Hi folks

I've been busy and come up with a good way to install the second optoisolater needed for the CKP signal input on a Mk1, using the space that's free from not installing the VR circuit.

Instructions

1) Install the second 4n25 in the lower six pins of U7.
2) Jumper U7 pin 4 to pin 5
3) Jumper U7 pin 1 to pin 6
4) Install a 0.01 capacitor between U7 pin 6 and pin 5 or pin 4
5) Install a 470ohm resistor between the top hole of R44 and U7 pin 8
6) Install a 4k7ohm resistor between the left hole of R50 and U7 pin 8
7) Jumper the top hole of R52 to SPR1
8) Jumper VRout to JS10

Schematic





Please excuse the poor quality of the scan, but hopefully it's clear enough.

Nice and neat, and it saves you space in the proto area for other things.

 

you dont NEED the second opto.

looks similar to how i ended up doing it.





its a mess up under:

 

I know you don't need the second one, but I've had several people tell me that it's worth putting it in as a belt and braces solution.

It's that mess on the proto area that I'm trying to avoid, I figure that the space is there, might as well use it.

 

the opto circuit I'm running takes up little space...

I have two additional p2n222s for the Joe's spark output mod, and a input relay for my a/c switch, and the opto circuit, and a 100ohm resistor for the boost control mod.


let me map out what i did.

 

EVERY single NA I've built a Megasquirt 2 for, ALWAYS had problems with ramdom tach dropout without the second opto.

Yes, you ABSOLUTELY NEED the 2nd opto circuit for Megasquirt 2. If you randomly lose sync, this is your solution.

 

weird. never had the issue.

 

I'm just a neat freak when it comes to electronics, my experience is that if you make it neater then it's more likely to work first time and easier to troubleshoot if you need to.

 

no doubt. I did that spur of the moment, beforehand it looked great.

 

Here's a shot of how far I've got. I've also just realised that the 0.01uF capacitor can be fitted in place of R55.

 

interesting use of the spare space