New to EDIS 4 , don't quite get the wiring

[sammy]

Hi everyone
I’m trying to work out how I wire up Megasquirt with EDIS .
In the MS manual it has pin 7 shown as a shield. (http://www.megamanual.com/ms2/EDIS.htm)

On the EDIS connector there are 12 holes visible from underneath, but from the top (where the wires go in) there are only 11 and the place where pin 7 should go is blanked out.

Can anyone explain what is meant by pin 7 shield and are all EDIS4 like this or have i got the wrong one?
If not what do I need to do with this pin 7?

Also, I believe Pin 2 is originally intended as a diagnostic output that can also be used to provide a Tach signal.
but what about pins 11 and 4, do these do anything that I should care about?

thanks in advance
Sam


Thanks
Sam

[trakkies]

The 6 and 8 cylinder versions also use a 12 pin plug - although the key-ways are different so they can't be confused. So you need to use the correct wiring diagram.

However, pin 7 is the VR sensor/PIP SAW shield on all of them. It's possible one particular installation had wiring runs so short they didn't need a shield, and Ford saved 0.001 of a penny by omitting it.

I'd look for a plug with the terminal present.

Pin 2 can be used to to drive a tach - at least on EDIS8, as I use it, but it needs extra electronics for my rev counter as the signal level is too low. I'm not sure if it is connected on EDIS4

Pins 4 and 11 are not used on EDIS4.

[jcarruthers]

You can use pin 4 as your PIP/SAW shield for convenience— easier than using pin 7 for both VR and PIP/SAW.

[sammy]

Hi Everyone
Thanks for your responses.
I think I must be dumb because I haven’t understood all it yet.
I still don’t get what the purpose of the Shield wire is and where it connects to on the Megasquirt.
The EDIS-4 unit I got was from a roughly 11 year old Ford Mondeo Mk2? (Ford Contour in the US?)
The Part no is 91AB-12-K072-AA.

As you can see from the images (attached) , there is no place for a wire to connector 7.

Maybe Ford were trying to save a few cents, but I can’t help wondering what the purpose of the shield anyway and where it is meant to cponnect to on the MS anyway?

following are some questions I still have

1) Could the design have changed at some time and this version no longer needs a shield?
2) Would it hurt if I got a new plug wiht Pin 7 and used that with a sheild ?
3) Wires from Pins 1, 2 and 4 are all twisted together. (see images). I know 1 & 3 are the PIP & SAW, but what about 4?
4) Is pin 4 the shield for this particular model?
5) Where do the sheild wires connect to on the MS anyway ?
6) maybe ford decided that sheild 7 is nbot needed anyway?

Thanks in advance
Sam

P6230006.JPG

P6230005.JPG

[jcarruthers]

The shield doesn't go to anywhere on the MS— it should ONLY be connected at one end.

[trakkies]

The purpose of the shield or screen is to help prevent interference getting into - or being radiated by - a cable. Think TV co-ax - although in that case the screen also forms part of the circuit. With a VR sensor it doesn't carry the signal.

I'd definitely use screened cable for both the VR sensor and PIP and SAW. Simply connect the screen to chassis beside the EDIS ECU. Do not connect the other end to anything. Just tape it up etc to avoid the possibility of a short circuit.

[sammy]

'ting' .....(thats the sound of the penny dropping !)

jcarruthers / trakkies , your help is much appreciated.

The unit I got came with the wires cut.
I now realise there must have been a shield around the wires when it was on the car but not given to me when I bought the unit.

thanks for you help

Sam

[sammy]

folks
the EDIS 4 works great !

It fired first go and the car seems to be running smoother than before, even though haven’t got the MS completed and hooked up yet. (So it's just running at 10deg).

One problem I have however, is the Tach signal.
The old signal came off the Negative side of the coil, I tried connecting Pin 2 (IDM), but it no good.

So as per the Megamanual I will probably need to build the simple circuit described at the bottom of the link in the following link http://www.megamanual.com/ms2/EDIS.htm

Problem is that it mentions using the negative side of the coils.

So here is the dumb question, are the 2 wires coming from the coil packs to the EDIS 4 at pins 10 & 12 the negative side? Should I tap into these two?

Thanks in advance
Sam

[trakkies]

Yes - that's where the diodes go to.

[sammy]

Ok Folks,
I really tried but I still can’t get it to work.

As mentioned earlier, I have EDIS running in default mode (10deg), but I still can’t get the tachometer to work.

I tried the 3 diode circuit mentioned in the MegaManual.
I tapped into the negative wire from each coil, using the two 1n4004 diodes and the Zener diode, but no good.

I removed the Zener and tried again but still no good.

Then I tried just one wire from one coil to the tach (i.e. without any diodes)
And I worked ! (sort of … it only showed ½ the amount of revs as I only tapped into one coil).

Next I added the diode into that wire, and it stopped working.

From this I concluded that the diodes were faulty, i had a couple of other 1n4004 floating around, so I started back from the begining with these two without success.

I then went back to a single wire – no diodes and it worked (but tach shows ½ revs)

I introduced the new diode again and it stops working.

So I put a multi meter on the wire before the diode, I got the following
• 2.5 to 2.8 volts
• Idle around <.05 amps
• When revving the engine up to around 1.5 – 2.0 amps

I put a multi meter on the wire after the diode. I got the following
• 3.5 & 4.0 volts
• Idle around <.03 amps
• When revving the engine .05 amps

So now I’m totally confused.

I don’t have access to a scope so I’m trying to find someone who knows what the signal on the EDIS negative wire looks like and any ideas as to what the diode may be doing to it.

Thanks in advance
Sam

[trakkies]

Please don't take offence, but you are certain the diodes were the right way round?

I'd expect to see a spike of perhaps 50 volts or so when the coil is triggered, but a simple volt meter probably won't show anything like that. The diodes introduce a voltage drop of less than 1v.

I also had problems using the diodes circuit - my tach is quite an old design and likely needs a good kick to work. But in my case it did work - but not at high revs. I got round it by using an amplifier fed from pin2 on the EDIS8 unit - but intend fitting new electronics to the Tach movement. Eventually.

[sammy]

Hi Dave

It’s a fair question to ask.
Don’t worry it takes a lot for me to be offended, especially when I'm aware of my limitations as is the case here.

I wired the cathode end of the diode (the one with the band on it) towards the Tach and the Anode to the negative wire of one of the EDIS coils.

I did reverse the wire (and hence the diode) to test it the other way around but it didn’t seem to work.
Having said that, I did try a lot of things to get this to work and I can’t remember the sequence of events or if it didn;t work for some other reason, so I think the best bet is for me to try again tomorrow when I get home from work.

I’ll let you know how I go

Sam

[trakkies]

If the tach works from one EDIS coil (but obviously not showing the correct RPM) but not when you insert a diode, it might just be worth trying a schottky type.

[sammy]

Schottky ?
ok I'll see if I can get a couple tomorrow.
Let you know how i go

Sam

[sammy]

Tried the schottky, but NBG

However, I managed to get a Ford Mondeo Tachometer (same type of car I got the EDIS from).

So I pulled the tacho mechanism from the cluster, removed the face plate and discovered that the machanism is quite small.
It fits into the Alfas cluster so I made some brackets and swapped over the faceplate from the Alfa and installed it into the Alfa‘s cluster.

I wired it up and it seems to work ok.

Because the face place is from the original Alfa tacho, you can’t tell the difference.

Even though I have this solution, I would still like to understand why my old tacho didn’t work, even to help other folks who may have the same problem.

My friend is an electronics engineer.

He has reverse engineered the old tacho circuit board and drawn up a schematic diagram for me.

If I can get a copy of the EDIS internal schematic, he may be able to understand what the EDIS is putting out vs what the Alfa needs coming in.

This may help other folks too.

Does anyone have a copy of the schematic of the EDIS 4?
Sam.

[trakkies]

The other way is to replicate a coil firing from the dignostic output on the EDIS unit. The circuits I've seen involve a transistor feeding a coil - one from a car relay seems favourite. The back EMF is a spike of many volts which might just do the trick.
I've seen such a circuit here - but can't find it.

[Simple Simon]

Was it something like this

[trakkies]

Yes - that's the one. However, I didn't find it too successful with my Smith's unit which uses a variation of the 555 timer circuit. Playing with a 555, I found it very sensitive to the type of pulse it sees. So did some more research. I've ended up with this circuit driving the original Smith's moment. It is very tolerant of both the pulse shape and amplitude. Cheap to build too. Here it is:-



It works happily off IDM (pin2) on EDIS8. Note the circuit is just lifted from the LM2917 spec sheet - not my own work. ;-)

[Simple Simon]

Not seen that one driving the tacho correctly certainly can throw up a few problems

[trakkies]

Not seen that one driving the tacho correctly certainly can throw up a few problems

Yes. In my case more than the actual MS/EDIS installation. Other thing which stopped working properly was the OBC - the pulses MS sends to the injectors confused it, as it expected just switched DC. But that's now sorted too.