Arduino Forum

Using Arduino => General Electronics => Topic started by: cloxart on May 19, 2018, 05:58 pm

Title: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 05:58 pm
Hello everybody,
I do have a temperature sensor that i am trying to integrate in a project. The device was supposed to be an infrared temperature sensor, but when i opened it up to try to understand how to get a useful signal out of it I only found a small PCB with a LASER diode (TOSHIBA TOLD 9200) pointing at the lens. I understand that the laser beam is used as an aid in aiming the sensor at the correct spot for temperature reading, and since there are no other components pointing at the lens, I can only guess that the tiny signal from the photodiode inside the laser diode is used to get a reading (obviously after turning the laser off). this is supported by the presence of an OP AMP (AD760). I have drawn up the circuit board and I am attaching pictures of the original board and my drawings (one of them with transparent components so you can see where the tracks are going underneath them). I have ZERO experience with SMD components, I managed to understand that the black ones (marked 1002) should be resistors and the glass orange one a diode. the other components (gray ones) are they capacitors?? there are no marks on them. and the black one with three pins marked A7p what is it?? (only 2 pins of it are connected) I tried to search the net but had no luck. there are 5 wires coming out of the device: yellow, white/red, green, red, black.
Is there anyone who can help me make sense of that? (I am ready to pay for that if needed)

Kind regards
Title: Re: simple circuit reverse engineering
Post by: PaulRB on May 19, 2018, 06:12 pm
(https://forum.arduino.cc/index.php?action=dlattach;topic=548383.0;attach=258428)
(https://forum.arduino.cc/index.php?action=dlattach;topic=548383.0;attach=258430)
(https://forum.arduino.cc/index.php?action=dlattach;topic=548383.0;attach=258432)
Title: Re: simple circuit reverse engineering
Post by: jremington on May 19, 2018, 06:17 pm
You have not explained what you actually want to do, but to attempt to reverse engineer a device like that, as a novice, is not a good way to start any project.

If you want to use an Arduino compatible infrared, non contact temperature sensor, I suggest to get the MLX90614 (https://learn.adafruit.com/using-melexis-mlx90614-non-contact-sensors/wiring-and-test) individual sensor, or the Grid Eye 8x8 thermal camera (https://learn.adafruit.com/adafruit-amg8833-8x8-thermal-camera-sensor/overview).

If you carefully follow just about any of the many tutorials on line, they will work right away.
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 06:25 pm
Hello jremington,
thanks for your reply. What I am doing is an automatinc welding machine. In order to know when to start the welding process I need to know when the part reaches the set temperature. The reason I need to use that particular sensor is that I have 5 of them available, taken from old welding machines and doing that exact job of sensing the welding temperature. I am by no means a "novice" with arduino and programming, but i can only define myself an "hobbyist" regarding electronic, and I never ever used SMD components, that is why I am asking for help.
Title: Re: simple circuit reverse engineering
Post by: jremington on May 19, 2018, 06:32 pm
You are definitely a novice with reverse engineering.

Good luck with your project!
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 06:42 pm
Thank you again jremington for your post,
but if all you have to say are derogatory comments I would suggest that you dont waste your time on that.

Regards
Title: Re: simple circuit reverse engineering
Post by: jremington on May 19, 2018, 06:49 pm
There is nothing "derogatory" about being a novice. Everyone has to start somewhere!
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 06:52 pm
I still think your comments are not adding anything to this forum, and not offering any help..., just wasting space and time.
Title: Re: simple circuit reverse engineering
Post by: Paul_KD7HB on May 19, 2018, 07:10 pm
Get a box of colored pencils.

With a regular lead pencil, draw a box on a sheet of paper for each and every component on the board. Label the boxes with the id of each component it represents.

Pick one box and with a colored pencil draw all the connections from that component to every other component. Lay that color aside.

Pick another color and begin to draw the connections for another box.

When all done, draw a proper schematic using standard symbols. All connections needed for the schematic should be apparent from your colored pencil drawing. Where multiple colored lines connect components, you know only a single board trace connects them all.

Paul
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 07:15 pm
Thank you Paul,
that is what i did to obtain the drawings I posted... but i still do not know if the gray/brown parts are capacitors or what... and what A7p is, I was hoping for some help in identifying those parts.
Title: Re: simple circuit reverse engineering
Post by: Paul_KD7HB on May 19, 2018, 07:16 pm
Thank you Paul,
that is what i did to obtain the drawings I posted... but i still do not know if the gray/brown parts are capacitors or what... and what A7p is, I was hoping for some help in identifying those parts.
Did you try your ohmmeter?

Paul
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 07:25 pm
yes
Did you try your ohmmeter?

Paul
Yes, and the black ones looks indeed resistors (marked 1002 and reading indeed 10Kohms) the gray parts all read as no conduction but one, which reads 22Kohms so I take that's a resistor, which would make sense as it is the one connected to the non inverting input of the op amp. still struggling with the A7p... 3 pins so at first look i thought it was a transistor, but only TWO pins of it are connected.
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 07:49 pm
I can only make sense of the circuit if I assume that A7p is a diode. I indeed sketched up the circuit in a simulator and it is working if I apply 12V to yellow and 5V on red, GND on green and I take black as output.
in that way I can get an output on the black wire depending on the voltage (0~20mV) I apply on on the feedback pin of the laser diode. Still no clue about the red/white wire. (the original equipment is connected through a shielded cable, and the red/white is connected to the outer mesh of the cable, but NOT to ground)
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 08:06 pm
A7p - on the bottom of the page

http://radioskot.ru/forum/9-449-27 (http://radioskot.ru/forum/9-449-27)
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 08:10 pm
Thanks Ted! so it IS a diode! :)
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 08:18 pm
https://www.master-laptop.com/pages/articles-mesin-bga-services-17/marking-code-component-51.html (https://www.master-laptop.com/pages/articles-mesin-bga-services-17/marking-code-component-51.html)
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 08:20 pm
single
http://etronics.free.fr/dossiers/analog/analog10/images/image28.gif (http://etronics.free.fr/dossiers/analog/analog10/images/image28.gif)
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 08:26 pm
Thanks Ted, that really helps
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 08:29 pm
More problems ?
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 08:35 pm
Oh yes! lol
still dont know what the red/white wire is for, for instance.
in the simulator i put a generic op amp (the only choice I have) but the AD706 in my circuit is a DUAL op amp so I guess it must be powered with a dual voltage.... and not as I did
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 08:38 pm
dual = 2 op amp in one package
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 08:40 pm
opps, sorry I meant BIPOLAR
http://www.analog.com/media/en/technical-documentation/data-sheets/AD706.pdf
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 08:46 pm
Op amp can work in two modes or single mode of power supply.
google - dual supply op amp circuit and single supply
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 08:49 pm
here is the schematics i was able to make
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 08:49 pm
post # 1 top drawing, which wire is red and which white ?
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 08:54 pm
from top to bottom:

left side:

yellow
white/red
green
red

on the right side:
black
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 09:18 pm
I sent you a PM Ted :)
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 10:18 pm
From top
IN - to control laser beam
OUT - signal from photodiode
+ voltage supply
- voltage supply
Black
control bias op amp
The circuit is using only one op amp.
Double check your drawing - op amp is in strange configuration
Title: Re: simple circuit reverse engineering
Post by: ted on May 19, 2018, 10:32 pm
google - ir thermometer circuit

https://www.google.ca/search?q=ir+thermometer+circuit&rlz=1C1NCHB_en&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiPxdD5zpLbAhVJ_IMKHfJDAd8Q_AUICigB&biw=1440&bih=784 (https://www.google.ca/search?q=ir+thermometer+circuit&rlz=1C1NCHB_en&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiPxdD5zpLbAhVJ_IMKHfJDAd8Q_AUICigB&biw=1440&bih=784)
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 19, 2018, 10:40 pm
great! but red wire is going straight into pin8 (v+) of the ic?? and green into pin1 (v-)... is there something i dont get? obviously there is :(
Title: Re: simple circuit reverse engineering
Post by: ted on May 20, 2018, 12:00 am
For double op amp is almost standard - pin #4 is ground or minus and #8 is +, the easiest way to find out  where you connect the battery
Title: Re: simple circuit reverse engineering
Post by: ted on May 20, 2018, 12:17 am
(http://circuits.datasheetdir.com/37/AD706-pinout.jpg)
Title: Re: simple circuit reverse engineering
Post by: ted on May 20, 2018, 05:22 am
Double check your drawing - op amp is in strange configuration
I did not notice that the op amp is upside down.

Correction
IN - to control laser beam
IN - photodiode modulation signal
Signal Out - from photodiode
Red + voltage supply
Black - voltage supply
Title: Re: simple circuit reverse engineering
Post by: TomGeorge on May 20, 2018, 01:11 pm
The reason I need to use that particular sensor is that I have 5 of them available, taken from old welding machines and doing that exact job of sensing the welding temperature.
How were they integrated into the old welding machines?
Tom.. :)
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 20, 2018, 01:55 pm
@Ted: you say black = -V, but black is going into OUT1??

@ TomGeorge: I have no way to check, they were originally mounted on some induction welding machines (CEIA LOGE 23) but the machines has gone and the manufacturer that I contacted said they do not have any documentations as it is a very old model.
Title: Re: simple circuit reverse engineering
Post by: ted on May 20, 2018, 02:13 pm
correction of correction

Title: Re: simple circuit reverse engineering
Post by: ted on May 20, 2018, 02:14 pm
(http://forum.arduino.cc/index.php?action=dlattach;topic=548383.0;attach=258651)
Title: Re: simple circuit reverse engineering
Post by: cloxart on May 20, 2018, 02:30 pm
thanks Ted,
I guess I should start testing it... do you think I am correct in assuming that on the laser beam wire I must connect a current limited supply?
Title: Re: simple circuit reverse engineering
Post by: ted on May 20, 2018, 02:42 pm
All LEDs required current limit, the simplest is a resistor - 200 -300 ohm .
That is 3V laser diode.

LED wire (brown ) - required modulation signal,

google - chopper amplifier