Automated Circuit Production

Hey,

Check out this article i wrote about potential methods for using RepRap to automatically fabricate circuits. I'd love to hear your feedback, especially about things that may or may not be possible.

[reprap.org]

~Zach

LOL! You know, this who thing about making RepRap make circuit boards and wiring wouldn't be nearly the issue that it is if you all had designed a simpler control scheme at the onset. There are SO many things that a RepRap can be used to make that would make the world a better place that I really wonder about this obsessive focus on making circuitry that the team seems to have got into.

I've wondered and wondered about this. I've wondered as well if why you've settled for a bunch of little boards in a serial loop isn't being driven by the fact that it is so hard to get the SDCC compiler to work with any PIC, much less the 16F628A. Has anybody programmed a chip besides the 16F628A with SDCC or a chip like the 16F648 that is just a 16F628A with more memory?

Has anybody tried, for example, a 16F877A with SDCC? I'm not suggesting that you do, but is it even possible without the sort of pain and suffering that you all have reported with trying to build a SDCC app that avoids the broken bits that you report creep in every time somebody on the SDCC team tries to "fix" something?

I just can't help wondering if you all have let a very small tail wag a very large dog here.

That seems to cover all the bases Zach - can you add it as a link from the Mendel-in-the-future page?

---

best wishes

Adrian

[reprap.org]
[reprapltd.com]

Actually Forrest, the control design we have is the simplest possible, in that it doesn't get any more complicated as the machine gets more complicated. A single controller is a dead end.

heres the thing:

this isnt just about reprap making its own boards. its about it making any circuit board you can dream up. yes, it will definitely need to make its own boards, but this project is only about self-replication on the surface.

what it is really about is creating a general purpose machine that can create amazing objects from a variety of materials with as little external input as possible. we want to create a tool that other people can use to make really cool things. in order for that to happen, it definitely needs some way to ease the process of custom electronics creation.

that being said, how do you support a machine with 3 axes + 1 turntable + 5 deposition heads + tool changer, etc with a single board? answer: its really hard. i know you're trying the 'experimental' way, but dont get too far off track that you become your own project.

We'll see.

***this isnt just about reprap making its own boards. its about it making any circuit board you can dream up. yes, it will definitely need to make its own boards, but this project is only about self-replication on the surface.***

Um ... yeah, but how many people out there in the Third World are going to want to design circuit boards and how many are going to want to design three dimensional objects that they can actually use. You know, those bowls, coathangers, little plastic bits that go in drip irrigation systems and the like that RepRap used to talk about as being so important.

Mind, I can see the sense of wanting to have integral wiring. Just looking at the notion of a more or less all plastic reprap and then taking a quick glance of the mare's nest of comms and power wires in Tommelise that need to be sorted into a wiring harness is easy evidence of that. We can do that with metal impregnated polymers if nothing else. This emphasis on circuit board fabrication, though, that baffles me. I'd have thought that simply buying off-the-shelf or making a circuit board blank out of copper foil and a higher temperature plastic like HPP and then strapping it on the XY positioning table with a little router/drill Dremel or similar to tap the holes and get rid of excess copper would have been enough. I can certainly do that with Tommelise.

***that being said, how do you support a machine with 3 axes + 1 turntable + 5 deposition heads + tool changer, etc with a single board? answer: its really hard.***

I'm a lot closer to having done that than anybody here. I can say it ain't that hard. If you take a look at the Tommelise controller board it has two dual Darlington chips, a PIC and a power transistor on it. The most numerous item on the board is screw connectors to bring in signals from limits sensors and shaft encoders. I'm nowhere near the top of the CPU power, A/D channels or I/O ports capacity of PIC's, never mind a half a dozen of their competitor's lines. About the only thing I have to worry about is shifting from a DIP socket for PICS to something that can handle more pinouts. They don't make DIP's much bigger than 40 pins.

***i know you're trying the 'experimental' way, but dont get too far off track that you become your own project.***

I expect that that has already happened, sadly. I don't feel like I'm the one that's got off-track though.

Let me pose the question that didn't get answered AGAIN, though. CAN you compile programmes for a chip besides the PIC 16F628A and it's twins save having more memory like the 16F648 using SDCC?

Edited 1 time(s). Last edit at 02/23/2007 11:57AM by Forrest Higgs.

Yes, we can compile for any of the PIC range. We have already talked about possibly switching to the 16F648. The PIC16 (ie PIC18*) series compiler is also more complete and powerful than the PIC14 Iie PIC16*) series.

Glad to hear that.

I'm all for a simple board, repeated around the place. Better opportunity for useful spares...

Actually, we will need to print a PCB in Mendel. So it seems that a process for making printable models of circuits isn;t a bad idea. Using them to print resist masks on copper PCBs could be viewed as an adjunct to that.

Vik :v)

No one has touched this thread in a while - but I hope I can get some comment anyway. I'm brand new to the project and I have just started... Probably a bad idea - but I've started with trying to make the boards (I don't have my linux system up and running yet to play with software - but I'm working on it). My first thought on the system is this. Why not use a breadboard to make the circuits? I found a cheap one and I'm getting ready to build using it. This also gave me a second thought: wouldn't breadboards be something really easy for the machine to print (I mean the plastic part - there would be assembly necessary to add the connections internally).

Now, I'll add a bit more justification. First, it is much easier to assemble on a breadboard then to etch or cut a circuit board. Secondly, this allows more prototyping in the community - if you have an idea for a change, just try it out! Finally, it increases the reusability of all of our parts in the system. Since the focus is on experimentation and accessibility I think these should be compelling arguments.

When I have a completed circuit I'll e-mail pictures to the list. What would help me most is some circuit diagrams - I'm having a hard time finding them. Any pointers? Is there a reason you aren't going in this direction? I'd love to hear your thoughts and I'm going to need a lot of help if I'm going to get things working! I love the project and I really admire all of the effort you have made so far. I just hope I can get to a point where I can help!

hey corey, thanks for your interest. actually, our circuit boards are in pretty decent shape, and they are pretty stable (in that they are tested and the schematic isnt going to change for a while)

if you're interested in the experimentation side, by all means go ahead and assemble it on a breadboard. if you want to work on the circuits, you should DEFINITELY install kicad. it had all the circuit diagrams, pcb traces, and whatever you would want. its free and sweet. a bit confusing at first, but definitely powerful.

all the circuit diagrams can be found in the subversion repository. check out the pages in the wiki on each of the boards. i know a couple team members are doing it on breadboards so we'll see.

good luck, if you make some, please take pics and put them up for us to check out!

I suppose I rambled on a bit too much in making my point - which is this:

For someone like me, with very little electrical experience, the barrier to entry in printing, etching, drilling and soldering is very high. Compare this to buying a breadboard, parts and some connectors and plugging it in. I think it is much more accessible.

I do think making circuit boards as an important goal but I'd argue decreasing barriers to entry in a project like this is pretty important.

Does that make sense to you?

I am installing kicad as we speak and I'll try to have my breadboard images up in the next couple weeks. Thanks for the direction.

Yeah, it makes sense to me. For some reason, however, the bending of reprap to do integral circuitry and circuit boards has recently taken on an urgency among most of the development team which is a bit hard to fathom.

I doubt that a tiny fraction of reprap users will ever turn it to making a circuit board of any kind. There are too many other easy ways to acquire circuit boards and too few people who feel comfortable with electronics components.

i just remembered one of the main reasons we wanted to move to a pcb setup is that we will probably want to get some pcbs made professionally in the future. if we're already doing it that way, it should be pretty simple to transition.

Is anyone interested in going in on a group buy for pcbs? I wouldn't mind organizing one, although I'll probably be etching my own on Friday.

I'll try to get a cost estimate tonight.

Hmmm... I might be interested in going in on some manufactured PCBS... assuming the cost for the five boards would be $50 USD or less. Good idea you have. I always like the shininess of manufactured products. I will also be etching my own boards this weekend.

Zach,

Did I understand you correctly that you'd managed to get KiCad to generate PCB layouts?

Forrest

yeah... kicad does it really well. its just a bit confusing the first few times you try and use it. see the posts on the powercomms board on the main blog and wiki, all the files are generated via kicad.

yeah... i'd definitely be interested in pricing on that and/or getting in on it. one of the things i'd like to do is setup a shop and supply things like boards, components, and reprapped parts.

if we end up doing this group buy and can find the right price, i'd be willing to throw down a few hundred dollars and then provide boards to newbies for cost + shipping.

***if we end up doing this group buy and can find the right price, i'd be willing to throw down a few hundred dollars and then provide boards to newbies for cost + shipping.***

Be very careful. When you require a mandatory payment for something, even when you've deliberately set the price to only recover costs, most taxing authorities will treat what you've done as a sale and will require you to collect sales tax on the transaction.

Ignore that at your peril.

The way things are done in most places to get around that is to give away whatever it is that you want distributed and then ASK for a non-mandatory donation. That will generally keep the tax authorities away. Depending on the area of the country that you are in, however, you may want to look at either getting non-profit status or distributing what you have through Adrian and Bath University, who I understand have such a status.

I know it's fun doing things on an ad hoc basis, but you can get yourself in a world of hurt if you come to official notice. Leaving a paper trail of intent like you just did on this forum ain't the way to do it if you want to keep things informal. Indeed, after they passed the law last year that said that businesses have to keep logs of all IM and email traffic in perpetuity you'd better do such things over the telephone or by smoke signal at night.

Remember, we have Democrats running Congress and a President who's never vetoed a spending bill. They'll both be looking for revenue big time.

slightly paranoid, but true. however, there is a nice loophole. you only need to collect sales tax in a state where you have physical presence. that means if i ship it to a different state, it doesnt matter. when was the last time you paid tax on something over the internet?

we're not talking millions of dollars here, we're talking about getting boards made up to send out to contributors. if it gets to the point where it makes sense, then someone will start a non profit to handle distribution. i call that a 'good problem'. =)

The point I was trying to make is that Adrian already has a non-profit. No need to make one up. If you can get all that stuff in a padded envelope like you said you'll find airmail rates very attractive and with delivery in about a week.

I would probably also be interested in the fabricated circuit boards. Although, I'll probably still try to get those bread-boards I mentioned earlier set up. By the way, parts have arrived.

I also have a question about safety. I'm going to start another thread for it.

I thought I'd point out this article that went up on Scientific America yesterday:

[www.sciam.com]

Now, I don't think that the RepRap is quite at the point where it can be printing tiny superconductors on flexible displays... but I think it points to where printing your own circuits on something like the RepRap, however crude, could be a useful benefit to the project.

Forrest's objection to this idea was (partially) "...but how many people out there in the Third World are going to want to design circuit boards and how many are going to want to design three dimensional objects that they can actually use".

It's a fair argument to make, but I think he underestimates the value of having easily produced circuit boards. Aren't cheap electronics in the hands of third world peoples the whole driving force behind the OLPC initiative? Do you think that third world countries are lacking in electronics because they don't want/need them more than from economic concerns? If you could have a reliable store of circuit boards that could be shared, it would be easy for anyone with a RepRap to print boards for the RepRap itself or for simple radios or other devices. As the fella in the article says "

agreed. i was definitely a bit overzealous in my approach to printing circuit boards with reprap. however, i think forrest does underestimate the importance.

it is definitely 100% the priority of the project right now to get up and working a machine that prints objects in 3d with plastic well. that is the first step. that first step is huge, because once it is in the hands of developers around the globe, they can then use that to attempt to do all the things i've been dreaming about, such as automated circuit production.

the thing about circuits is that they are arguably the most complicated part about reprap. currently there are only 3 ways to get your circuits:

1. breadboard / stripboard / etc.

these are the current methods. they are more intended for prototyping and such. they can also be slightly expensive, and arent exactly idea for someone who is inexperienced

2. home printing & etch

these methods can be pretty hit or miss, require special chemicals, and are generally a pain in the but to get right. they are also quite intimidating for a beginner to try.

3. group pcb buy

this method is the most reliable, but also goes against the spirit of the process. with this, we are dependant upon an external supplier to manufacture something for us. granted, if thats what we have to do... then we have to do it. its also not very good for people who just want to design one board and make it.

plus i just think it would be cool to get reprap one step closer to an all in one manufacturing machine. i'm envisioning a day when you can go on the internet, download the plans for a robot, print off both the structure and circuitry with your reprap, solder in the components, slap on the motors and be ready to rock. this would be absolutely amazing and completely revolutionary.