mods - please don't shunt this off into computer related too quickly

i'm thinking of adding a lambda sensor to my car to help monitor and setup the carbs. i guess i can get any heated lambda sensor and weld it into the exhaust manifold. from what i can gather they will produce different amounts of resistance depending on the gas analysis (i would need to know the specific details for the lambda sensor in question).

now, you can buy LED type guages from demon tweeks etc that will indicate if the mixture is lean, etc. what i was thinking of doing is buying/building an interface board that could attach to the serial port of a laptop. i could then write a program to communicate with the RS232 serial port and using the lambda sensors data i could print out the relevant information in realtime via a nice GUI.

so - does anyone know where i can start looking to gather info on communicating with an RS232 port (i've seen the RS232 standards etc) and all the software can be done easily enough but i'm clueless when it comes to the hardware (well, i know how it works in theory) side of things (obviously i need some hardware to convert voltages/resistance values into an RS232 compatible signal).

cheers,
steven

 

I think there's a guy called PCB on here may be able to help you on this.
I think he has something to do with the SECS system.

 

just seen this : http://www.students.tut.fi/~eppu/dev/EGO-bar.html

exactly what demon tweeks etc sell for ~£100. i could build one of these very cheaply but still like the idea of linking up to the pc

 

If your interested in teh AFR Meter see :-

http://www.scoobynet.co.uk/bbs/threa...ThreadID=57428

 

this is even better - http://www.autospeed.com/cms/article.html?&A=0217

but once again just an LED output. really want to get the voltage ouptut .1-.7 volts to a serial (RS232 port) so i can display the results on the pc

 

IanW - that link is brilliant

just need someone to tell me how to link this to the PC!

 

Sounds like a job for a pic chip to me.

Sensor to the ADC on the pic, and have the pic write the value out through a MAX232. Or use the pic to drive a LCD to display the info.

Something i've thought of doing but not got round to yet - i'm thinking of doing a digital dash disply for the car i'm building.

John

 

john - that means nothing to me but i'll go research what you said.

yeah, because once i figure out how to get this to display on the PC i will be able to monitor other sensors (very fast and furious).

i will build the standard LED type first and get that working well then get this linked up to a laptop

 

another query - anyone know where i can buy a lambda sensor (heated 3 wire one) and how much they cost? i guess they all put out the same voltages at AF ratios?

another good link

http://www.buckeyetriumphs.org/technical/Carbs/AFMonitor/AFMonitor.htm

[Edited by midget1500 - 4/27/2003 8:56:53 PM]

 

£30ish for a 3 wire from Eurocarparts but, for tuning purposes you are better off with a wide band probe. I don't know where to get these at sensible prices ATM

 

If you're thinking about pic chips, have a look at www.microchip.com (manuf's web site). Also, Everyday Practical Electronics mag has recently started running a tutorial, part 2 is in the mag that's in newsies at the moment.

I had a play with them a few months ago, but nothing serious yet.

John

 

ok - built the unit using 0-1 volt scale (for initial testing). all the lights came on under full throttle!! (this is in a 2000 1.3 fiesta). hooked up a DVM to the lambda and went for a drive and got the following...

max 1.076v
min 0.034v
avg 0.549v

under WOT it sat around 1.038 which means the car would be running stupidly rich (and is >1 volt?!?!) which blows away all the voltage v. AFR scales i have seen.

so, anyone know where you can get a voltage v. AFR chart from for a particular lambda sensor (i.e. manufacturer? surely they wouldn't give one out? or do you get one with a new sensor?)

steven - confused

 

If you want to do it properly get a DIY Oz Wideband. This has a display, RS232 output and logging software. Far more accurate than a wideband.

http://www.techedge.com.au/vehicle/wbo2/default.htm

I believe that narrowband lambda sensors have an ECU controlled heater usually. This may be for cold start to get it up to operating temperature, but also I know they get damaged if they are unpowered, so there might be more to it.

However, narrowband is lame away from 14.7:1 which even on a NA engine is well away from peak power, so strongly suggest get the wideband.

 

john - thanks for that link. looks like the next step - just wish this other thing had of worked for now...