My max9924 board

[EssEss]

as promised to jared, here's the little board I layed out:




along w/gearheads recommendation of splitting up boards, here's how I usually do it:

Those are for my diy ecu in progress, I just etch all my own stuff. I hang screw terminals off the edge of the board and slap them down with some double sided tape on a board and start 'stitching' everything together. I didn't show the proc board on purpose since it's part of an existing product at work, but it's based on an lpc1766. any passives I need to lay down (decoupling/filtering/etc) are done on each board - I've had very good success. when I'm done and layout a final board all the little boards just go in a box and sometimes I pull them out for other projects or experimenting and kicking around new ideas.

critique away! it's not very complicated - I simply wanted to get something simple that works across all the zero-crossing modes .. mode C (which I didn't target in this board) is more for wheel/trans speed applications.

[jharvey]

I like the SMT. I don't see the typical points often left by an iron. Does that mean your sweet shop also has re-flow capabilities as well?

I'm curious, what tools did you use to lay this out. I don't recall the black background for schematic entry.

I see the 9926 claims it has internal precision trimmed resistors. I have to look closer at the 9924, I think I see those resistors as SMT on your board. If so, do the SMT's appear work well?

I'm also curious what you have tested it against. Do you have a test jig of some sort, perhaps a car you can play with for such testing? I know you have a nice scope, perhaps you have some scope traces to look at.

Thanks for posting.

[EssEss]

no reflow - I do it all by hand, I've done enough that I've got some pretty good hand-eye skillz everything on the board is 0603 which is the most common size I have laying around here in my junk bins. All my etching stuff is done with an iron and some special clay bubblejet printer paper - any defects are touched up w/a sharpie and then I etch w/ammonia pursulphate. my success rate has been 100% for about the last 5 years or so - I can go down to 10mil easy .. I've been toying w/8mil lately. it's all time intensive and certainly doesn't pay for itself if you put a $ figure on my time. as with everything else, I do it for the fun. I need to find a geek shirt like fred's

I use pcad for layout/entry - but they were gobbled up by altium a few years ago and I refuse to pay for a bloated piece of sh!t app. I plan on using pcad until I can't anymore. I'd really like to go back to the dos days of entry - that stuff was so snappy and just got the job done w/o all the fluff and gui eye candy. I started out on orcad 2, and cried the day I could no longer run it.

my testing has only been on the lathe, I have a bunch of patterned wheels of varying thickness and teeth I've cut on a waterjet that I use to eval my v/r circuits.

[Fred]

I started out on orcad 2, and cried the day I could no longer run it. :)

Having met you, I have a hard time imagining you crying. In fact, I guess if you were crying, I would have already soiled my pants! :-)

BTW, you can also bypass the shit filter with shlt ;-)

[EssEss]

haha! I'm pretty even tempered.

[jharvey]

About the etching, I've had some good luck running glossy bubble jet paper through a laser printer. Then flip, and reheat with an iron to transfer to the PCB. The laser jet ink will remelt, then detach from the inkjet paper, and reattach to the copper. The paper I get is often found in the dollar store.

Sounds like your paper is designed for a inkjet. If so what kind is it. I don't have a laser printer, I have to borrow a friends. I do have a couple inkjet printers.

Waterjet you say. I know a guy in PA that charged me a good price for some waterjet work. I'm guessing you had to pay for your parts as well, or do you have some other fat tools in your shop? You have a CNC, I've often wondered what would have happen to add a fish tank and a water pump to make a DIY waterjet.

About the VR, I'm curious what gap(s) between the wheel and sensor this chip can pickup. I might guess it works down to a gap of 0, and don't have a clue how large of a gap it can handle. I'd bet that's easy to take a measure with on the lathe. Any chance you happen to have that data?

[EssEss]

waterjet:
I have/had some connections @ the time to get free machine time in exchange for some testing of their toolpath s/w. this page might might give you a hint of what I did as my previous job: http://waterjets.org/index.php?option=c ... &Itemid=31 - the 360 at the bottom was straight off of my desk

v/r:
I test everything @ 2mm, but depending on thickness and profile it's pretty easy to go out to double that.

paper:
it was some old Cannon stuff that went out of production - I don't have a clue of anything comparable. As soon as I'm out, I'm done etching boards but @ my current rate, that will be a long time from now.

[Fred]

LOL @ the "X" box :-) Best use for them? ;-)