Register Login
The UK's No.1 Chrysler Owners Forum
Comment
 
Guide Tools
<!-- google_ad_section_start -->How to produce a lambda sensor tester by yourself<!-- google_ad_section_end -->
How to produce a lambda sensor tester by yourself
Published by andre79ge
10-04-2005
Unrated

User Rated:Unrated

Show Printable Version  Email this Page 
How to produce a lambda sensor tester by yourself

Basically, Fiat Uno lambda sensor produces a variable voltage in the range 0 - 1 V (in some cars there is another type of Lambda which produces 0 - 5 V voltage).
When mixture is correct, tension is about 0.5V, if it is lower, it means a poor mixture, if it is higher, it means rich mixture.
ECU reads this signal and corrects the fuel injection for correct carburation.

In order to check this voltage you can use a voltmeter.
But... this voltage moves from 0 to 1 (and reverse) 2 or 3 times every second. From the other side, a normal digital tester (a DVM) has a display time refresh more longer (for example 1 second). The consequence is that you photograph your lambda on every second and this is not very useful. Y'd need to photograph its excursion, and this means that you' d need a time refresh approx of 0.1 seconds (so you can appreciate voltages excursions during their develop).

I present an electronical stuff which permits to photograph this tension continuatively.
It is basically based on LM 3914 chip.
This chip contains all you need. You have to connect it only to some leds (which will light one after other as soon as lambda voltage will grow up), and two resistors. Then you also have to provide it with the 12 V of the car.

On national.com website you can download the datasheet for this chip, go to this www address and push on "download" for the pdf data sheet:
http://www.national.com/pf/LM/LM3914.html

I developed the circuit present on the second page of the pdf.
That layout permits to see 0 led lightning if input tension is 0V;
Provides 10 led lightning if input tension is 5V.
But Uno lambda develops only 0.8 or 0.9 V at top, so you have to put another resistor in circuit: if you watch to the formula in the datasheet, you 'll understand that the correct value is R2=0 ohms. Basically, you don't put any resistor in R2, you will only put R1 with the value of the sheet.
Then you have a voltmeter that lights on all leds with 1.25 input voltage (a little more of your max lambda voltage).

Then you connect the input pin of the chip with the output of lambda.
What you have to see on led?
When engine is cold you have to see some led ON (the first 2 or 3), because lambda is cold (no active output) and ECU goes in open loop.
As soon as it warms up, lambda starts to launch signals and ECU starts to correct injection up and down.
Then you have to see leds to light and stop from 0 led on to 7-8 led on, at minimum 1 time every second.

Where you can find lambda voltage?
You have to see on your outlet mainfold: quite near engine head you will clearly see your lambda sensor (a metal cylinder with a cable which exits from it) put inside the mainfold and screwed inside.
You have to "follow" (not sure of this word) the cable (i mean watch the cable and analyze its run inside the engine compartment). It will go in the compartment, and on the left side (if you are in front of the car) you will see that this cable has a connector, connected with another cable.
(This connector is useful if there is the need to change lambda: you unscrew it and disconnect old lambda).
There is 1 connector or more probably 2 dependently by your car.
If there are 2 connectors, identify the brown cable (the 2 white are for warming up lambda and you are not interested in them), uncover it (there is an easy rubber big cover at the terminal which permits to cover/uncover it without any damage) and there connect the pin of IC.
The ground connection is provided by the chassis of the car (so you MUST connect IC power V+ pin to the +12V of the car, and connect the GROUND POINT of your IC to the chassis of the car. I used the "cigarettes fire" inside the car).

The better way is to provide a long cable from lambda connection to the inside of your car, where you will place your circuit.
Then try to go on road: when you push gas, you have to see leds light and not light alternatively.
If you relase accelerator, with engine more than approx 2000 rpm, you have to see all leds OFF: infact ECU cuts completely injection if you relase accelerator at warmed up.

If you can't develop the circuit,
you can use a normal digital tester.
Put the voltage scale to 2 V, put the black terminal to the ground (battery "-" pin), and put the red cable to the labda voltage pin.
Then you have to read a constant value at cold (approx 0.4 0.5V) and you have to see fluctuate that value when warmed up. But it's not as precise as the other circuit!

Let me know if it's not clear!
I'm not familiar with English.
Cheers!
Andrea.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

Old 10-04-2005   #1
Panda 100K+ club
 
Louie Bee's Avatar
Join Date: Oct 2004
Location: N.W.
Posts: 2,846
Thanks: 84
Trader Rating: 9
Louie Bee has donated!
Rollin X Pinball Champion, Bubble Bobble Champion
Mozambique 
Thumbs up Re: How to produce a lambda sensor tester by yourself

Many Thanks for the Post Andrea!

I will be building one soon…

… LOL - If I ever get off my computer

Your English is Good! Clear to me! With a brilliant link. This thread must have taken a long time to type up. More rep coming your way

Kind Regards,
__________________
Louie Bee is offline Reply With Quote Quote 
Old 10-04-2005   #2
Join Date: Apr 2005
Location: Athens
Posts: 53
Thanks: 0
Trader Rating: 0
Greece 
Re: How to produce a lambda sensor tester by yourself

Thanks a lot for the info, i am downloading it now and i will try it
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

geom is offline Reply With Quote Quote 
Old 12-04-2005   #3
Join Date: Oct 2004
Posts: 63
Thanks: 2
Trader Rating: 0
Italy 
Good!

Ok!
I have something for you.
Try to test your apparatus before to put it in the car: you can use a simple 1.5V battery and generate a voltage between 0 to 1.5 V with a variable resistor.
Use a variable of approx 1 Kohm, and put its ending pins to + and - of the 1,5 battery.
Then give power to your lambda tester (tipically 12 V) and connect its ground to the - of the 1,5 battery.
Then connect the floating of the variable to the INPIT pin of the IC. Rotating the resistor (and so varying it output voltage) you have to see leds to turn ON or OFF.
Note that you 'd prefer a linear variable: a log variable will cause all led (or almost none) to light with a little rotation of resistor (because its resistance change is not linear but it has a logarithmical shape).

However I'm very interested in your lambda output in order to check it with mine!!
Cheers!
Andre.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

andre79ge is offline Reply With Quote Quote 
Old 12-04-2005   #4
Join Date: Nov 2003
Location: Newcastle - upon - Tyne
Posts: 2,587
Thanks: 1
Trader Rating: 0
polecat has donated!
United Kingdom 
Re: Good!

Excellent post Andre. Rep gained.
polecat is offline Reply With Quote Quote 
Old 12-04-2005   #5
Panda 100K+ club
 
Louie Bee's Avatar
Join Date: Oct 2004
Location: N.W.
Posts: 2,846
Thanks: 84
Trader Rating: 9
Louie Bee has donated!
Rollin X Pinball Champion, Bubble Bobble Champion
Mozambique 
Re: How to produce a lambda sensor tester by yourself

I also think it would be a good idea to try your electronics project well away from the car!

Oh - If only I had of kept and fixed that old Cathode ray oscilloscope, I could have given the readings.

Hmm I recall a computer program, which utilises sound card inputs, to a turn the PC into a C.R.O. Would be useful for laptop owners. I can’t remember the name off the top of my head, but you could save print out the results. – Ill let you know If I remember.

Then again, one could use the Line In inputs and a simple audio record program, once the audio Db scale has been calibrated. LOL I’m not recommending anyone tries – if it goes wrong any blows up your laptop – don’t blame me.

LOL - rep already awarded (for first post).
__________________

Last edited by Louie Bee; 12-04-2005 at 21:49. Reason: rep
Louie Bee is offline Reply With Quote Quote 
Old 12-04-2005   #6
Join Date: Aug 2004
Posts: 391
Thanks: 0
Trader Rating: 1
ohit has donated!
United Kingdom 
Re: How to produce a lambda sensor tester by yourself

That's brilliant! Very interesting. I'd love to try it, but my Uno doesn't have a lambda.
__________________
156 JTD
ohit is offline Reply With Quote Quote 
Old 16-04-2005   #7
Join Date: Oct 2004
Posts: 63
Thanks: 2
Trader Rating: 0
Italy 
Re: How to produce a lambda sensor tester by yourself

Hello!
Are you proceeding in building up the tester? ^_^
I' m so courious!!!
Andre.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

andre79ge is offline Reply With Quote Quote 
Old 16-04-2005   #8
Panda 100K+ club
 
Louie Bee's Avatar
Join Date: Oct 2004
Location: N.W.
Posts: 2,846
Thanks: 84
Trader Rating: 9
Louie Bee has donated!
Rollin X Pinball Champion, Bubble Bobble Champion
Mozambique 
Re: How to produce a lambda sensor tester by yourself

Hi Andre,

(As I said in my e-mail), unfortunately I won’t be building mine for some time, as I will be concentrating on my new MK1 Uno with no Cat converter.

Hopefully, I will build one in the coming months and post Photographs of the process.

Do you have any pictures if the device?

Just ask if you need help uploading them

Kind Regards,
__________________
Louie Bee is offline Reply With Quote Quote 
Old 17-04-2005   #9
Join Date: Oct 2004
Posts: 63
Thanks: 2
Trader Rating: 0
Italy 
Re: How to produce a lambda sensor tester by yourself

Sorry, I did not read your last email! I'll read it soon.
I'll try to produce some pictures of the object!
Cheers,
Andre.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

andre79ge is offline Reply With Quote Quote 
Old 28-04-2005   #10
Join Date: Sep 2004
Posts: 220
Thanks: 0
Trader Rating: 0
Malta 
Re: How to produce a lambda sensor tester by yourself

Thanks alot dude.

I wanted to ask, is this a kind of A/F meter?

On a punto mk2 8v do you know what is the voltage (0v-1v or 0v-5v)?

And I believe it is the upward lambda sensor that I need not the one ofter the cat right?
__________________
--- Punto mk2 8v---
*Int & Ext neons**Tinting**Int Alum trim**Momo gear set**Momo pedal set*
*Body graphics**Custom Ice install**Custom A'Pex Integration CAI**Sports exhaust**Racing Seat Belts**Removed seats**Lexan Windows**Weight reduction*
Neo-The Matrix is offline Reply With Quote Quote 
Old 28-04-2005   #11
Join Date: Apr 2005
Location: Athens
Posts: 53
Thanks: 0
Trader Rating: 0
Greece 
Re: Good!

Unfortunately i didnt find this LM3914 yet
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides

geom is offline Reply With Quote Quote 
Old 28-04-2005   #12
Panda 100K+ club
 
Louie Bee's Avatar
Join Date: Oct 2004
Location: N.W.
Posts: 2,846
Thanks: 84
Trader Rating: 9
Louie Bee has donated!
Rollin X Pinball Champion, Bubble Bobble Champion
Mozambique 
Re: How to produce a lambda sensor tester by yourself

Quote Originally Posted by Neo-The Matrix
...I wanted to ask, is this a kind of A/F meter?

On a punto mk2 8v do you know what is the voltage (0v-1v or 0v-5v)?

And I believe it is the upward lambda sensor that I need not the one ofter the cat right?
A/F = Audio Frequency right the changing voltage as suggested
Quote Originally Posted by andre79ge
“this voltage moves from 0 to 1 (and reverse) 2 or 3 times every second
would be 2 – 3 Hz. thats so too slow for audio frequency (20 – 20Khz). Depending on the shape of the wave, there may well be harmonics in the audio frequency domain (Furrier analysis).

Not sure about the Punto TBH. The Uno has 1 lambada sensor before the cat.
__________________
Louie Bee is offline Reply With Quote Quote 
Old 28-04-2005   #13
Join Date: Apr 2005
Location: Athens
Posts: 53
Thanks: 0
Trader Rating: 0
Greece 
Re: How to produce a lambda sensor tester by yourself

I think A/F means AIR FUEL ratio (except audio frequency)
This circuit acts like an Air Fuel meter, if i correctly understood the datasheet and the circuit diagrams.
__________________
FIAT Forum Useful Links:
Donate to FF | Buy FF Merchandise | Classifieds | FF Insurance | How-to Guides


Last edited by geom; 28-04-2005 at 16:44.
geom is offline Reply With Quote Quote 
Old 28-04-2005   #14
Panda 100K+ club
 
Louie Bee's Avatar
Join Date: Oct 2004
Location: N.W.
Posts: 2,846
Thanks: 84
Trader Rating: 9
Louie Bee has donated!
Rollin X Pinball Champion, Bubble Bobble Champion
Mozambique 
Red face Af



Silly me again.
__________________
Louie Bee is offline Reply With Quote Quote 
Comment
Currently Active Users Viewing This Guide: 1 (0 members and 1 guests)
 
Guide Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump
Similar Threads
Guide Guide Starter Category Comments Last Post
(T) Punto 55s -97 lambda problem? ice0018 Punto (Mk1) 7 06-06-2007 11:14
(T) New Lambda same problem shadders_SX Punto (Mk2/2b) 4 23-01-2005 18:55
Fiat Bravo 100 SX Lambda Sensor Problem Scrumpy Lets Talk FIAT 9 21-12-2004 16:48
(T) Lambda sensor and MPG dan4natz Cinquecento / Seicento 3 12-11-2004 20:09
(T) RPM & Lambda Sensor (Coupe 16V Turbo) CYL Coupe 1 09-11-2004 22:33