schoolproject megajolt inside

Polleke · Post by **Polleke** » Sun Feb 03, 2008 6:15 pm

Hi ,Im building a testbench for megajolt for a schoolproject in Belgium.
http://www.autosportlabs.net/User_talk:Polleke
Now ,can anyone explain to me how the internals of megajolt work ?
I know about pip and saw and how to configure and connect the whole lot.
I will have to explain the electronic part of megajolt to a group of teachers.
Please can anyone help?

Cheers
Polleke

Post by **brentp** » Sun Feb 03, 2008 6:54 pm

Welcome Polleke,

You did a very nice job on your test bench!

Here is a basic description of how the MJLJ works:

1. The MJLJ receives the PIP signal
2. The MJLJ Calculates the current RPM based on the period between PIP signals
3. The MJLJ measures the load (MAP sensor or TPS)
4. The MJLJ finds the proper ignition advance in the Ignition MAP table based on the measured RPM and load.
5. The MJLJ calculates the proper SAW message pulse and emits this to the EDIS module.

Schematics and firmware source code can be downloaded from our wiki for your reference.

I hope this helps!

Polleke · Post by **Polleke** » Sun Feb 03, 2008 7:09 pm

Hi Brent thank you for the quick reply .
I would like to know more about what's happening inside the IC's.

Polleke

Post by **brentp** » Sun Feb 03, 2008 8:16 pm

Ok.

U1 is the microcontroller that runs the firmware program outlined in the steps above.
IC1 is a transistor array that drives the "user defined outputs"
IC2 is the RS232 transceiver, which interfaces the microcontroller with the RS232 serial port, which connects the MJLJ to the PC.
U3 is the +5v voltage regulator, part of the power supply circuit.
QG1 is the oscillator which drives the clock for the microcontroller.

Hope this helps!

Polleke · Post by **Polleke** » Sun Feb 03, 2008 8:51 pm

Cheers Brent,this helps a lot.
Any chance of some more info about the µcontroller?
I'm afraid that my teachers are gone ask me what's happening inside the µcontroller.

You see,I found a lot of info about EDIS and I suspect that they want the same kind of info for the megajolt part.

Thanks
Polleke

Post by **brentp** » Mon Feb 04, 2008 3:03 am

As before, the microcontroller runs the firmware code, outlined in the steps above. Is there something specific you are interested in?

You are free to download and browse the firmware source code, it's well documented. If you'd like to understand more about microcontrollers in general, there are some excellent articles out there, including some good wikipedia entries.

Gilesy998 · Post by **Gilesy998** » Mon Feb 04, 2008 8:28 am

I'm afraid I can't offer any more information than has already been given, but I'd like to say that your test bench is inspired! I love the use of the drill speed reg to vary the grinder's speed and the general overall presentation - good work!

Polleke · Post by **Polleke** » Mon Feb 04, 2008 3:13 pm

well Brent on the site of autosport labs you find a lot off info about the megajolt module.
This site has been verry usefull untill now but I'm following elektronics on my shool and my teatchers will also be interested in how the megajolt module works eletronical

do you have a link on the site where this is explained
this would be very usefull

thanks Polleke

Polleke · Post by **Polleke** » Mon Feb 04, 2008 9:05 pm

Hi,sorry for not replying earlier
Just had a harddrive faillure on our main computer.

Thanks a lot for all the info
I gues I will have to get myself some more information about microprocessors and especially the MC908kX8CPE.
Any site that comes recommanded?

Polleke

Post by **brentp** » Mon Feb 04, 2008 9:15 pm

Hi Polleke,

You can download the schematics and firmware source code here:
http://www.autosportlabs.net/MJLJ_V3_Downloads

A great write up on microcontrollers in general can be found here:
http://en.wikipedia.org/wiki/Microcontroller

You can find this controller's datasheet here:
http://www.datasheetarchive.com/68HC908 ... sheet.html

Best of luck in your project!

Polleke · Post by **Polleke** » Mon Feb 04, 2008 9:44 pm

Thank you for the links and all other info Brent
I'm sure that your info will keep me busy

Polleke

Yvan · Post by **Yvan** » Thu Feb 14, 2008 7:53 am

brentp wrote: IC1 is a transistor array that drives the "user defined outputs"

Does this mean that if I do not need "user defined outputs", I can omit completely ULN2003AN?

I am asking this because I want to make Air/Fuel Ratio controll unit to controll LPG/air mixture for my car.

I have very basic electronic knowledge, but I am willing to learn, and there is a lot of info at the Internet, and a lot of nice people at forums and newsgroups that can help.

Or perhaps I can add this function to the MJLJ? It already has load input (MAP or TPS), it just needs feed from O2 sensor and stepper motor driver for mixture controll.

Of course I am not talking here about LPG injection systems, but older simpler carburettor engines.

MartinM · Post by **MartinM** » Thu Feb 14, 2008 10:36 am

You can certainly run a MJLJ without the ULN2003A 7-way driver present if you don't want any of the outputs that it drives - PGM1 to 4, the rev limit signal and the shift light signal (and I just noticed it has a spare driver inside it - that might be interesting one day!)

Turning a MJLJ into a dedicated A/F ratio controller or adding A/F ratio controlling to a MJLJ (whilst retaining all its current iginition capabilities) sounds pretty easy if:
- you are a competent analogue electronics engineer and know exactly how to interface a lambda sensor with the MJLJ electronics
- you are a competent digital electronics engineer and know exactly how to interface a stepper motor with the MJLJ electronics
- you are a very competent software engineer so that you can rewrite completely/highly modify the MJLJ software to take a lambda sensor output and transform it into a stepper motor position (and you have the development tools and suitable programming hardware available)

But it would be a very clever project!

Yvan · Post by **Yvan** » Thu Feb 14, 2008 5:09 pm

As I wrote I am not an expert in any of the fields you mentioned, I am asking this here only to see if it might be something easy to do, but it looks it is not.

What I know is that narrow O2 sensor gives output 0-1V depending of A/F ratio, that we already have MAP readings (and can easily get TPS readings), and that you can find a schematics on the Internet for stepper motor driver (like this one that uses ULN2003 not essential for MJLJ - http://www.avrprojects.net/articles.php?lng=en&pg=64 ).

Add few lines of programing - A/F ratio controller finished

I am just kidding, of course. I posted this hoping that someone will see this, and reply: "This already exists, check here: www.something.com/a-f-controller". I might have to buy finished product, but I prefer something that I build, and configured...