xpndbl3

iTrader: (5)

i got some plans off "deadbird".

I can not for the life of me seem to find a place to sell me the "LM 3914" IC chip in order to build this thing. ANy thoughts on where to order the 10 leds needed for it as well cheaply?

thanks
steve

1986redbird

I built one of these about a year ago, it seemed quite eratic on the readings but it could have been something I did wrong. I think I still have one of the chips laying around somewhere if I do I will send it to you for a really good price (free), the l.e.d.s you can get from "radio shack". I would recommend just getting one of the gauges from summit or somewhere like that, it will cost a little more but will look alot nicer when finished. P.M. me with your mailing address and I'll put the chip in the mail to you (providing I can find it).

Danno

The LM 3914 IC has been out of production by Signetics for a while. You might try NTE, they offer a cross reference for many obsolete devices. Found my cross book, it's a NTE 1508. There are lots of NTE dealers around.

xpndbl3

iTrader: (5)

ok thanks guys i will try to find the NTE 1508 chip.

Also isn't that O2 guage supposed to bounce around a lot anyways? I have seen the Autometer ones hooked up on cars and it never stays in one spot for very long and flips from rich to lean, although it pauses on a reading for a while though.

Danno

Yes, it's normal as the O2 sensor constantly updates the ECM. If you use a digital voltmeter and monitor it you take several readings and just average it out. I have used my oscilloscope and it's a little easier. Don't forget that you can also place the stock ECM in the field service mode and the SES light will tell you if it's lean or rich also.

Rustydawg

Has anyone tried an analog meter instead of the LED bar graph?

I've got an old tach that I'm converting to an O2 sensor display. I'm using an Op Amp to buffer the O2 sensor output, making the meter about 1 volt full scale.

I won't be finished or installing it until spring because the car is parked. I suspected that the voltage would be bouncing around a fair bit, but has anyone else tried this setup?

It will probably be a temporary thing for tuning that I can add / remove from the car quickly and easily.

Danno

As long as the input impedence of the meter is 10Mohms or higher you should be OK. Lower input resistance loads the sensor down or will actually destroy the unit itself.

Rustydawg

No problem, the O2 sensor goes straight into the non-inverting input of the Op-Amp so the input impedance will be right up there.

Once I get it running I'll post the results.

What about these so-called 'wideband' O2 sensors, they sound more useable for tuning, but I've only heard about them used with Dyno sessions. Are they readily available?

Apeiron

Wideband O2 sensors work in an entirely different way to "normal" O2 sensors so you'd need an entirely different circuit.

Check out http://www.diy-wb.org

Rustydawg

Apeiron, thanks for the link, there's lots of good info there.

The Wideband sensor is definitely a different bird. I'll have to price one of those puppies out. It looks like the way to go for sure.

xpndbl3

iTrader: (5)

Did you get my PM by chance?

Steve

1986redbird

I got it, sorry for not reply'n. I will send you what I have tomorrow, I'm going to hunt it down tonight.

xpndbl3

iTrader: (5)

hey thanks a lot redbird. I really appreciate it.

Steve

1986redbird

xpndbl3: lost your e-mail address, but I am sending you the parts I have. the chip, 10 led cluster, potentiometer. should be there in a few days. GOOD LUCK. Perry G.

Apeiron

Signetics? Isn't the LM3914 originally from National Instruments? The LM3914 has been discontinued but the LM3914-1 is still available.

xpndbl3

iTrader: (5)

i think it's originally from signetics, although national intstruments makes a "like" one. I haven't been able to find a shop in my area to get one....

But redbird to the RESCUE!!!


Steve