i found this link this summer that describes how to make an A/F meter yourself using the same parts as the comercial one, but for about only $4. then we made one w/ my friend and it seemed to work fine he kept the 1st one and i made a 2nd one, but broke the chip so i had to wait before i can make one again. then recently i found another website with a much better diagram, but i think it's down now. here is the diagram tho .
this guy is using different resistors, so his range of voltages should be different. does anyone know how to calculate what the range of the voltages displayed on the LED will be? i've tried reading the spec for the driver ship, but i cant understand any of it. please help if u can, or maybe u have the comercial gauge and could tell me the real values for the resistors used.


[Modified by max, 5:08 PM 9/23/2001]

 

All you built was a volt meter. Is this the one Kahren has?

 

National.com gives away free samples of LM3914 chips. I have a bunch of them in my closet.

Dustin

 

so do i if anyone asks, im the head design engineer for a research experiment at VA Tech...
but seriously now, can anyone tell me how to calculate the measured range or how to choose the right resistors for a given range?

Tbone, kahren has the first one we made. i made the same one too, but then i broke the damn chip <--me. now i made a new one using the second diagram.

 

I have all the stuff I need to build it, and actually, I'm planning on increasing the resolution of the meter (using two bargraphs in series), to give more accurate readings..And also I plan on adding a Piezo alarm for when the car gets too lean.

But I haven't put it all together yet...and I really don't even know if it'll work. I've been reading about using the two LED bargraphs in series in the LMP3914N manual...and I would assume the alarm would be as easy as a relay..

But I'm not an electronics expert, and if I could run my plans by you guys, and maybe we could bounce ideas off each other, that would be cool. What do you think?