AustinT

HI,
I am going to do some datalogging with a Innovate motorsports wideband. Besides logging the afr I would like to log the speed of the car. I have a t56 in a 89 camaro. The t56 speedometer output is a pulse. The wideband tuner can log an input up to 5 volts. How can I convert the output of the t56 into a voltage <5 volts so I can log it? Do the dakota digital boxes do this?
Thanks

If any of you are interested In the wideband I am using a second group purchase is current
https://www.thirdgen.org/techbb2/sho...hreadid=204651

onebinky

iTrader: (1)

Directed Electronics makes a pulse length extender, but I think it only outputs 12 volts. It's intended purpose is to provide a longer lock pulse for an alarm system. Many of the newer Nissans and VW's need it. Maybe check out their website to see if it will work for you. It's www.dei.com.

Matt

gnjones231

What your speedo puts out is actually a squarewave....not just a pulse. To convert your speedo signal to a voltage most people use an LM2907 chip. This is a frequency to voltage converter chip.

HTH

Dave

AustinT

What exactly do I have to do then Dave?
Thanks

gnjones231

Well, first you go here and print out a copy of the LM2907 chip.

http://www.national.com/ds/LM/LM2907.pdf

After you read and understand how to use the chip, you go buy one from Radio Shack or maybe online from Newark or Allied or Digikey along with the resistors and capacitors and probably some type of pc board to put all this stuff on. You then wire it up and check to make sure it works. You then hook it up to your car and your widband thing and go datalog! Oh yeah...don't forget to calibrate it too...

This is what's always recommanded when someone needs to convert a frequency to a voltage to dataog. I wonder just how many people can actually do this?

Good luck!

Dave

AustinT

Thanks Dave,

One of the Schematics at the website looks like it will work the way it is but I dont know for sure. Also do you know the difference in the LM2907 and the LM2917?
Thanks for the link. Im sure someone on thirdgen has done exactly what I need to do

gnjones231

It looks like the only difference is the built-in zener diode. A lot of times when you have the same device listed with different nomenclature, it's usually due to different operating temperatures, or maybe sometimes higher accuracy, but in this case, it's just the internal zener.

If you get it built and working, let us know so we can give you an applause.

Dave

Doctor J

When it's finished it may look something like the one on this page (only without the excess wires - I was experimenting with that one):

http://www.corvetteforum.net/c4/doctorj/carwb.htm

Page also shows a datalog of RPM & WB Volts vs time. Note the need for a reasonable sample rate on the logger in order to get useful results.

Have fun.

AustinT

I visited with A EE from Southern Utah University . I know how to build the circuit. Does anybody know where to order the chips for the circuit. The EE gave me all of the resistors and capacitors for the circuit, he didnt have the chips.

I know I can get them from Digikey, but they have a 30 dollar Min order I think

gnjones231

AustinT give me an email with your name and address, and I'll send you a couple.

Dave