ABS->Speed converter

[Pet]

Hi, I am testing a frequency to voltage converter with IC LM2907 for logging wheel speed (from ABS sensor) into VEMS by using free A/D input. It's quite simple circuit with this IC (only 8pin SOIC package + a few resistors/caps). You can adjust Hz/V ratio, so there's no problem to adjust circuit to any ABS sensor. See logged data (note: Fuel Pressure is Wheel Speed; in vems.ini is added multiply constant to get real km/h).  There is still a litlle problem with noise when the wheel isn't turning (the IC triggers from +/- 20mV), so I'll try some filter... If there is some interest, I can publish more info about it.

[[email protected]]

Cool stuff.

Have you seen the wheel speed input stuff via the keyboard connector?

[Pet]

Yes I have. But I would like to use some FW independent solution and why don't use a free A/D input, which has almost every Vems unit... ;)

[[email protected]]

Its a good point, every VEMS has the keyboard connection internally, but using your method means that you don't need to open the box.

[lezsi]

Such thing is good to have.
One speed input is not enough for many apps anyway  :)

[dnb]

I too have played with the LM2917 chip (very similar to the one you use) to convert my tacho from direct coil drive to one VEMS can drive directly, and it all works nicely, apart from a bit of noise as you describe. 

Neither of my current VEMS cars has ABS, else I would be using the same strategy for getting wheel speeds into VEMS.  I could do with getting some ABS equipped hubs for the Impreza soon, so would like to hear about what you're doing, although getting the engine built and running is the first priority!

[Pet]

Yea of course, running engine is the most important :)
Anyway, noise problem seems to be solved, so I'll make some longer testing now. But I have also a lot of work to do on my Vems unit , because I've created my own PCB with Bosch 55 connector integrated into old Siemens ECU box from Opel C20XEV engine (therefore I can use the stock wiring loom from my C20XE M2.8@turbo engine). It's already running more than 2 months without any problems, so it seems it's partially success :)

[gunni]

How are you connecting your box and the vems unit together?

[Pet]

As I wrote, I created my own PCB with VEMS hardware (of course with many modifications based on my special car setup, there is no EGT circuit, only 4x MOSFET driver,no IGN IGBTS, no LCD output, etc). Of course, this unit (Bosch55 pinout) is then compatibile only with C20XE M2.8 wiring loom (which I am using).

[gunni]

Ah I see, very nice :)

[[email protected]]

So you've modified the design and implemented it yourself?

[Pet]

Yes, I can say. On the last xmas, I wasn't so busy (on my ma-in-law visit :-D ), so I had started create a new schematic, components to library etc. in Mentor Graphics, because I needed to learn this PCB SW due my new job. So I joined pleasure with engagement and after about 1+1/2 months of work was my new PCB on the desk ;)

[mr_g]

Nice.