DFH - Defacto FreeEMS Hardware in KICAD

[jharvey]

I disagree to an extent. It's easier for me to get SMD then it is to get thru hole. However I already have much of the thru hole parts, and I don't see why I can't simply allow SMD and thru hole.

I've made hybrid SMD and thru hole footprints for resistors and diodes. I'm currently looking at combining the DPAK2 and the TO220 package. I plan on making stab at caps as well in the near future. I don't think it's a big deal to allow for both.

[Brian]

I've made hybrid SMD and thru hole footprints for resistors and diodes. I'm currently looking at combining the DPAK2 and the TO220 package. I plan on making stab at caps as well in the near future. I don't think it's a big deal to allow for both.

As in, the SMD footprint will be underneath a through-hole resistor for example, so no PCB real estate is lost, but the builder has a choice of SMD or through-hole?

Brian.

[GrowlingandBiffo]

For all DIY and prototypes use Plated Though Hole.

This system work well for years and still does.

Surface Mount Devices were developed to reduce automated assembly time/costs and the size of the PCB, so as you all have lots of time and indeed room it will matter not.

Suggest stick to Lowest Common Denominator and include all.

Any one whom is brilliant at SMD work, will be able to manage PTH.

Get it all up and limping first before you go the V357 route and lose the prototype area...

Keep up the good work one and all...you are impressing many...

[Fred]

As in, the SMD footprint will be underneath a through-hole resistor for example, so no PCB real estate is lost, but the builder has a choice of SMD or through-hole?

Yes, that is correct. I think/thought it is/was a good idea, but a few people disagree. I'm no longer certain, but I can only see SMD guys being against it because they loose the same space as TH guys do with this method.

Fred.

[jharvey]

As in, the SMD footprint will be underneath a through-hole resistor for example, so no PCB real estate is lost, but the builder has a choice of SMD or through-hole?

check here for a quick picture of the idea.

http://www.diyefi.org/forum/viewtopic.p ... ead#unread

I've already change my mind about it a pinch. I think I want to offset the 0805 so that silk screen can still go under the device. Right now with it centered, you can not silk screen either side. I'd like to put "2.2k" under the device, to help aid in assembly.

I like SMD because it's easy, quick, and allows me to etch my own boards with minimal drilling. I agree that thru hole has it's place, so hybrid is my goal.

[Fred]

I like SMD because it's easy, quick, and allows me to etch my own boards with minimal drilling. I agree that thru hole has it's place, so hybrid is my goal.

I've been thinking about that, and I think provided the SMD guys aren't anti it enough to not buy in on a purchase of some boards then it is a goer as it could mean more people want the same board at this stage.

Doing 2 PCB designs is possible too, but we'd need twice the buyers for that, so that probably rules it out.

Good move on offsetting the SMD part to enable a silk screen. I think it's important to at least have R23 etc on a part so you can look it up even if you don't have room for the value too.

Fred.

[jharvey]

I'll have to learn a bit more about this. My intention is to have R10 (or similar) next to the component, such that it can always be seen, and traced back to the schematic. I was then going to put the expected value under the component such that when populated with thru hole, you wouldn't be able to read it.

Looks like my current draft of the foot print doesn't do it that way, I'll try to do a better on the next go at it.

[Brian]

It is unlikely that a run of 10 PCB's would cost even $150, so $15 each, whether it be TH or SMD. That is for a 2 layer board. I don't think that is expensive. 20 boards of one type would cost around $10 each max.

For those who etch their own PCB's, they are still going to have to drill at least 150+ holes, 100 for the two headers alone. Might be easier/better to pay the $15 (plus postage) and get a solder mask, screen print and all holes drilled and plated.

It's not out of the question to do a SMD PCB and a TH PCB. A hybrid board sounds odd to me, but maybe that's just me. With all the extra pads or holes, it would make the PCB easier to modify if some part of the cct didn't work quite right. On the other hand, it might not make the TH people or the SMD people happy. I would think the later designs will not be hybrid, so would it be better to just do a PCB for both versions right from the start? If it has to get down to one or the other, my vote is for TH.

[jharvey]

I'm tempted to do another release, but the changes are reasonably minor, at least pictorially, they are minor. Mostly back end stuff to help make the netlist. If anyone would like a release, I'm willing, but until I get more done I'm planning on holding out for a bit more. I mostly wanted to release to get a copy of the foot prints out there.

Here's a snap shot of the foot prints I've created.



Still looking to figure out what footprints I need for caps, and other components.

I agree that the reg should be TO220, at least for this run. I suspect it might not get as hot as we are expecting, and perhaps SMD can be done. Heat sink across the top of the device of course.

I planing on making a footprint for the TO220 that will allow for via mounting as well as on it's back, hanging off the edge of the PCB. If we do it this way, we can keep easy flat mounting, and remove the need for bending leads.

[Fred]

For those who etch their own PCB's, they are still going to have to drill at least 150+ holes, 100 for the two headers alone. Might be easier/better to pay the $15 (plus postage) and get a solder mask, screen print and all holes drilled and plated.

I hadn't considered that. It would definitely be a major PITA to do that. Plated holes are well worth the effort IMO. They make for a very secure joint. It's important that the first solution fits everyone well enough. We just don't have enough people yet to split over two setups unless multiple people are looking to buy multiple boards in the hope of passing them on at a later date.

I suspect it might not get as hot as we are expecting, and perhaps SMD can be done. Heat sink across the top of the device of course.

Maybe with a top mount heatsink, but those are semi dodgy at least. There definitely will be a significant amount of heat from a linear reg dropping 10V at 0.5A, 5 Watts to be precise :-) With sinking, no worries, without, it will overheat very very quickly and self protect. I know this for a fact. Even the sinks you see in my picture get pretty toasty and they are fairly decent for single to220 sinks.

Fred.