It does sound good, but if it gets you no better results in mapping, costs 10 times as much, is trickier to build and involves sourcing some components that may not be available in the UK I'll stick with the one I've got.

 

Er, I was gonna build this cct but then I got high!

No really, where's the pics gone, I can't read and I need to follow the pretty pics. I went to the other page and now the cct looks different with added regulator (which I thought you didn't need).

Help.
Floyd

 

Sorry! Matt has just pointed out that the circuit has disappeared since secretlab went down. I will make it reappear tonight! Thanks.

 

Hurrah for John!

Ta
F

 

DONE

 

Eeeeee you chaps are great

Thanks to John Banks for the ideas, Scott.T for his circuit diagram (that I can understand and have followed for my board) and mutant_matt for his questions that enlightened me on a few points, and everyone else who has had input to this.

After three hours hard work, I've wired mine up and got the voltage on pin 4 to 690mV and pin 8 to 890 mV. Suffice to say I don't really understand electronics, but with the info you guys have given me, I've managed it (I think ). I've yet to wire the LEDs up, I'm using 5 discrete ones to monitor 810-890 mV, but I want to get a 220k pot first to be able to test it. The LEDs will be connected to wires, which will be wired along the top row of the board. Should allow me to fit them into my LED clips OK then

Here's a pic of my board (it may help to make some things clearer for people not electronically minded, like me )



Once my gauges arrive, I will be making a fascia plate to go where the centre column air vents are to house my three 52mm gauges, and the AFR LEDs down one side. I still can't believe how small this thing is (about 30mm x 40mm) and that I actually wired it up

Thanks again chaps, I'll hope to see you all on a meet sometime and compare handiwork D

Steve


[Edited by Hanslow - 3/2/2002 6:01:24 PM]

 

Top banana.

Seeing pictures of the inside of a Knocklink reveals it to be using the same chip and a few capacitors and diodes and an op amp. Should not be beyond someone to work out a design for that?

[Edited by john banks - 3/2/2002 6:06:30 PM]

 

Scott has used pins 1, 17, 15, 13, 11 (LED 1,3,5,7,9 on diagram below).



So you want a spread from 800mV to 900mV and they will light up at 810 830 850 870 890mV respectively.

[Edited by john banks - 3/2/2002 8:19:13 PM]

 

Aha, I see...didn't think you could fiddle it like that
That is indeed what I want to do, measure from 810mV->890mV.

I'll do that then and get fiddling with the POTs again.

As you probably guessed I got my pin numbering scheme mixed up trying to explain it , I went the wrong way round the chip, counting along the pins....duh!

Thanks a lot John


[Edited by Hanslow - 3/2/2002 8:27:58 PM]

 

Top, for easy retrieval.

 

Blimey, this drops quick here.

 

Mole

Never mind posting the pics Just pack in school and start earning a living building these things
I'll be your first customer, I'm fed up with my DVM kicking about in the passenger footwell !

cc

 

Just stumbled across this site on how to build an AFR guage that includes a voltage regulator in the circuit.

http://www.myzero.com/gauges/afgauge.html

 

Interesting page. However the lower reference is 0V, so for more accuracy the circuit would be best modified. Also the regulator is not required as the LM3914 contains good references already for power and the voltage reference.

 

Here's what you need to do, to make this circuit up using 5 LED's (Alot easier to produce than my 10 LED version)

Stripboard track cuts.....Viewed from compnent side



Stripboard is cut to approx 40mm x 40mm
BLACK DOTS - Signify Solder Joints
JOINED BLACK SQUARE - 2 Squares Joined by Solder
GREY SQUARES - Track Cuts
RED LINES/DOTS - Wire Links
GREEN CIRCLE THING - Potentiometers

Set LEDS to run from 820mv to 900mv

Fit all inside a small Black Plastic Box.

I can supply a full component list with Order numbers if required....

 

I hope to have details of Johns AFR up on my web site sometime during this week.

http://www.geocities.com/harryboy_scooby/

Scott, can I use your diagram to illustrate an alternative way of wiring in LED's instead of a 10 bar graph display?

Harry

 

HarryBoy,

No Problem, as long as I get a mention...

Cheers..

 

OK Scott

You got a deal!

Harry

 

CC,

But I need school to etch the boards! Doh!
Good idea though

Just got an e-mail back from Farnells, can't make an order under £10 For me with no money that's difficult!

I'll have to see about getting a box somewhere else.

If any of you are likely to order from Farnells give me a shout please! You could order me a box and I'll pay you etc.. etc..

Cheers, Richard

 

Right this is all a bit too techy for me but I want to have a go anyway, at least so I can play with a 9V battery setting it up and light up some lights

Please excuse my ignorance as I am not an electrical expert but I have one or two questions (which I don't think have been covered but I may be wrong).

I would like to do this but with individual LEDs a bit like HarryBoy has mentioned. Now, I've had a look at his website and at the bottom it says this :
The ECU is perfectly capable of looking after the mixture here so to get rid of the 'annoying Knight Rider' effect you can convert the AFR to use discrete LED's that are calibrated to light up only at 5% to 9% CO

Now I don't know how many LEDs I want to use yet, but I want to mount them on/in some plastic to give it a nice finish. I don't want to have it Knight Rider-ing on me all over the place distracting me whilst driving though. So, what would you need to do to stop it Knight Rider-ing when its running closed loop?

From HarryBoys quote, does only monitoring between 5% and 9% CO actually stop the Knight Rider effect? Is it just a case of adjusting the Pots to monitor a differnt voltage range, or is it a case of only wiring up certain pins/LEDs?

This may seem like an obvious/daft question, so I do apologise as I ain't electrically techy

 

If you set the references to 700 and 900mV you will turn on the LED1 at 720mV, LED2 at 740mV, LED3 at 760mV etc.

I have hooked up only LEDs 8,9 and 10 to get 5.5, 7 and 9% CO respectively at 850, 870 and 890mV. This avoids the Knight Rider effect. My references are 690 and 890mV.

This makes it suitable for use only above 10 PSI boost above 3000rpm on my car. This is the area I am interested in.

 

Thanks John, I'll give it a go (my first real venture into electronics )

 

I hear you are good with the greasy stuff. Electronics is easy - just wires and chip things really If a GP like myself can do it.... This particular circuit is quite difficult to blow yourself up with.

The only hazard really is shorts from unfused power supply (hence use a fused power supply), and connecting the lambda sensor to ground or 12V = dead lambda sensor.

Test is thoroughly before it goes on the car.

 

John,

Sorry to ask maybe what seems a daft question, but do you mean the of actual sensor wire (white) that's connected to the ECU of the lambda sensor & not the heater supply wires (red & black) when you say "connecting the lambda sensor to ground or 12V = dead lambda sensor"?

Regards

Johny.

 

Yes I mean the signal wire - if connected to 0 or 12V it would burn out the sensor.

 

John,

Figured I'd ask to confirm - much appreciated.

Johny.

 

Now I wouldn't call myself that handy with electronics but I'm going to give the AFR a go - got the kit ordered from a friend who has an account with RS, but never orders such parts.

Parts list (after a bit of research) - if anyone is interested for RS :

10-LED DIL - 246-5689
LM3914N - 308-174
4K7 lin pots - 187-012 (pack of 5)
PP3 battery clip - 489-021 (pack of 5 - have a few batteries)
RE520EP - 206-5857 (stripboard)

What I am wondering - I have read various remarks about the 4K7 pots, being trimmers etc. I just a have a few basic questions that will help me understand their function better.

1. My assumption is that a potentiometer/trimmer reduces a certain voltage to a lower voltage. This lower voltage being adjustable. Am I right with this?

2. Now people mention there are three pins - two bottom & one top. On looking at the circuit diagram & reading the posts - would you connect the original voltage to a bottom pin & ground to the other bottom pin. Would this give you the variable reduced voltage from the top pin?

3. Is the pot relative in it's reduction. i.e. If you connect a 9V battery & reduce the output voltage to say 1V. Then you connect a normal finger battery of 1.5V & then test & then a 12V & test again. I assume it's a relative reduction - ie. depending on the input voltage it'll be reduced by a certain say percentage. Am I near the mark?

Sorry about if the questions seem basic or even daft - but I can't even remember the last time I took a resistor in my hands nevermind a pot/trimmer.

Any help is better knowledge for me to tackle this so thanks in advance.

Regards

Johny


[Edited by jmca - 2/26/2002 10:21:18 AM]

 

A variable resistor is like a normal resistor except that there is a wiper that moves along a track and is the middle connection (with the arrow on circuit diagrams). It works as a proportional divider, and depending on the position, the voltage at the middle connection varies accordingly. So the variation is between either end and the middle connection. Try a google search on "variable resistor potential divider" and you might see some more?

 

hi, would anyone be willing to make me one of these afr meters as this small electronic stuff does not mean a thing to me! i printed off the original drawings etc, but still doesnt mean a thing.
obviously ill pay for the parts and the postage etc, and ill also pay extra for your time making it.

it would be much appreciated, as my car runs a bleed valve and i do not have a 4x4 rolling road near me, and do not have the time to travel to one, fact is i dont know whether my car is running too lean, so want some reassurance.

thanks

ian

 

You are best buying a Dawes AFR from performanceexhausts.net

This is a DIY design. I have no time to build them, although have had multiple requests. And there is no way I could make a profitable business out if it.

[Edited by john banks - 2/26/2002 4:40:48 PM]