diy af meter help
 

Who has made a diy a/f meter? Care to share what schematic you used? I'm looking for one that has been successfully followed since the ones I've tried (on the LM3914N chip) haven't worked. Not sure if I'm doing something wrong, or I just need a good diagram.

Thanks

Re:diy af meter help
 

i'm gonna be using the setup at www.diy-wb.com but that's a WB not an A?F gauge

Re:diy af meter help
 

The only ones that I have seen are the those. I have seen them work, but I can't say that I have made one on my own.

Here is the schematic that I found most referenced..

http://www.scirocco.org/tech/misc/afgauge/af.html

Re:diy af meter help
 

that's the one I'm building currently. My chips are on their way from singapore. When they get here I'll let you know how it turns out. I've ordered 5 chips, and I'll be making 3 gauges initially. does anybody know where I can get a 4.7k ohm potentiometer to adjust the resolution? radioshack discontinued them.

Re:diy af meter help
 

I just got the 10k ohm pots. Scale em down and they should do the trick ;) Why would they even make a 4.7k pot - some special use?

Hmmm. I used the same reference. I wonder what I did wrong?? I gues it is time to get a new breadboard and start over.

Re:diy af meter help
 

I made/installed A/F meter based on http://www.scirocco.org/tech/misc/afgauge/af.html ... and it works great!

Re:diy af meter help
 

Thanks! That is the response I was looking for. Now I know the schematic is good, so I must have done something wrong. Time to try again.

Hmmm. I think I used a 12v regulator, for one thing. I guess that probably would have had something to do with it. Da'oh! Looks like I did everything else right, except for the 10kohm pots which shouldn't affect anything...

Re:diy af meter help
 

I made from the schematic at http://www.buckeyetriumphs.org/techn.../AFMonitor.htm
It's a really good implementation because it's nonlinear.
I made mine on a veroboard but I drew a PCB layout. If anyone's interested I'll post it here.

Re:diy af meter help
 

I made one on a tester board. It worked for about 2 weeks. I didn't use a voltage regulator, so I think I blew the LM3914N. Here is a pic

http://users.adelphia.net/~cybrphrea.../afcircuit.jpg

I'm going to rebuild another one using LEDS built into my rearview mirror that should be scalable once I get my TE WB built. But for now, I just want to make sure I'm in the right range and don't blow the engine due to detonation, which is all regular A/F guages are good for anyway.

Re:diy af meter help
 

wiring that up into your mirror is going to be a bitch, but the end result will be cool. I can't decide if I want to go with a bar of one color of leds or just single leds so I can make them whatever color I want.

Re:diy af meter help
 

you should make a happy face. you know, happy when stoich and sad when lean.

Re:diy af meter help
 

i have a schematic for one that uses a $12 digital LED panel meter and gives a numerical readout if anyone's interested.

Re:diy af meter help
 

id like to see that

Re:diy af meter help
 

Scarecrow
would you mind shootin that schematic of yours over to me?

thanks

Re:diy af meter help
 

i lied. the panel meters are $15 now, not 12.
they're available at www.web-tronics.com or www.allelectronics.com.

here's the schematic. standard disclaimer applies, don't steal my ---- and sell it. it's for personal/nonprofit use only.

BOM (with web-tronics part #'s):
R1 100k multiturn trim pot, WIW1012-100K $0.89
R2 10K 1/4watt resistor, RA10K, $0.07
C1 0.1uf capacitor, 23BK410, $0.19
C2 1.0uf capacitor, TAC005, $0.87
U1 LM7805 voltage regulator, 7805, $0.86
M1 CX102B panel meter, CX102B, $14.95 (10+, $10.95.. a group buy of the parts may save a couple bucks)
find yourself an enclosure for it and you're good to go.

http://www.imagestation.com/picture/...c/f9f16bf4.jpg
the trim pot can be set with an ohm meter too. there should be 90K between the O2 input and the center pin and 10K between ground and the center pin. fairly simple.


i'm planning on putting some of the schematics i have up on kyle's website. i have stuff like EGT drivers, rev lights, boost controllers, water injection controllers, and i currently have a traction control module almost done.

Re:diy af meter help
 

I don't like loading the O2 sensor like that, the internal resistance is low, I'd prefer using an opamp buffer.

Re:diy af meter help
 

we'll get all that stuff on my site whenever we get around to it, it shouldn't be too hard.

Re:diy af meter help
 

say what? How do you buffer it? And do the comercial gauges do that or do they just read straight off of the sensor like I was going to do?

Re:diy af meter help
 

http://scirocco.dyndns.org/tech/misc...ge/diagram.jpg

that doesn't show where you ground it? I take it that you can ground it wherever as long as it's not between the resistors and the lm3914?

Re:diy af meter help
 

I'm not sure if I understand your question. Just ground everything on the board together, and then run a wire to any good ground on the car. I was going to probably run three wires together to the pos, neg, and signal from the sensor, altho you shouldn't need to do that. You can just ground somewhere closer if you want.

Re:diy af meter help
 

I installed it and it read all the way rich all the time, except when I let off the gas and it's in gear, then only one light is on. I have the pot to adjust resolution, and when I turned it all the way one way 4 or 5 lights were on with 0 throttle in gear and now I have it all the way the other way, is my car just really rich?

Re:diy af meter help
 

I guess that is why they aren't really designed for tuning! Only way to know for sure would be to use a multimeter to test the voltages and make sure your graph is displaying properly. Aren't you still NA? If so, and the graph is correct, I don't think you should be that rich. Well now that I know it works (somewhat), I guess it is time to get my butt in gear and buy some new components so I can start over!

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if I grounded it all after the resistors would that mess things up? I'm going to redo that and see what happens.

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ya, I'm NA. I think the richness is due to the high water content inside my cylinders thanks to my leaking head and block connection. I'll lean it out with my diy afc and see what happens once I get the gauge working.

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last time i ordered 5 chips, ending up burn off 4 chips before i found out the chips in this graph was place WRONG. u will have to turn the chip around. :P

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how do you mean? did your gauge work at all? and lights going on? mine lights up and all, and changes too. is the crescent in the side of the lm chip at where it says number 1 in the diagram or not?

Re:diy af meter help
 

yea that little dot at the corner is #1...
what happened is that right after i power it up, all the LED became kinda dim..then the chip gets real hot and burn off.
so i looked up the diagram of the chip and found out i will have to turn the chip around, so #1 became #10, #9 became #18.. ???

Re:diy af meter help
 

mine stayed on for about 30 minutes while i was messing with it, I must have done it right.

Re:diy af meter help
 

Hmm. Kyle, so did you wire it according to the diagram, or do you have your chip upside down? Yes, the crescent should be on the side with pin 1.

Donald125, What do you mean, they "burn off"? Do they smoke or something, or just stop working??

Re:diy af meter help
 

they heat up, smells then unit die. :(
trust me, i`ve been working on these electronic ---- for 10 + yrs. i`ve also looked up the dirgram of the chip.

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That is funny, because I've got the whitepaper from NS, and the chip is isntalled in the same orientation in their examples. The only difference I saw in their diagram, is that the leds seem to have their polarity reversed.

Re:diy af meter help
 

oh welli got mine throught the internet...
might be i read ---- wrong ???