DIY AFR meter for £10 with excellent results!
05 December 2001, 03:36 PM
#33
Scooby Regular
Join Date: Jun 2001
Posts: 160
Likes: 0
Received 0 Likes
on
0 Posts
John,
correct, we don't need to regulate the supply voltage. The ref. voltage is derived internally. Also checked my unit (still not fitted it!) and the 700/900mV points remain constant at 5v or 9v supply.
Harry
correct, we don't need to regulate the supply voltage. The ref. voltage is derived internally. Also checked my unit (still not fitted it!) and the 700/900mV points remain constant at 5v or 9v supply.
Harry
05 December 2001, 03:58 PM
#35
Scooby Regular
Join Date: Jan 2001
Location: Powered by "SOLARIS"
Posts: 1,694
Likes: 0
Received 0 Likes
on
0 Posts
Apart from regulating the supply it will take any 'noise' out of the supply ( I am assuming people will power from tha car. (you are right though if input range is that wide then regulation is not needed)
---john---
---john---
05 December 2001, 05:22 PM
#37
Scooby Regular
Thread Starter
Join Date: Nov 2000
Location: 32 cylinders and many cats
Posts: 18,658
Likes: 0
Received 1 Like
on
1 Post
I was thinking the same, along with boost, outside temperate, oil temp.
Have been looking every where for a Knock display. Will read your link with great interest.
I know my knock sensor gives a steady 2.43V at idle and changes a little when you put the A/C on, but other than that still to fiddle.
Have been looking every where for a Knock display. Will read your link with great interest.
I know my knock sensor gives a steady 2.43V at idle and changes a little when you put the A/C on, but other than that still to fiddle.
05 December 2001, 05:35 PM
#38
Scooby Regular
Thread Starter
Join Date: Nov 2000
Location: 32 cylinders and many cats
Posts: 18,658
Likes: 0
Received 1 Like
on
1 Post
As far as I have been able to find Scott I cannot see in our cars a line that is pulled low when knock is detected like this circuit is designed for.
Since it is a microphone, how about linking one of the AFR devices we have made and looking at what voltages it gives off - presumably it will flicker a bit more at high revs. Could then work out what is normal and adjust accordingly. Would love to see what is inside a Knock Link
Since it is a microphone, how about linking one of the AFR devices we have made and looking at what voltages it gives off - presumably it will flicker a bit more at high revs. Could then work out what is normal and adjust accordingly. Would love to see what is inside a Knock Link
06 December 2001, 08:54 AM
#40
Scooby Regular
Join Date: Jun 2001
Posts: 160
Likes: 0
Received 0 Likes
on
0 Posts
I finally fitted the AFR last night and went for a gentle run around-the-block, seems to be working OK.
One funny thing I noticed is at idle the LED's light up then go out IE: it's like the night rider affect. Not all light up just the first (720mv) up to the eight (860mv) in sequence.
It does this every 2-3 seconds or so, up the scale then down again. John did yours do this?
Harry
One funny thing I noticed is at idle the LED's light up then go out IE: it's like the night rider affect. Not all light up just the first (720mv) up to the eight (860mv) in sequence.
It does this every 2-3 seconds or so, up the scale then down again. John did yours do this?
Harry
06 December 2001, 09:10 AM
#41
Scooby Regular
Join Date: Jun 2001
Posts: 160
Likes: 0
Received 0 Likes
on
0 Posts
I think this has been said before but no harm in repeating it.
I picked up the Lamda feed from the ECU connector B136 PIN 21 as John did. It's the first connector facing you (lower)and was coloured Blue on my UK MY00. I used one of those blue Scotchlok connectors.
The pin connection detailed in the PossumLink V5 manual on Page 33 shows B136 viewed as looking into the plug from the connector side not the loom/wire side so you need to pick up the wire from the opposite side when the plug is turned around. My wire was white with silver dots.
Harry
I picked up the Lamda feed from the ECU connector B136 PIN 21 as John did. It's the first connector facing you (lower)and was coloured Blue on my UK MY00. I used one of those blue Scotchlok connectors.
The pin connection detailed in the PossumLink V5 manual on Page 33 shows B136 viewed as looking into the plug from the connector side not the loom/wire side so you need to pick up the wire from the opposite side when the plug is turned around. My wire was white with silver dots.
Harry
06 December 2001, 09:40 AM
#42
Scooby Regular
Join Date: Dec 2000
Location: West Yorkshire
Posts: 3,828
Likes: 0
Received 0 Likes
on
0 Posts
Harry,
I have recently fitted the Lambdalink and I was told pin21 was the correct wire to splice into. On my MY00 the wire is white too.
On cruise my car has the LED's going up and down all over the place. It is only when I am on full boost it gives a consistent reading the last green light on the Lambdalink (9% CO I think).
Damian.
I have recently fitted the Lambdalink and I was told pin21 was the correct wire to splice into. On my MY00 the wire is white too.
On cruise my car has the LED's going up and down all over the place. It is only when I am on full boost it gives a consistent reading the last green light on the Lambdalink (9% CO I think).
Damian.
06 December 2001, 12:47 PM
#43
Scooby Regular
Thread Starter
Join Date: Nov 2000
Location: 32 cylinders and many cats
Posts: 18,658
Likes: 0
Received 1 Like
on
1 Post
Yes the Knight Rider effect is the car running closed loop and rocking the mixture around 14.7:1 (stoichiometric) for economy and emissions.
Regarding the Knock link I think the 555 circuit is required to turn on a light long enough for you to see it as the effect is very quick.
http://www.california.com/~eagle/knock.html which also references the link posted earlier in the thread.
Regarding the Knock link I think the 555 circuit is required to turn on a light long enough for you to see it as the effect is very quick.
http://www.california.com/~eagle/knock.html which also references the link posted earlier in the thread.
06 December 2001, 05:23 PM
#44
Scooby Regular
Thread Starter
Join Date: Nov 2000
Location: 32 cylinders and many cats
Posts: 18,658
Likes: 0
Received 1 Like
on
1 Post
Went to pick up three LEDs today for my AFR meter and it works much better. Can see that it is not at all lean, by the time 15 PSI is reached at any throttle opening or revs I have 7-8% CO, and there is 6% CO with 10PSI or so. Much easier to see with three and only three different coloured LEDs. Thought about mounting some LEDs in one of the blanking sections above the fuse box next to the foglight switches. Or where the bright switch is. But in the meantime I'm putting it in a tiny little box a-la Lambda link.
07 December 2001, 03:11 PM
#46
Scooby Regular
Join Date: May 1999
Posts: 171
Likes: 0
Received 0 Likes
on
0 Posts
I'm confused on the voltage level you are measuring. Dawes devices offer a Air Fuel measuring device with 4 LED's
The indicators on Dawes meter are divided into .05 v increments as shown below:
First light: Red= .75 to .90
Second light: Yellow= .90 to .95
Third light: Green= .95 to 1.0v
Fourth light: Green= 1.0v and up
If you information on Voltages level is correct the Dawes will always ligt up RED 0.75 to 0.90 V
Either your voltages level is wrong or the Dawes device AFR is useless. I ordered one last week :c , price 55 US dlrs, I'm an electronic engenier myself, but like the design of the Dawes AFR.
I'll install the Dawes AFR when it arrive, and inform you on result.
Lars
The indicators on Dawes meter are divided into .05 v increments as shown below:
First light: Red= .75 to .90
Second light: Yellow= .90 to .95
Third light: Green= .95 to 1.0v
Fourth light: Green= 1.0v and up
If you information on Voltages level is correct the Dawes will always ligt up RED 0.75 to 0.90 V
Either your voltages level is wrong or the Dawes device AFR is useless. I ordered one last week :c , price 55 US dlrs, I'm an electronic engenier myself, but like the design of the Dawes AFR.
I'll install the Dawes AFR when it arrive, and inform you on result.
Lars
08 December 2001, 08:18 AM
#50
Scooby Regular
Thread Starter
Join Date: Nov 2000
Location: 32 cylinders and many cats
Posts: 18,658
Likes: 0
Received 1 Like
on
1 Post
I'm on my second attempt to fit now 3 5mm LEDs into a black blanking plate, and now I'm going to make a little daugther board for them to fit well just behind it and trail off a 4 core wire to somewhere near under the dash for the controller so I can adjust it as necessary. Told you my fabrication skills weren't good - should see my soldering attempt with a 25W iron and an 8mm bit on this job with as dense as can be layout on 0.1" matrix. Laughable. But it works and that's the important thing with no shorts and nothing loose yet.
09 December 2001, 11:36 AM
#51
Scooby Regular
Thread Starter
Join Date: Nov 2000
Location: 32 cylinders and many cats
Posts: 18,658
Likes: 0
Received 1 Like
on
1 Post
Daughter board worked well, but using standard LEDs they do not flicker in sequence like the faster action LEDs I used before. This works less well as they glow of different brightnesses and are difficult to interpret.
Will get some faster action 5mm LEDs. They fit quite nicely in the left hand blanking plate in the fog light switches cluster.
Will get some faster action 5mm LEDs. They fit quite nicely in the left hand blanking plate in the fog light switches cluster.
03 January 2002, 10:43 AM
#52
Scooby Regular
Join Date: Sep 2000
Location: London
Posts: 7,039
Likes: 0
Received 0 Likes
on
0 Posts
BTTT to ask:
John, you keep refering to the "datasheet", what is this? Is is something that comes with the chip? If so, I've just got my bits from Maplin and didn't get anything like this with it.....
I'm not completely clear about testing this thing....are you saying that you hook a 220K pot up to a 9V battery using the two outside pins to the battery terminals and the centre pin will be the output of the voltage as required to input into the LM chip on pin 5?
You mention setting up the reference voltages of 700mV on pin 4 and 900mV on pin 6 with the two pots but how to you actually achieve this?
Sounds like I may need to get myself a 220K pot?
Thanks in advance,
Matt
John, you keep refering to the "datasheet", what is this? Is is something that comes with the chip? If so, I've just got my bits from Maplin and didn't get anything like this with it.....
I'm not completely clear about testing this thing....are you saying that you hook a 220K pot up to a 9V battery using the two outside pins to the battery terminals and the centre pin will be the output of the voltage as required to input into the LM chip on pin 5?
You mention setting up the reference voltages of 700mV on pin 4 and 900mV on pin 6 with the two pots but how to you actually achieve this?
Sounds like I may need to get myself a 220K pot?
Thanks in advance,
Matt
03 January 2002, 10:47 AM
#53
You don't need the POT to set these voltages up, but just connect the AFR to 12V (or the 9V PP3) and adjust the 2 POT's fitted to achieve the volatge described.
The 220K POT mentioned by John is only used to simulate the Lambda input signal and hence get the LED's scrolling as you adjust the input.
The 220K POT mentioned by John is only used to simulate the Lambda input signal and hence get the LED's scrolling as you adjust the input.
03 January 2002, 01:00 PM
#55
Scooby Regular
Join Date: Sep 2000
Location: London
Posts: 7,039
Likes: 0
Received 0 Likes
on
0 Posts
Scott/John,
Sorry if I seem a bit thick but I assume that you have to set the two pots to the 700 and 900mV settings for the gauge to work accurately?
So presumably I need to monitor the inputs on pins 4 & 6 and adjust the pots until these voltages are matched?
Once they're matched, I should just be able to plug it in and it should display correctly?
Ta,
Matt.
Sorry if I seem a bit thick but I assume that you have to set the two pots to the 700 and 900mV settings for the gauge to work accurately?
So presumably I need to monitor the inputs on pins 4 & 6 and adjust the pots until these voltages are matched?
Once they're matched, I should just be able to plug it in and it should display correctly?
Ta,
Matt.
03 January 2002, 01:35 PM
#56
Scooby Regular
Join Date: Dec 2001
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
John,
I seem to remember that those types of display driver IC's can be chained / stacked together to form 10N bar displays.
You could then get a much higher resolution reading, and may look even more cool!
I'm just finding a datasheet - and I'll be back!
James
03 January 2002, 01:52 PM
#57
Scooby Regular
Thread Starter
Join Date: Nov 2000
Location: 32 cylinders and many cats
Posts: 18,658
Likes: 0
Received 1 Like
on
1 Post
Matt- correct.
James - you are even more of a nutter than me. Just because you have a display that gives you 2mV doesn't mean the sensor is giving that useful resolution or that the bargraph driver will be very accurate below its stated minimum 20mV resolution. What I am saying is just because you can doesn't mean you should unless you are even more of a nutter than me. With all this think about what INFORMATION you want out of it and design accordingly. Any more resolution is redundant. Hence I am only 3 LEDS now.
James - you are even more of a nutter than me. Just because you have a display that gives you 2mV doesn't mean the sensor is giving that useful resolution or that the bargraph driver will be very accurate below its stated minimum 20mV resolution. What I am saying is just because you can doesn't mean you should unless you are even more of a nutter than me. With all this think about what INFORMATION you want out of it and design accordingly. Any more resolution is redundant. Hence I am only 3 LEDS now.
03 January 2002, 02:26 PM
#58
Scooby Regular
Join Date: Dec 2001
Posts: 89
Likes: 0
Received 0 Likes
on
0 Posts
John,
I was not trying to be a nutter (honest :-))... I understand that its voltage resolution will not be increased (in terms of step size), but simply its dynamic range (more units of measurement)...
Additionally, I understand that for the AFR application this chaining idea is total ^&%* :-) But your earlier boost gauge etc ideas would (i think) benefit from more than 10 units of measurement.
Cheers
James
PS. Sorry, I accidentally hadn't read all the pages of this thread when I posted my first reply... I think that my comment kinda made more sense back then!
