electronics students/pros, re: narrowband

[MILITISINVICTUS]

I've got this narrowband gauge sitting here with no purpose. Is there a simple electronic component out there which would convert battery voltage down to a voltage that could be displayed on a narrowband? I guess we'd want 12V to become .5V so that would set a dead-center value on the gauge. 14.5V becomes 1V, 10V becomes .01? Something like that. You get the gist, run with the idea for me if you know this type of stuff.

If you've got any other ideas for what info a narrowband's display could be made to show, may as well hear that too.

 

[Splitpi]

Yes it can be done... no it may not be useful. You need to just drop the voltage by 12V and then devide the signal by 2.5. The problem arises in the fidelity of the resultant signal. Also there is a very strong chance of noise getting onto the signal lines and causing the gauge to bounce. Hence you would need to sum the value over time to get an average reading over say a second or two. If you want instanteous changes that are very accurate, then its not worth it. If you want a ball park reading... then it will work just fine.

 

[MILITISINVICTUS]

What's the proper term for this component? Can one component do this, or would it require several components to get the desired effect?

 

[Splitpi]

Its been a while since my electrical engineering classes.... but it'll require a few components and its not overly complicated to design. I cannot be of more help however, as I don't have the time to write up the circuit for you.

 

[drivemusicnow]

The circuit is pretty simple, but there are a lot of different ways to do it.

Also, there are ways to make it more stable so you don't run into the problems that splitpi was talking about. Let me think about it for a little while, and I"ll try to come up with something for you.

By the way, if you have a DC power supply, it would make this a lot easier, because you could verify exactly what voltages give you want readings on the Narrow band gauge (does it have a digital display? IE at stoich does it say 14.7? because if you could convert it so that the digital diplay actually reads volts, that would be pretty cool actually IE 12 volts reads 12 "AFR" on the gauge)

 

[drivemusicnow]

Okay, a couple things. First of, as most people know, a narrowband o2 sensor has a large variation in voltage between 14 and 15 AFR, but very small variation between 11 and and 14, adn 15 and 17 AFRS.

This means that you would have to condition the signal for the 3 seperate slopes

Here is a picture:

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So, you have a couple different options. if you just want an output that would be useful to you (for example you don't care what actual number is shown, as long as you can convert it to something useful in your head) I would use just the center portion of the graph, and control the voltage with some resistors such that .9 volts is 15 volts at the battary, and .1 volts is 10 volts at the battery. This is pretty easy, but would give you a inverse relation when you look at the AFR numbers compared to actual voltage (as in, a 14.9 AFR means a lower battary voltage than a 14.3 AFR. This isn't a big deal as long as you just want it for your own use)

To make it actually accurate as in 12volts = 12 AFR, you would have to sepearte the signal into 3 parts, and condition each seperately.You would also need to invert the voltage, such that 12 volts is a lower Signal voltage than 14 volts. The problem with this is that for the parts of the graph that are relatively flat, you would need to be very accurate with your signal conditioning, because very minute changes equate to large variations in output.

I think this is a bit more complicated than you really want, but let me know what your thoughts are and we can go from there.

 

[MILITISINVICTUS]

It's a PRIME Instruments gauge, their website is a joke, so I likely won't be getting any good data from them. It has ten bars that will light up, going from "lean" to "rich." I'd think an odd number of bars would make more sense..

The idea would pretty much be to just turn the gauge 90' and have it illuminate left to right: "low volts/cranking" -> "normal" -> "alternator charging the system." Our budget should be limited to say 33%-50% of a new autometer voltage gauge (which I am not buying because I don't really NEED one, this is for fun).


As for tools at my disposal.. hmm. I have a 3 to 7.5V (2A) adjustable adapter, which doesn't look useful at the moment. Maybe I can use my multimeter to organize a bunch of old AA/AAA batteries in order of crappiness and see if I can come up with a rough 0-1V correlation on the display. -Or will the amperage be too weak? I also have a soldering iron as needed.

The circuit is pretty simple, but there are a lot of different ways to do it.

Also, there are ways to make it more stable so you don't run into the problems that splitpi was talking about. Let me think about it for a little while, and I"ll try to come up with something for you.

By the way, if you have a DC power supply, it would make this a lot easier, because you could verify exactly what voltages give you want readings on the Narrow band gauge (does it have a digital display? IE at stoich does it say 14.7? because if you could convert it so that the digital diplay actually reads volts, that would be pretty cool actually IE 12 volts reads 12 "AFR" on the gauge)

 

[MILITISINVICTUS]

So if I follow you, what would make sense when dealing with this inverse relationship, is to spin the gauge so it's rich on the left, lean to the right. As for inputs, we want to focus on the battery's operating voltages (say 10V to 15V? 11V to 14V?) being associated with the gauge's 14:1 to 15:1 AFR input voltage range. Everything outside those values would just peg the gauge to one side or the other, which should be fine.

If I'm on track, lead the way.

Okay, a couple things. First of, as most people know, a narrowband o2 sensor has a large variation in voltage between 14 and 15 AFR, but very small variation between 11 and and 14, adn 15 and 17 AFRS.

This means that you would have to condition the signal for the 3 seperate slopes

Here is a picture:

You must be logged in to view this image or video.

So, you have a couple different options. if you just want an output that would be useful to you (for example you don't care what actual number is shown, as long as you can convert it to something useful in your head) I would use just the center portion of the graph, and control the voltage with some resistors such that .9 volts is 15 volts at the battary, and .1 volts is 10 volts at the battery. This is pretty easy, but would give you a inverse relation when you look at the AFR numbers compared to actual voltage (as in, a 14.9 AFR means a lower battary voltage than a 14.3 AFR. This isn't a big deal as long as you just want it for your own use)

To make it actually accurate as in 12volts = 12 AFR, you would have to sepearte the signal into 3 parts, and condition each seperately.You would also need to invert the voltage, such that 12 volts is a lower Signal voltage than 14 volts. The problem with this is that for the parts of the graph that are relatively flat, you would need to be very accurate with your signal conditioning, because very minute changes equate to large variations in output.

I think this is a bit more complicated than you really want, but let me know what your thoughts are and we can go from there.

 

[Splitpi]

Kinda, the problem is that the narrow band maxes out at ~1V. So the gauge will read rich as even at 12V it is still higher than the 1V max rich O2 reading. So you would still need to offset the voltage by 12V and then you could read from 12-13V or if you devide it further in half you can go from 12-14V. Make sense? I wish I had the time to make the circuit... but it has been far too long for me.

 

[VelocitàPaola]

Sounds like you just need a simple voltage divider circuit to proportion ~0V-14V to ~0V-1V.

It shouldn't require more than a few resistors and/or a potentiometer.

 

[drivemusicnow]

Ah, so it's just a blinky light gauge? Then you're really going to need to figure out what voltage range operates what lights for the gauge to do you any good.

Does it have a digital display? because that would make it easier to figure out.

The spinning the gauge option is genius and will save a lot of me trying to remember my circuits class.

SO, if you're trying to take voltage from lets say 10v, to 15v, and reduce it, linearly to a .1 to .9voltage range... hmmm, well, a simple resistance network can give us 15 volts = to .9 if we use a the following:

12V input- 9.35Kohm (+V source) 6.45Kohm, Ground.

The problem with this is it only gives us .6 volts signal from a 10volt source.

I will have to get back to this as I'm a bit short on time right now.

 

[MILITISINVICTUS]

Yes, it's a stacked bars style blinky light gauge.

I don't think my little idea to use dying batteries to fake a signal to the gauge will work. having two + inputs and one - output wire, I'd have to drive it using a 12V source, as a little battery won't power the gauge at all. I don't have a capability to step down my 12V at will.

Any other thoughts?

 

[MILITISINVICTUS]

As to the part of the original post regarding other possible uses for the gauge, I came up with another. Pretty limited value, but I could tie the signal wire in to the FPR solenoid, and the gauge should be a on/off indicator of whether my cyclone's butterflies are activated.

I'm not sure whether that little draw would disable the solenoid, or if the power (how many volts in that circuit?) would burn the gauge up.

 

[Defiant]

http://www.scirocco.org/tech/misc/afgauge/af.html
http://autospeed.drive.com.au/cms/A_0217/article.html?popularArticle