I am still debating if the arduino will be beneficial in what I want to accomplish and was hoping on some support to lean me to the correct path. This is for a science fair project.
The project is going to have conductive and non conductive materials, 5 in total, and I will need to show the voltage and current, if any, of the material on a display screen. The setup I was looking for is as follows.
When I power the project up using a 6v or 9th battery the following happens. First, the first material is selected and an led light is turned on to show this selection, if the material is conductive, it will display the voltage and current going through the material, if it is not conductive it will show zero or null. The project will then automatically switch to the next material and do the same thing. It will turn the led indicator on showing the new selection then display voltage and current if any. It will do this for all materials with an eight second delay between each material selection. Then, the cycle keeps repeating until the battery dies or system is turned off.
is this something that can be accomplished with the arduino or am I stuck using 2 dmm to show the voltage and current and manually selecting each material?
You can measure both current and voltage provided that the voltage is less than 5V, and you can measure current by passing it through a resistor of a know (low) value and measure voltage across the resistor.
I think (no doubt others will correct me) that if you connect the test piece as part of a voltage divider and measure the voltage at the junction you will be able to calculate the resistance of the sample - and hence the current through it
Robin2's suggestion allows you to output a voltage and current output from one analogue input which has a certain elegance to it. It leaves a lot of other pins to do something else... You can of course then connect 6 samples, (and on some boards more).
Thank you all for the feedback. Looks like I will purchasing the arduino.
As far as displaying the info and making it cycle automatically, Wil this be done by programming? Also, what would be the best kit for this project.
Would it be technically easier to just keep voltage at 5v and just calculate the current going through an object, but still display both voltage and current read outs.
Sorry for all the questions. I am not versed in electronics but I want to learn and at the same time show my child how to apply it using the science project as our base.
Ah. For the aluminium and copper they will have to be very thing and long in order to notice a practical difference. Aluminium has a lower resistance by weight, copper much lower by volume. (Which is why underground cables are copper and pylon wires are steel cored aluminium).
Well I would swap the sample and resistor over to make the maths easier and to actually be measuring the current.
You will not see any difference in metals though as the absoloute resistance will be too low.
How about using some of that Bare conducting paint with various lengths of track?
It is not much admittedly but you measure the voltage across the resistor and so you are directly measuring the current. In my mind the maths of that is easier to calculate / visualise. But it is no biggie.
Grumpy_Mike:
It is not much admittedly but you measure the voltage across the resistor and so you are directly measuring the current. In my mind the maths of that is easier to calculate / visualise. But it is no biggie.
If the metal wire is sufficiently thin and very long you may see a difference... but I have not seen aluminium wire available... but then I have not looked for it either!