ezk Daughter Board Schematic and prototype. Need your help

[Scodfish]

Three weeks of my life, two burned up computers, one prototype board with schematic. Priceless.

HarrieCo (gone) and other boards are getting harder to consistently acquire, so I’m trying to make this open source. Get the file order and or assemble your own. I have taken the time to reverse engineer and older board and made a working prototype. I am looking for someone who can build a circuit board file. (Gerber?) The physical layout can be modernized using smd components but this complicates manual assembly. I would also use a 28 pin socket with a built in bypass capacitor. I have learned many factor that affect the performance of this board, but it is basically a Heathkit project.




Enjoy!
Justin

 

[nalletill1000]

EasyEDA is your SW (free) and send it to JLCPCB and get a ton of them for next to nothing. I can help of you don't feel like dabble with it.

 

[bobxyz]

This would be a great project to do with EasyEDA. EasyEDA.com is one of three websites run by the same Chinese PCB manufacturer. https://easyeda.com/ has free web-based tools to layout a PCB, then have it fabricated by https://jlcpcb.com/, and optionally assembled with parts from https://www.lcsc.com/.

Un-assembled boards are shockingly cheap, and nice quality. If you go to https://jlcpcb.com/ , click on the "Get Instant Quote" button, under Dimensions, enter 65mm x 30mm, and set the quantity to 50. Leave the rest at the default values. The price for 50 boards is $14.70 and shipping is $30. 2 week turnaround, or a bit faster, is standard.

They offer assembled boards too, but you need to use parts that they have in stock, and there are small extra fees if it's not a very common part, or if it needs non-SMT assembly steps (e.g. through hole wave or hand soldered). There's often discount coupons available that makes even the assembled board amazing cheap. Finding suitable and available parts takes some practice - it's no where near as nice as digikey.

For the EZK daughter board, you can get machined-pin sockets for ~$0.50 each, plus assy charges - try either: link1 or link2. It may take some digging to find the right-angle 0.1" header in the correct length - you might need to do this by hand. For the board itself, try to keep the design similar to the original Bosch board, but with single-sided components. Some of the aftermarket boards stick out too far and need careful assembly of the right angle header to avoid shorting into the main board IC next to it.

Feel free to post follow up questions as you navigate the process. Once you've made it through for the first time, you'll never make a board by hand again.

 

[Scodfish]

Yeah no, you nailed it.. I have made it as far as I can. I've got the design in my head, just not going to be able to put it on a computer.
This is how far I made it. I also tried a few others. I'm a hands on type of person. You can tell by the hours of dremel work. Just remove anything that's not the trace.. This software just reinforced my belief.

 

[90volvo]

Yeah no, you nailed it.. I have made it as far as I can. I've got the design in my head, just not going to be able to put it on a computer.
This is how far I made it. I also tried a few others. I'm a hands on type of person. You can tell by the hours of dremel work. Just remove anything that's not the trace.. This software just reinforced my belief.

View attachment 38151

same here, 10 yrs ago I was afraid of wiring and soldering etc. But after microsquirt converstion, Im learning but cant picture my self doing this but who knows, if I cant sleep will be a good late night dive.

 

[nalletill1000]

I don't know how big the board you're designing is, but if you can it is possible put multiple boards into the designed board you're sending in if it all fits within the 100mmX100mm and thus cut the cost further. If spaced properly it will be scored so you can just snap them apart, which is very satisfying to do, like popping bubble wrap bubbles.

 

[Scodfish]

Hey, thanks you for the advice so far. I went to get a second board and found out I only had two options overseas maybe and Redblockpowered was having delays with his. So I did what any insane person would do. Looked at pictures on the internet, research the chips operation. Drilled, Dremeled, soldered, Tested, fixed, tested, fixed.. I only wanted one for my car. A more production one would be nice. I was thinking the working schematic would be the hard part but hit a road block with the software. The board is aprox. 75x30mm. I don't know how well you know the software or how long it would take to draw up a 2 layer through hole board. I don't believe these are in production anymore. This is what I was referencing for basic layout. This design needs some updating. Let me know what ya think.

 

[nalletill1000]

Hey, thanks you for the advice so far. I went to get a second board and found out I only had two options overseas maybe and Redblockpowered was having delays with his. So I did what any insane person would do. Looked at pictures on the internet, research the chips operation. Drilled, Dremeled, soldered, Tested, fixed, tested, fixed.. I only wanted one for my car. A more production one would be nice. I was thinking the working schematic would be the hard part but hit a road block with the software. The board is aprox. 75x30mm. I don't know how well you know the software or how long it would take to draw up a 2 layer through hole board. I don't believe these are in production anymore. This is what I was referencing for basic layout. This design needs some updating. Let me know what ya think.

View attachment 38225View attachment 38226

What is the problem with the software? It takes a little while to get used to at first and it is a bit quirky. I have made a lot of stuff with it. Do you have the pitch/foot print of all the parts? It should not take me too long, however, my schedule is packed the next week.

 

[bobxyz]

I went ahead and drew up some schematics and laid out a PCB at JLCPCB. I added a DIP switch to allow selection between 4 different tunes (the EPROM is 32KB in size but the EZK firmware only uses 8KB). Rough pricing when ordering 25 fully assembled boards is ~$4 per board, and DHL shipping is ~$25.



Can someone review the schematics (attached) and see if you spot any problems?

If it all looks good, I'll post the files needed by JLCPCB to make&assemble the boards.

 

[crogthomas]

Just a thought. It would be useful to add a couple of through holes for power to allow a wasted spark board to be wired in a bit easier. We'd still have to take our chances with the other leads, but the power supply might be a bit more reliable.

 

[bobxyz]

I've reviewed the PCB files and I think they're good to go. +5V and GND holes added for easier wasted spark setups. I'll probably order some boards in the next couple weeks (along with some boards for a different project). If you want to try getting boards before then, please post a note so only one person is taking the 1st prototype risk.



See the attached .zip file for instructions and all the files needed to get boards built and assembled by jlcpcb.com.

 

[crogthomas]

Nice, but I had another thought...
Is it worth making sure there is clearance around the EPROM socket for a ZIF socket to be pushed into the socket, to allow easy chip changes whilst tuning? That surface mount 74 series chip is probably low enough for clearance, but are there published dimensions?

 

[pinguin]

I'm dumb. Ignore.

 

[Led]

It would be awesome if the tune selection switch could be mounted externally.

 

[bobxyz]

Can a ZIF socket fit?
I think there's enough clearance but low cost ZIF sockets have oversized pins that won't fit the daughterboard socket. To get around this, you can solder a separate round-pin socket onto the bottom of the ZIF socket, which makes it taller, but it will then fit the daugherboard socket. Any ZIF socket with a PROM installed will stick out too far to re-install the back cover of the EZK box.

'207 gold box with factory daughterboard, added low cost ZIF socket, and Ostrich plug/cable:



Can external bank select switches be used?
The problem is that the bank select wires are not protected from static electricity, which is a real concern with the EZK being mounted directly above the passenger-side carpet.

SW1, the internal/external code switch, goes directly to the EZK processor chip. If it gets zapped, the EZK box may be dead.

SW2 and SW3 are the bank select switches, and go only to the EPROM chip. If they get zapped, the EPROM may be damaged, but it can be replaced.

You can probably get away with un-soldering the DIP switch, adding a jumper across the SW1 PCB holes, and adding short wires to extend the DIP switch (just SW2 and SW3) outside the EZK box. When I say short wires, I'm thinking 3" or 4", certainly not feet. Using a shielded 3-wire cable, with the shield tied to ground at the DIPswitch pads, is a little more robust than 3 individual wires.

A better, but not as convenient, alternative is to drill a ~3/4" hole in the EZK plastic cover in front of the DIP switch. When the EZK box is mounted, the hole would be facing downwards, but the switches would be accessible and visible using a mirror.

The switches should only be changed when the ignition key is off. Changing switches with the engine running will glitch the EZK code, which could cause engine damage in the worst case.

 

[Swedbrick]

It appears I've lost the schematics for the final version of my board, but it's simple enough that the Gerber render itself should allow you to figure out how it's wired. The chip is a SMD version of the 74HC573, and for the header I recommend mil spec headers with a decoupling cap across.

I still have a batch of a 100 to be build, but I now just occasionally help out friends. Cameron should also have his boards ready soon.