mops Posted November 27, 2003 Share Posted November 27, 2003 Hello. Did anyone builded one of those according to the article on this site ??? I need more info on where do i connect it up to and how do i calibrate it..... can anyone help ??? Quote Link to comment Share on other sites More sharing options...
99obw Posted November 27, 2003 Share Posted November 27, 2003 I can probably help if you can be more specific. My senior project in college was a computer interfaced oxygen sensor/thermocouple, and I interned at a company that makes car computers for GM and Ford. Quote Link to comment Share on other sites More sharing options...
mops Posted November 27, 2003 Author Share Posted November 27, 2003 great. check out this link http://usmb.net/repair/?CurrentDirectory=FOLDER_3f35c591bdc2e0.78531895/&FileType=Article&File=ARTICLE_3f7bb215ea91b8.39054402.art do you think it's worthwile ??? how accurate would it be ??? - i do not need any exact values, just i want to know when it's leaning off to the stage that it is unsafe to run that much boost. Quote Link to comment Share on other sites More sharing options...
WJM Posted November 27, 2003 Share Posted November 27, 2003 I wonder if anyone is willing to build these for those who are interested....Like me...who doesnt have time to go to radioshack and get the parts and put it together. :-\ The connctor there...which color wire does what? Yellow input? Red 12v input, and the green as ground? Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 27, 2003 Share Posted November 27, 2003 On 2-3 occasions when I built something for myself (LED xmas lights, pirate TV antennas,etc.) I would always build 2-3-4 of them and test then sell the xtras - that way mine was usually free! Quote Link to comment Share on other sites More sharing options...
mops Posted November 27, 2003 Author Share Posted November 27, 2003 yeach, i can make that - thats easy. but i dunno where to plug it in or how to calibrate it, etc... Quote Link to comment Share on other sites More sharing options...
meep Posted November 27, 2003 Share Posted November 27, 2003 I'll take a look at it. I'm between jobs right now and could use the $$. Mike Quote Link to comment Share on other sites More sharing options...
meep Posted November 27, 2003 Share Posted November 27, 2003 ok-- this is basically an adjustable voltmeter. the chip is a standard driver for bar graph meters. This circuit is designed to be calibrated.... but I have no idea to what. No data for quantitative adjustment--- just shows changes in... O2 sensor readings??? For air/fuel mix it'd need to compare MAF readings with injector pulse width or something-- too many variables affect the above idea to make it accurate. Might look cool, but... Mike Quote Link to comment Share on other sites More sharing options...
mops Posted November 27, 2003 Author Share Posted November 27, 2003 yeach, thats what i thought.... Quote Link to comment Share on other sites More sharing options...
grounded1 Posted November 28, 2003 Share Posted November 28, 2003 This air fuel meter has to operate like the over the counter types. All it is, is a led meter that reads up to 1 volt. The Autometer gage reads up to 1 volt in .05 volt increments. That is why it has 20 leds. That adds up to 1.0. The meter on this plan has ten leds so each increment will be a tenth of a volt (.10) The closer to 1 volt the richer the mixture. As for calibration, according to the subaru service manual the range of the O2 sensor is .2 volts to .7 volts. The adjustment pots on this homemade job just set the range. You could probably do it by eye so that at the richest WOT it peaks the red leds. Same for lean at opposite side of the led scale. The Autometer air fuel gage I have in my car never goes to the factory full rich because the suby set up never hits 1 volt for full rich. So I'm always a couple led's short but I know its full rich for my setup. This homemade job at least can be tailored to any vehicle. I'll bet the parts to build it are a fraction of the price of an after market gage. Pat Quote Link to comment Share on other sites More sharing options...
99obw Posted November 28, 2003 Share Posted November 28, 2003 I have seen those before. I think it is a fun gadget, but certainly not capable of precise measurements. If you have the time and money go for it, it would be fun. I think it would be nearly impossible for a DIYer to do a meaningful calibration. First of all, what does each LED mean as far as oxygen concentration goes? The oxygen sensor I worked with gave a signal related to the percent oxygen (from 0% to 20.9%) and the temperature of the element, and my electronics calculated the oxygen concentration and output it to an LCD in %. I don't think the automotive sensors work in the same way. I think it gives you a signal related to oxygen content over a very small range. The only calibration I can think of is to feed in a voltage corresponding to the voltage you expect the LED to light at, and adjust until it does. A quick look at the schematic leaves me with some unanswered questions: 1. Is the 2.2uF cap on V+ supposed to operate as a power decoupler? If so, it is connected incorrectly. 2. Does the LM3914 require power supply voltage regulation? If so, none is equipped. A little bit of low pass filtering on the input would reduce the fluctuations of the LEDs due to normal noise, but that may be built in to the LM3914. You may be able to add a precision voltage reference and use the DIP switch to add a calibration feature. I can take a closer look as time allows. Quote Link to comment Share on other sites More sharing options...
99obw Posted November 28, 2003 Share Posted November 28, 2003 That schematic has at least one error in it, which makes me want to take a good look over it. I will be able to Sunday night. For those interested take a look at the LM3914. Quote Link to comment Share on other sites More sharing options...
meep Posted November 28, 2003 Share Posted November 28, 2003 yea, noticed that cap on V+. Decouple DC? No... The 3914 is a neat chip--- I've used it in variable bench supplies for both V and I readouts. It does not really need a regulated V+, but it is saddled with the job of dissipating LED current. at 14V it'll get a bit warm if it's driving several LEDs. Or you could run it in"dot" mode, so only one lights at a a time. I typically regulate to 5V-- it's only another $0.59 for the LM350 (right?) and a few cents for a zener to create an expanded scale Vmeter.... In a noisy DC environment such as a car, I'd think a regulator, parallel caps and coil would be a nice thing for any solid state stuff. Mikey Quote Link to comment Share on other sites More sharing options...
mops Posted November 30, 2003 Author Share Posted November 30, 2003 how about, instead or building led-based thing.... an analogue voltometer, with a scale from 0 to 1.0V again, the exact measurment is not possible, however the rate of change is what's important.... and how does it vary.... basically, I want an indication, when is it too lean... otherwise i dont really care. so, from the sensor... low voltage - rich, and high voltage - -lear or vice versa ???? FFS, i could even connect my Digital multimeter there temporairly, to see values.... grrrrrrr..... Quote Link to comment Share on other sites More sharing options...
mops Posted November 30, 2003 Author Share Posted November 30, 2003 which leads me to my next point.... then, modyfi MAF reading to trick the ECU into providing more fuel (while running more BOOST :banana: ) :headbang: :grin: :grin: Quote Link to comment Share on other sites More sharing options...
mrtoyou7747 Posted December 2, 2003 Share Posted December 2, 2003 This looks like a real simple thing to make if it works. I have a couple of questions. 1. Where do you connect it? 2. If you connect it to an exsisting sensor what do you do with the plug which is on the sensor to start with.? Seems to me that you would need to measure this sensor voltage in circuit where the ECU can still use the sensor voltage to do its thing. Quote Link to comment Share on other sites More sharing options...
mrtoyou7747 Posted December 2, 2003 Share Posted December 2, 2003 This looks like a real simple thing to make if it works. I have a couple of questions. 1. Where do you connect it? 2. If you connect it to an exsisting sensor what do you do with the plug which is on the sensor to start with.? Seems to me that you would need to measure this sensor voltage in circuit where the ECU can still use the sensor voltage to do its thing. Quote Link to comment Share on other sites More sharing options...
grounded1 Posted December 2, 2003 Share Posted December 2, 2003 The Autometer air/fuel gage is a 3 wire hook up. 12v, ground and sense wire that connects to the output of the O2 sensor. It connects to the output wire of the O2 sensor. That is the one that only puts out 0 - 1volt max. I assume the kit works the same but there is very little information about it. Be careful. Thats why i just bought one. Pat Quote Link to comment Share on other sites More sharing options...
99obw Posted December 2, 2003 Share Posted December 2, 2003 Originally posted by mrtoyou7747 This looks like a real simple thing to make if it works. I have a couple of questions. 1. Where do you connect it? 2. If you connect it to an exsisting sensor what do you do with the plug which is on the sensor to start with.? Seems to me that you would need to measure this sensor voltage in circuit where the ECU can still use the sensor voltage to do its thing. Sorry I haven't had time to take a closer look. I can tell you that the cap is connected incorrectly, so if you decide to build it just ask and I can tell you how to connect it. To answer both of your questions, it will connect in parallel with the ECM. The sensor, your gadget, and the ECM will all be connected together. I would be tempted to make a harness that has a connector off of a sensor and a connector off of a wiring harness so that you don't have to cut any wires on the car. Quote Link to comment Share on other sites More sharing options...
Snowman Posted December 2, 2003 Share Posted December 2, 2003 I'm considering doing this on my car, which is carbureted and therefore doesn't have any ECM, or an O2 sensor. I've got a Y-pipe from a fuel-injected car on it, which has the O2 sensor, but I need to know what to supply the sensor with. Does it just get 12 volts, or do I need to regulate the voltage? I like the idea of just hooking up an analog voltmeter, but where could you get one that just reads 0-1 volts so that it would move enough to be noticable? Quote Link to comment Share on other sites More sharing options...
99obw Posted December 2, 2003 Share Posted December 2, 2003 A three wire sensor has heater +, heater -, and signal. A four wire sensor adds a signal ground. AFAIK the heater is just 12V, but I think it is shut off after the sensor comes up to temp. If I were going to add an O2 sensor to a carbureted car I would use a 4 wire sensor. Fuse the heater + wire for sure. The sensor won't operate until it reaches something like 600*. Quote Link to comment Share on other sites More sharing options...
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