Ion detector

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Your question depends a great deal on the type of ions you want to detect and the conditions. For example, are you talking about detecting detecting ions in free air or in a closed system of inert gas or vacuum?

John
 
I would like to detect the negative ions produced by a ionizer... It should tell me weather any negative ion is produced.
 
Have you tried searching under: negative ion detector? I got more than four pages of hits that included several commercial as well as DIY devices. Here's just one **broken link removed**.

John
 

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According to the example... how do i convert it to digital mode? i would like to display it on a LCD if possible.
 
It would have been nice to know you wanted something digital and presented on an LCD earlier on.

Now, what exactly is it you would like to quantitate and in what units? John
 
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connect it to a PIC and display it out using LCD ? what do u mean by what units ? according to the example.. it is (mA)....i have no idea how to make it digital
 
Current (mA) through a resistor is converted to volts. Replace the meter with a resistor, feed the voltage across the resistor to ground and the PIC's ADC input pin, have the PIC read the voltage and do it's thing. The 9V battery should be isolated from the +5v and Ground on the PIC. Also, diode protect the PIC's input from <0v and >+5v inputs from the FET circuit.

Ken
 
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"The 9V battery should be isolated from the +5v and Ground on the PIC. Also, diode protect the PIC's input from <0v and >+5v inputs from the FET circuit."

what do u mean by this? how to isolate the 9V battery from +5V and ground of the PIC..
 
The 9v battery is attached as shown in jpanhalt's circuit. The PIC's -5v(ground/common) is attached to the pot's wiper and the Pic's ADC input is attached to the FET drain. There are no "direct" connections between +9v, -9v, +5v, and -5V...that's the "isolation" part. You will need separate switches to turn the 9v and 5v supplies on and off...one DPST switch. For input protection of the PIC, I would place a 1OK resistor between the drain of the FET and the input of the PIC's ADC. And one a diode (cathode) from the +5v to the PIC ADC (anode) and a second diode (anode) from the -5v to the PIC ADC (cathode).

And in fact you don't even need to replace the meter with a resistor, just drop th meter. The meter is really acting as a voltmeter, measuring the voltage difference between the pot wiper and the FET drain/2.2k resistor connection. That's what your PIC will do.

Ken
 
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Did you read the article link "example" in jpanhalt's post?

Since you PIC will not read negative voltages as the "zero center" meter would, the pot will set the zero ions input to your PIC at +2.5v.

Ken
 
+2.5 V?... when there is no static charge or negative ions detected, the voltage i get from my DMM is -4V to +1V .. varies when i change the value of the pot. so.. what value should the pot set to..? 0V ?
 
You should set the pot (multimeter -) to a value at the FET drain (multimeter +) of +2.5V, with no ions's detected. That will allow th PIC to see the "negative" readings as +2.5V to 0V, and the "positive" reading s as +2.5v to +5V. The programming can scale these voltages to whatever you want.

Ken
 
i attached the ADC pin to the FET drain and ground to the pot. .... voltage out of the multimeter is -2 to 5.....(varying with the change of the POT) i donno what value of the pot should be set ....

the LCD displayed the voltage o the ADC pin is 255 with 5V supplpied to it...(cant go any higher)..why ?
 
As I said..."You should set the pot (multimeter -) to a value at the FET drain (multimeter +) of +2.5V, with no ions detected."

+2.5v will give be the zero ion level to the PIC...128 out of the ADC. The maximum negative ion level will be <+5.0...255 out of the ADC. The maximum positive ion level will be >+0.0...0 out of the ADC.

As far as the "0" on the LCD with +5v (255) into the PIC, I can't help you. This will require someone knowledgeable with your PIC, programming, and LCD.

Ken
 
Hi, I am so out of electronics these days hope someone will be patient with me and can possibly help an old man? I have seen the cct that jpanhalt has referred to with a center zeroed meter, which I am having enormous problems trying to source at the moment. perhaps I am looking on the incorrect type of sites, however my main question is, are there amy other ccts with more readily available components and something that could be used with leds to show the presence of negative or positive readings? I need something for my application of the instrument that can be seen if neccessary in pitch black TIA
 
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