thanks ron! i seem to be getting a reading by just blowing on the sensor without having any alcohol in my system(not even vapor in my mouth). would you have any idea as to what could be causing this?
mr513 hotwire alcohol gas sniffer interface to arduino
-
24th November 2011 12:40 PM #11Reloadron
The data sheet does leave a little to be desired. They do show a bottom view pinout with Compensation and Detector labeled. The charts also show the expected outputs for gas concentrations. Here is what I suggest you do. Provide a 3 volt or so excitation and measure the output voltage. Try subjecting the sensor to gas concentrations. This is sort of hit/skip short of having standard concentrations. See what the output voltage does. This should give you an idea as to if you will or will not need amplification. The charts show an output of about 400 mV for a 1200 ppm (Parts Per Million) concentration. That would lead me to opt for some amplification.
The sensor is a complete little bridge circuit. You provide the excitation of 3 volts and it outputs a millivolt signal proportional to the gas concentration it senses (sniffs).
The analog input pins are 0 to 5 volts to a 10 bit A/D and thus 0 to 5 volts in = 0 to 1023 or 1023 A/D quantization levels.
Ron+1Please do not PM me with forum related questions. Let's keep things in the open forum. Thank you.
-
3rd December 2011 04:08 AM Thread Starter #12tommowas
0
-
3rd December 2011 05:51 AM Thread Starter #13tommowas
also would you know the wiring for the c and d nodes? i have this setup c to capacitor to vcc, c2 to d1 to analogue input, d2 to ground not working out really well for me... any help would be appreciated. i have tried different combinations with no luck..
cheers0
-
4th December 2011 01:07 AM #14Reloadron
Hi Ya
Your bridge should look like the attached image. The M513 sensor is the two nodes. You are adding 3 resistors total using two each of 2 K Ohm and a 500 ohm potentiometer. You are applying an excitation voltage not to exceed 3.1 volts maximum. When you start getting above 3.0 volts the bridge will have a self heating effect. Resistors R1 and R2 which are 2 K Ohm resistors should be 1% resistors. Well as closely matched as possible anyway. Resistor R3 is used to balance the bridge (the zero).
According to the data sheet it looks like a concentration of about 1,000 PPM should output about 400 mV while 0 PPM is 0 mV. With 0 PPM you would use the 500 Ohm pot to adjust for zero out. If there is drift (excessive) drift on the output at zero then the bridge excitation voltage is is too high. The normal bridge current should be about 100 mA +/- 10 mA.
Now are you setup like the attached drawing? I would get this much working first measuring the output using a DMM. Then I would worry about maybe some amplification to drive the Arduino but first get the bridge working and balanced.
Ron+1Please do not PM me with forum related questions. Let's keep things in the open forum. Thank you.
-
4th December 2011 04:24 AM Thread Starter #15tommowas
hey ron
this is how i have it setup, attached is a bottom view pic of the sensor with d & c pins divided up and marked.
c1 goes to 20ohm resistor then to the 5v power rail. d2 goes to ground, c2 & d1 goto analogue inputs. the difference of c2 and d1 is the result. i cannot get a reading though.. is there anychance i could of blown the circuit of the wheatstone bridge?
also when i was getting a reading i was getting a reading with alcohol present and without alcohol present. scratching my head for hours..
cheers0
-
4th December 2011 09:49 AM #16Reloadron
Measure using an ohmmeter across C1 & C2 then D1 & D2. You should get approximately 2 K Ohm across each. That will tell us if the elements are still good.
As to the module itself:
The two elements are placed into a Wheatstone Bridge configuration as I show in the drawing I posted. The resistance of the D (Detection) element will change in the presence of alcohol atmosphere. That change causes a bridge imbalance resulting in an output voltage signal from the bridge. The compensation element is only for compensation. Any temperature change felt by D will be compensated for by C. You need to add the additional 2 K resistors shown as R1 and R2 in my drawing. Based on what you posted there is a good possibility the elements are toasted from excessive current. Measure the resistance across the D and C elements as I suggest and see what you get.MR513 consists detecting
element and compensation element, both elements are placed in a wheatstone bridge
circuit, when the alcohol concentration appears, the detecting element resistor reduces,
bridge circuit voltage output changes, the voltage will increase according to the alcohol
concentration increase, the compensation element refers to temperature compensation
affection.
Ron0Please do not PM me with forum related questions. Let's keep things in the open forum. Thank you.
| Tags |
| Similar Threads | ||||
| Thread | Starter | Forum | Replies | Last Post |
| Interface Labview and arduino | trojan89 | Electronic Projects Design/Ideas/Reviews | 0 | 16th October 2010, 12:57 PM |
| subscriber line interface IC needed | waqar | Datasheets, Manuals or Parts | 1 | 19th April 2004, 07:23 PM |
| SENSOR:nemoto resistive semiconductor alcohol sensor(INDIA) | Anish | Datasheets, Manuals or Parts | 1 | 24th June 2003, 02:52 PM |
| Digital Panel Meter Interface | mark43 | Electronic Projects Design/Ideas/Reviews | 7 | 29th March 2003, 08:16 AM |
| Building an Alcohol Level Indicator Ckt. | sumitkaul | Electronic Projects Design/Ideas/Reviews | 1 | 14th July 2002, 06:18 AM |