12V diode tester

[adamrobot3456]

Hi,
I wish to create a diode tester using 12V SMPS and Arduino. I know how to measure such a characteristics using "traditional" methods:

but when measuring with Arduino it doesn't seem to be working properly (probably I'm doing sth wrong). If I pin it like shown on the schematic below:

I can easily measure voltage drop on a known resistor, so I can count current, however at that time I don't know how big is the diode voltage drop (when measuring voltage there it shows 0V, because it's connected to ground).

(Capacitors and 7812 are for stabilizing the supply voltage; potentiometer is 5k and is used to regulate voltage; voltage is measured via voltage divider R1=10k and R2 is 6.8k)

I know that my case might seems stupid to you, but I'm a beginner and I don't know how to measure it properly.
Thank you in advance for your comments!
Regards,
Adam

[6v6gt]

I would do the whole exercise first at 5 volts with just the diode and 100 Ohm resistor. That is assuming the diode is just a standard silicon diode (say 1N4007). Get that working with the Arduino and convert the analog values you read into a voltage. If you get that working, start building your 12 volt circuit. Be careful not to expose an Arduino pin to more than 5 volts.

[jim-p]

@adamrobot3456

but when measuring with Arduino it doesn't seem to be working properly

Explain by what you mean "not properly"
Is it always 0V, or always 5V of fluctuating up and down?

If you are using a 7812 then your input voltage MUST be greater than 14V

Please post your code

[TomGeorge]

Hi, @adamrobot3456

Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
That Fritzy image does not make it clear how you have connected your components.

You need to put bypass capacitors either side of the voltage regulator, look up the datasheet for the reg and it will show you.

Tom...

[johnerrington]

I dont read fritzys. Could you post a proper schematic please?

How to make a schematic you can post.

When you submit a question on the forum you will usually need to add a schematic (circuit diagram). The tutorial that follows will explain some ways to create a useful image; however lets start by explaining how to add the image to your post. Its easy. Having created the image all you need to do is : Save the image somewhere convenient - maybe your desktop Start your post, and place the cursor (insertion point) where you want the image to be shown; [upload image to forum] 3: click th…

Also you dont say what sort of diode you are testing. If its just a rectifier - like a 1n400x then unless you can apply a large reverse voltage the only char you will see ifs the forward characteristic - and you dnt need 12V - or even 5V - for that, as it is VERY unlikely with a working silicon diode to exceed 1V.
You can also test LED characteristics, you still dont need more than 5V.

[jim-p]

@adamrobot3456
I can read your wiring diagram.
No problem with what you posted.

[johnerrington]

Thanks Jim, I had another look. Fritzys are tricky for me because I'm color blind - in common with a LOT of the male population.

The fritzy shows the diode in forward conduction so I still dont see why 12V is needed.
Driving the circuit from the 5V supply via the 5k pot would eliminate the need for the divider networks , which will give better results.

[Wawa]

+1
My DMM has 3volt across the test leads on diode test, and diode current is 1mA.
A ~4k3 pull up resistor (not critical) between 5volt and the analogue pin would do the same.
The diode can then connect between pin and ground.
Measuring with 1.1volt Aref enabled will give you more A/D values to work with.
Leo..