ionisiation?

[Joes]

hi there

i have been making a control unit for gas/oil boiler i would like to try and get the ionisation probe to work with my aduino. i didnt know if anyone had tried this or has got any information on someting like this?

thanks

[robtillaart]

Can you share some pictures and/or code sofar (to get a better understanding of what you want to accomplish?

[Joes]

just found this link just a bit of general info about it. i havent gor any pics just a piece of ceramic with a metal bar going through it which is in the flame and th ceramic insulates it from the chassis
didnt know if anybody has played with this is the arduino world

http://www.petervis.com/electronics%20guides/polonium%20detector/ionisation%20chamber.html

[Grumpy_Mike]

Assuming you stick this in a flame, it will act as a conductor when it is in a flame and an insulator out of it.
So just put it between the input and ground and have an external pull up resistor of 1K.
It should work fine in a digital input.

[Joes]

ok cool
just to clarify where exactly should i put the resistor?

thanks

[Grumpy_Mike]

From the input pin to +5V.

[Joes]

ok thanks will have to have a play with that when i get time

[Joes]

hi again
i have made bit of a rig up and ran your theory above and i couldnt seem to get it to work at all. i think there is a bit more to it than i originally thought ?

[Grumpy_Mike]

A flame consists of ionized gas, if two conductors are placed in it then current will flow.
Many years ago I put an audio signal through a flame simply by placing it in series with the speaker connection.

If you are not getting anything from it try and measure the resistance of the probe and sheath, it might me made of some resistive materiel so that it works on a higher voltage.

[kunkmiester]

There will also be issues with the conductivity of the probe and flame, and your 1K resistor might be a bit much, if the probe's resistance is high enough.  Measure the resistance, and use Ohm's law to find the power drawn.  You want to make sure the power is below the max for the arduino, but high enough to register.  If the voltage is dropping too much to register, or the current is too high and tripping protection or something, it wouldn't work.

[MarkT]

Quick google suggests 100Mohms is a good starting point...  A flame is not that good a conductor!

Also found this fascinating page: http://www.sparkbangbuzz.com/flame-amp/flameamp.htm

[Joes]

hi there
i have been playing with different resistances. im up in the 2000k to get it to work on my test rig on my finished product i might be able to get it lower than that but i was wandering is it ok to use these sorts of resistances?

[Grumpy_Mike]

Well it won't do any harm but it might be a bit suceptable to noise.
You can try a higher voltage with a 5.1V zenner to protect the input.

[Joes]

what switch the live instead of the 0v?

[Grumpy_Mike]

Pardon?