Prototyping board for SOIC and DIP

[barnacle]

I dislike the plug-in prototyping boards a la Ben Eater and some other youtube sources... I've spent most of the last couple of days fighting intermittent contacts (and the same every time I've used the damn things in the last forty years). It's probably safe to say that I'm not a fan. One other thing that has annoyed me is the difficulty of using surface mount parts, if that's what you've got in hand; ordering a handful of chips from any of the big four is simply not economical, when the postage can significantly exceed the cost of the parts.

So I bodged up a solderable prototyping board... it can take either SOIC or DIP parts in 14, 16, or 20 pin packages; the spacing is such that larger DIP parts will fit if the places are selected. A total of 3 * 14, 18* 16, and 10 * 20 pins (and of course you can place smaller parts in larger places. It has vertical power rails like the plug-in boards, but these are hard-wired together; there are also places between each IC where an 0603 decoupling cap can be placed (these are not permanently attached to the rails since that would break the positioning of larger chips. SOIC 24-28-32 would have to go on their own adapter to DIP 32. I'm thinking 0.8mm to keep the postage down!

JLC are quoting me about fifteen bucks for five, which at 160x190mm strikes me as a bargain. I'm just about to order some. I anyone wants the gerbers, let me know.

Neil

[BigDumbDinosaur]

barnacle wrote:

JLC are quoting me about fifteen bucks for five, which at 160x190mm strikes me as a bargain. I'm just about to order some. I anyone wants the gerbers, let me know.

Is that image of a single board, or is it a bunch of them panelized?

[barnacle]

That's a single board, about equivalent to four or five of the plug-in boards side by side in capacity, but a bit narrower (there are more power rails in the plug-ins).

Neil

[Dr Jefyll]

Very nice, Neil! (And here's that same image, but with better visibility of the fine traces.)

barnacle wrote:

intermittent contacts (and the same every time I've used the damn things in the last forty years)

Solderless breadboards do seem to have a bad reputation in this regard. And it's easy to believe a breadboard with intermittent contacts will eventually exhaust one's patience and lead to defenestration of the offending item.

That said, it would probably be a mistake to paint them all with the same brush. IOW, I suspect the quality varies widely from one brand to another. I have limited experience with solderless breadboards, myself. But, acting on Radical Brad's advice, I chose to purchase Twin Industries' breadboards, and -- so far, at least -- my blood pressure and cheerful disposition have suffered no ill effects.

(But they're still no substitute for your protoboard, as they don't accommodate SMT.)

-- Jeff

[BigDumbDinosaur]

Dr Jefyll wrote:

...my blood pressure and cheerful disposition...

Uh-huh.   

[BigDumbDinosaur]

Speaking of proto PCBs, some years ago (about 15, to be exact), I came up with a proto PCB to plug into the cartridge slot on a C-64 or C-128.  I never followed through with it, as I ceased monkeying with those computers shortly thereafter (however, I still have my C-128D and Lt. Kernal).

Commodore 64/128 Expansion Port Proto PCB

[barnacle]

One of the nice things about the Microtan 65 system was a backplane (after the first two boards) which expected a DIN Eurocard (100x160mm) with a DIN 41612 connector - 2*32 pins, A-C IIRC. And they were dead easy to get as protocards; Vero did lots and a quick look tells me many similar are still available, like this one: https://www.newark.com/multicomp-pro/mp ... p/40AJ7666

Neil

[barnacle]

Yay, the boards are back (and also a SOIC-28 to DIP adaptor). 0.8mm feels a little flimsy, next time I'll do 1.6mm.

Neil

[barnacle]

I built the timing for my DMA design, and amazingly, it worked. Though I just realised that though I fitted the decoupling capacitors, I forgot to wire them to the rails...

These are an odd frequency - the oscillator is a random baud rate generator at 14.7MHz or so, instead of the final 20MHz. Everything's referred to the final phase0 (yellow).

This is the load enable for the '166 - there's a rising clock in the middle of that which I haven't wired yet.

Here's the async clock AKA BE signal; when it's low the video circuit has the bus.

Things I'll change for the next version:

• Make it in 1.6mm to make it a bit heavier; it skates around the desk at present.
• Draw some outlines on the back to make it easier to see where the parts are
• Possibly add a voltage regulator - 5v to 3v3. Not sure if that's an issue yet. It would also give a possibility of including a reverse voltage protection diode.

Neil

[GARTHWILSON]

barnacle wrote:

0.8mm feels a little flimsy. Next time I'll do 1.6mm.

For work, I always make the small boards 0.8mm (.032") thick, and it's never a problem.  We have a lot of boards that are not much bigger than a postage stamp.  Here's one, 1" long:

[barnacle]

Yeah, the SOIC-28 adaptors feel fine. But the breadboard is approx six inches by eight.

Also, it's amazing how much better it gets when you remember to wire in the decouplers: 100nF between each chip.

Neil

[barnacle]

Well, having found time to build something between all the hassle of moving house, I think I've proved out the proto board. At the moment, this is just an SVGA video sync pulse and timing generator, with a mix of SOIC and DIP parts depending what I had on my shelf. For easy identification, all connecting wires are blue...

I'm contemplating adding spaces for some sockets on the next version - maybe generic DB-9 and DB-15 (vga) - but before that I may extend this to include a processor, ram and rom. It won't do the full 'half an idea' circuit because there's no space for an LQFP, and I really don't want to go that way, for that way lies madness.

But: it's convenient to use both packet types; soldering is easy (much easier than e.g. veroboard); and there's room for a lot of chips on the board. The decoupling capacitors are extremely useful in keeping the signal sane; I'm using a 20MHz clock on this board, and I think I'll double that next time I make a parts order.

Neil

[plasmo]

You can fit a pcb mount VGA connector in 3x5 grids by bending middle row pins of the VGA connector to line up with other two rows. It takes a few adjustments to line them up correctly, but the result is a sturdy pcb-mounted connector good for many insertions.
Bill

[barnacle]

Yes, but sadly there isn't a place on the current board - because of the four or five pin tracks - where it wouldn't be shorted between pins. The same would apply to a DB-9. Though to be honest, I think a DB-9 would be less useful.

Neil

[BigDumbDinosaur]

barnacle wrote:

For easy identification, all connecting wires are blue...

There are actually wires on the board?    Could’ve fooled me!