stevej88na

There hasn't been an official thread here about this project, only one burried in a SevenStock 9 thread, so some people already know about this. Anyway, the original idea was to build an inexpensive display so I could monitor different sensors on my RX-7. I've since turned it into a data acquisition unit as well, and it can now log four sensor signals at 10Hz for 25 minutes. Basically, a small cellphone LCD screen shows sensor data in real-time, and buttons let you do things like start and stop logging. Here's an example of the output:



( see the full sized version here )

and here's the evolving how-to page:
http://howto.globalvicinity.com/gv_w...i=82&co=1&vi=1

I've been having a lot of fun playing with this thing so far, and what's most impressive is parts cost only $30 to $60 depending on the components you add. I've done all the design, software, and hardware, and am putting the files up so others can build one of these for themselves. My friend wants one to log things like body roll with different suspension settings on the track. I'm using mine to monitor my MAF output in kg/hour of air, the boost voltage on my VDI solenoid, and some temperature sensors.

If you build one of these and make custom look-up tables, let me know and I can add it to the official list. I've got temperature, Mustang MAF, distance, and AEM wideband look-up tables so far.

fritts

iTrader: (5)

I absolutely love what you have done. I would like to do something similar but I'm an ME and sparky stuff is pretty foreign to me. Do you have a listing at digikey or somewhere to buy a kit of the parts? It looks like your running everything off a breadboard still will you be testing and selling the boards. Your about one step away from a full gauge cluster display which is what I would really like to do.

Do you have to have any special programming to change the tables and program the chips?

papiogxl

iTrader: (6)

I plan on using this:


It uses the megasquirt's output, and is customizable. If I hadn't gone with the megasquirt I would have definitely gone with your idea. I only wish I had more experience with making my own circuits, and writing code.

Also check out pengarufoo's lcd dash, it is pretty sweet, but almost requires a standalone, though you could do a variant with a controller similar to yours.

/ threadjack.

stevej88na

Thanks! As for being ME, I say more tools in your belt can only help; if you're interested, don't let inexperience hold you back, because this kind of thing really doesn't take much time to get the hang of, and there's so little money involved here that frying a chip or two won't break the bank. You don't have to do any circuit design or programming if you don't want.

There's a DigiKey parts list ("Bill of Materials") on the how-to page, which lists the parts to make the layout on there. That layout is quite compact (my driving force was to get it to fit in a gauge pod) and might be challenging to solder. I'm currently making a less compact layout that won't fit in a gauge pod, but should be easier to put together. As for selling, I'd prefer it if others would try building these themselves, but I may offer complete systems as a "paid favor."

Uploading look-up tables to the device is done with the Java program I posted. Actually creating new LUTs from scratch boils down to figuring out what to display at various sensor voltages. I've been using Excel to make them so far, like this:

1. Find a few values at known voltages
2. Fit a curve to the data
3. Use the curve to expand over the entire voltage range
4. Copy and paste the table into a text file, and upload

For instance, here's a snip of my temperature sensor table:

The left column is the table address, from 0 to 1023, which represents the sensor's voltage from 0V to 5V. The right column is the value to display at that voltage. Sometimes there's more effort involved, like when a sensor's useful range isn't within 0-5V, and I provide instructions for fixing that on the circuit schematic.

fritts

iTrader: (5)

Do you plan on producing PCB's for it? Also is there any good info on how to interface the daq's with the LCD that's the part I don't understand. I have been planning to run AFR and 2 EGT Amps, and would like to have some sort of display for them.

fritts

iTrader: (5)

Also what are you programming everything with?

stevej88na

The way I've been doing these projects is with Atmel's ATmega series microcontrollers; you can either program in assembly or C. All my designs fit ExpressPCB's "miniboard" size, meaning any of us can order 3 boards for $51. The layout file I've posted will get you the PCB's usually within one week. For some more info, check the "Resources" section of my VDI solenoid project:

http://howto.globalvicinity.com/gv_w...i=46&co=1&vi=1

edit: What do you mean by interfacing with the LCD?

stevej88na

I just finished the less compact layout:



I'll check everything over in a while to make sure I didn't forget anything, and order a batch of these Monday. Along with eight analog inputs, this has two cellphone LCD outputs, so all eight signals can be seen at once easily. Two LCDs basically cover the entire area of the board.

stevej88na

The OctoLogger performed very nicely during a two-day endurance test at Laguna Seca. My friend let me test this on his slightly modified STi, and we logged X, Y, and Z accelerations, as well as air pressure at various points. I updated the how-to with a graph of the output from one lap:

http://howto.globalvicinity.com/gv_w...i=82&co=1&vi=1

The speed in MPH was calculated by integrating the forward Gs. You can see some interesting info there, like he's at his tires' limits laterally, but not during braking and acceleration.

My friend also agreed to start posting material relevant to SCCA and NASA racers in a new section called "Track/Racing" (he's the admin there now), so expect some info there in a few days.

fritts

iTrader: (5)

Do you have an boards of the less compact version built? If not when do you think you verify the boards and get some built. I think I would like to get one of the less compact boards if possible.

stevej88na

The less compact one (OctoLogger) is the one I tested at the track; I took the compact version down because I'm not going to make one myself.

dgeesaman

iTrader: (7)

Wow this is a neat project.

I've wanted to make a setup that splices into the FD's stock ECU (maybe use an old ECU and old wiring harness to make the plugs and wires), then tap into the signals I want. Maybe add a couple of old MAP sensors so I can peek into the stock sequential turbo control system during operation.

I got as far as figuring out which sensors I wanted to read, and what format the signal was in, but I lost steam designing the circuitry to safely isolate the signals.

I'm going to read your site and try to learn more, but if you have any comments about my plan that would be great too.

Dave