on the 555 is fed into the transistor collector.
I've also tried putting a small 1pf capacitor on the sensor going into the base of the NPN to make it an AC signal instead of DC.. and that works also... But i'm loosing sensitivity, and i can't seem to find any capacitors under 1pf.
Once i get this issue figured out.. I'm needing to amplify the signal more, either run it thru another couple transistors and/or possibly an op amp for voltage gain.
Any help or insight will help me greatly.. Thanks
So far i have it working, and i have about a 120mv swing from nothing to direct contact from my hand. And at this setting, i can measure people, water, fruits and other smaller things that put off energy, but electronics like phones, magnetism and anything inert doesn't register anything... and it's not supposed too.
Here's what i have so far.. i have a NPN transistor barely turned on and am injecting the sensor DC signal into the base with a biasing voltage so the transistor is barely turned on... so barely... that the sensor has to be plugged into the base before the transistor has enough voltage and current to turn on the transistor.. And i have a 555 timer with it set about 3.5 Mhz... Here's some the questions..
What happens to the 555 when there is no timing capacitor on the #6 threshold pin? i do have a capacitor on the #5 voltage control.. but without the #6 capacitor, i get a more of a reading from my sensor, and my voltmeter is still reads an AC signal throughout rest of the circuit. But when i install a cap on the #6, i still get a reading from my sensor... But it's only about half the reading as compared to no capacitor. i don't have access to an oscilloscope yet so i can't see what's going on.. And the output on the 555 is fed into the transistor collector.
I've also tried putting a small 1pf capacitor on the sensor going into the base of the NPN to make it an AC signal instead of DC.. and that works also... But i'm loosing sensitivity, and i can't seem to find any capacitors under 1pf.
Once i get this issue figured out.. I'm needing to amplify the signal more, either run it thru another couple transistors and/or possibly an op amp for voltage gain.
Any help or insight will help me greatly.. Thanks