Joe, a pot would be good for minor tweaks, however that said, I don't think most people have access to a scope, let alone the experience to read it. <G>

oooooohhhhhhhhh pretty graphs.... <G>

Dave,

 

Ok, here is my contribution to the thread.

I've taken JasonC's original design and, while keeping all the same reference designators and the basic layout, added space for two multi-turn potentiometers. The idea is that those who have access to a scope should build the board with the two pots R20 and R21, but without R2, R10, R15 and R16. I'd suggest anywhere from a 20k to a 100k pot, depending on the magnitude of dwell reduction required.

Those who do not have a scope should omit the two pots, and install the four fixed resistors using known-good values. Apparently different year Miatae had different factory dwell, so over time I assume we'll be able to put together a table of appropriate resistor values. Additionally, I provided four mounting holes for 4-40 screws, so you can install this in an enclosure if you wish.

I've drawn the schematic and board layout in the ExpressPCB software. The advantage to doing this is that any of you can download my design, download and install the ExpressPCB application for free, and order your own board(s) directly.

The design is optimized to be ordered via their 2-layer "Standard" service. This will get you boards with a high-quality silkscreen and soldermask, just like a "Real" PCB. Basically, the same quality as you'd expect from a commercial circuit board.

There is obviously a huge savings to ordering multiple boards in one run, but I'm going to let someone who cares handle that. I'm not going to do the actual buying because I don't need one. Assuming that service is selected, here's how the cost will break down:

Qty 2 = $76 ($38 each)
Qty 4 = $83 ($20.75 each)
Qty 6 = $90 ($15 each)
Qty 8 = $96 ($12 each)
Qty 10 = $103 ($10.30 each)
Qty 12 = $110 ($9.17 each)
Qty 14 = $117 ($8.36 each)
Qty 16 = $124 ($7.75 each)
...and so on...


I strongly advise that someone should double-check my work before ordering anything, as quite frankly I'm tired and starting to see double.

Here are the schematic and layout in graphical form. The actual design files are attached as a ZIP.

 

Joe, add an NPN emitter follower to each output using a 2N3904 or 2N2222 NPN transistor. This way you can use a much more commonly available rail to rail CMOS opamp (MC30xxx, can't remember the p/n). Place it between the opamp output and the 100Ω resistor.

The delay is roughly inversely proportional to the value of the resistance across the diode. If you have a pot there, just place a small resistor in series to set the minimum R and don't bother with parallel resistors. The trouble with pots is their reliability - you have to use something like one of those Bournes blue and white plastic lay down types to get decent reliability.

Does your PCB software not check connectivity?

 

Any news?

 

Well I went ahead and added the BJTs I was talking about, and generated Gerbers.

See attached.

 

Jason
I would be willing to go into a buy, even if it's just the two of us. At the $38.00 level, it would still be worth it to me, but does'nt anyone else want to get the price down? Let us know.
Best always
Alden

 

Heh, $38 is like 15% of the way to a megasquirt. Think of all the little work arounds you have. And after you flesh out the board, it'll be more like 25%.

 

alden, I don't need to do a group buy
1- I don't need the circuit, I designed it for the miata community; I have an AEM
2- We have a machine at work that makes one-offs

 

I can offer the boards in a CNC box and sealed in epoxy. It changes alot when quantity goes up though, so if their is enough interest I can do a full solution not just a board. I would imagine minimum amount I could do would be 10. Below that the CNC shop won't do the enclosures.

 

I’m very impressed at you guy knowledge in electronics.

 

If anyone wants these complete plug and play I need 10 people interested, and unfortunately I'm a newb on the forums so you can't PM. Just post here, and letme know. I have a guy whose going to make the first couple for free so we can test out the boards. I don't have the equipment to test them and we would need someone to do the test part as well to make sure the larger run is going to go ok. I only have one person interested so far, and we could have the test boards by next wed if there is enough interest.

 

I'm still not sure how this works but, put me in your group buy.

 

Add my name to the list as well.

 

Alright, I've got three people all total haha. I haven't heard back on the status of the test boards yet, but they should be arriving this week. I'll let you all know how it goes.

 

Did you use my newer version with the transistor on the output?

 

POPSTOY4WBJT_Gerber.ZIP (43.3 KB, 14 views)


Jason,

Yea I used this Gerber, I didn't see mounting holes on the boards. Which gerber file are the holes located in? Also, do you have any idea on where I can find some adapter that would fit or I could rig to fit the stock connector so people could simply plug and play. I have been searching digi key for a while now and have come up blank.

Travis

 

Hmm, I didn't put mounting holes in. I could ...

 

If you could put them at the corners that would be great. I can view the gerbers but can't edit. Besides gerbers look alot like autocad which to solid works users who are used to parametric solvers represents an unholy and evil entity. I don't want to do anything against my beliefs.

T

 

Alright guys somehow the signals got crossed on how many I wanted on the first batch, and I think I'm getting about 40 of these PCB's. I'll have to see about cost. If you don't want them assembled i can pass them on for pretty cheap. If you want them assembled... Well they'll still be pretty cheap. If you want them in a pretty box, with connectors and plug & play you'll have to wait a bit longer & pay a bit more. I still haven't found an easy way to hack the adapter. Visit my website and pop me an email in the contact section if you want in on this. I'm out of town right now and can't respond to email, or setup the webpage to have an official order spot or anything. www.boundaryengineering.com

Also no serious obligations here until we find it does work perfectly I just want a number interested so I can get a quote on the first batch assembled. I can't test this part and I don't even need a convertor as I have an adjustable dwell standalone. These are just for you guys! Can someone with the know how and the time to test Jason's work plz plz send me an email so we can get these boards certified as a working part. I really don't want to ship these until we know for sure.

T

 

Quote:If you want them assembled... Well they'll still be pretty cheap. If you want them in a pretty box, with connectors and plug & play you'll have to wait a bit longer & pay a bit more. I still haven't found an easy way to hack the adapter.

TravisR this site has a lot that may help. I got my pretty box here.
http://www.bgmicro.com/index.asp?Pag...S&Category=316

I bought all my stuff here and at digi-key.
Hope this helps. I trying to build the first edition PCB and dwell device.

Lee