Pages: [1]   Go Down
 Author Topic: Uno, signal conditioning and an optical sensor  (Read 1152 times) 0 Members and 1 Guest are viewing this topic.
Offline
Newbie
Karma: 1
Posts: 42
 « on: September 20, 2012, 01:32:39 pm » Bigger Smaller Reset

Hello, I am new to both Arduino and electronics.  I have an Uno R3 and the need to use a SICK NT6 optical sensor to recognise changing greyscale.  The documentation uses the expression "Analog output QA: 0.15 mA ... 6 mA" - the "QA" of which I have Googled to no avail.

I've tried to figure out how (using umpteen different tutorials) to view the problem of connecting this satisfactorily to the Uno but am at a loss.

This is what I think I know:

The Uno can take between 0V and 5V at up to 40mA.
The SICK is permitted to use anything from 10V and 30V DC to power it.
I've tested the SICK in a scenario where I showed it black and then white and using a digital multimeter the output varied between roughly 0.6V and 1.6V (I thought that I had seen a larger Voltage range in a spec somewhere).

I would be grateful for a structured approach to how I should properly pull this problem apart.

Many thanks.

 Logged

Switzerland
Offline
Karma: 108
Posts: 5144
 « Reply #1 on: September 20, 2012, 01:52:25 pm » Bigger Smaller Reset

The product description I found on the internet says analog output on QA is 0.15...6V, so a simple voltage divider (2 resistors) to an analog input should do the job.
 Logged

Illinois, USA
Offline
Full Member
Karma: 0
Posts: 124
 « Reply #2 on: September 20, 2012, 01:56:48 pm » Bigger Smaller Reset

V = I * R it's not just a good idea, it the law. Ohm's Law.

You don't even need a divider. A 200 ohm resistor to ground will convert the current to a voltage from 0.03 to 3.2V.
 Logged

Offline
Newbie
Karma: 1
Posts: 42
 « Reply #3 on: September 20, 2012, 02:10:24 pm » Bigger Smaller Reset

The product description I found on the internet says analog output on QA is 0.15...6V, so a simple voltage divider (2 resistors) to an analog input should do the job.

Pylon, how does this relate to the current reference that I found (" 0.15 mA ... 6 mA")...and how does that fit into the picture...  What does QA mean?

Thanks
 Logged

Illinois, USA
Offline
Full Member
Karma: 0
Posts: 124
 « Reply #4 on: September 20, 2012, 02:12:45 pm » Bigger Smaller Reset

QA probably means the pin. Often in electronics outputs are labeled 'Qx' (Qa, Qb, Qc etc.)
 Logged

Offline
Newbie
Karma: 1
Posts: 42
 « Reply #5 on: September 20, 2012, 02:22:17 pm » Bigger Smaller Reset

QA probably means the pin. Often in electronics outputs are labeled 'Qx' (Qa, Qb, Qc etc.)

Thanks Karma.  I'll take a look at the feedback and have a play.  Have to say I'm nervous about my reference being Current and Pylons being Volt (!)
 « Last Edit: September 20, 2012, 02:39:37 pm by 2Tricky » Logged

Switzerland
Offline
Karma: 108
Posts: 5144
 « Reply #6 on: September 21, 2012, 04:08:17 am » Bigger Smaller Reset

My reference document is from here: https://mysick.com/saqqara/im0007888.pdf, where is your's?

There is only an output voltage (nothing about current output), so if in doubt I'd use the voltage divider.
 Logged

Offline
Newbie
Karma: 1
Posts: 42
 « Reply #7 on: September 23, 2012, 03:44:24 pm » Bigger Smaller Reset

My reference document is from here: https://mysick.com/saqqara/im0007888.pdf, where is your's?

There is only an output voltage (nothing about current output), so if in doubt I'd use the voltage divider.

Here's mine: https://www.mysick.com/eCat.aspx?go=FinderSearch&Cat=Gus&At=Fa&Cult=English&FamilyID=376&List=1&Category=Produktfinder&Selections=42939

Is this likely to be OR can it be correct given that your reference states Volts...

I've been trying to measure the analogue outputs to no avail but am wondering whether the cheap transformer I'm using (and lack of knowledge) could be leading me astray. The multimeter shows this 12V unit giving out 18V and I'm wondering whether its not very smooth.  If the Sick does vary current in line with different greyscale values detected, what is the implication?

A few hours later: Have spoken to Sick and it is being verified.

Result: Sick confirmed spec should give voltage not current.

Thanks.
 « Last Edit: September 24, 2012, 11:23:24 am by 2Tricky » Logged

 Pages: [1]   Go Up