Want to make an Arduino Mini-kinda Clone?

I was just curious.

The mini is "almost" the perfect for what I want do....

However,

  1. I don't need all the pin outs.
  2. There are no mounting holes.
  3. For the pin outs that I do need, I'd like to add a ground nearby as required.
    3a. The pins would ideally use some type of right angle friction lock connector.

So my question.

  1. How many of these boards would I need to make to get a similar cost per board to the ~19 bucks for the mini.

  2. Assuming that my surface mount soldering skills sucks. Is there someone that will print and solder the boards to my specs? At a hobby or production level.

Finally, I tried to play with Eagle, which appears to have a personal vindetta against me.

Is there another program that make the files required to send some place like batchpcb? Or that can work with eagle files?

Or is there a find a freelancer type spot for eagle gurus? What would I be looking at one a cost for someone to modify the existing mini-arduino eagle files to something that I can send off.

Ideally, I'd like to keep the cost of the mini-like clone to under 30 bucks.

The cheaper the better.

Thanks for any help. I'm very knew to the circuit scene. But I have alot of things I'd like to make.

Soldering SMD components is dead easy!

My personal exceptions are:

  • 402 sized resistors. Still possible, but not much fun. And if you drop them, you'll never find them again.
  • BGA/QFN as the pins are hidden under the package.

The TQFP package of the ATmega168/328 chip is really quite nice to solder. Even if you end up with many solder bridges, just use some solder wick and you're good. Just use lots of flux all the time. Ain't no magic. I recommend watching the soldering tutorials on http://curiousinventor.com

How many of these boards would I need to make to get a similar cost per board to the ~19 bucks for the mini.

Low volume PCBs from a quality vendor are probably in the $0.50 per in^2 range.

Assuming that my surface mount soldering skills sucks. Is there someone that will print and solder the boards to my specs? At a hobby or production level.

This will cost you a fortune. If you can not do the SMD assembly yourself you are much better off with TH. I do the SMD assembly myself. It is not difficult for
these types of components if you make a modest investment in tools.

Finally, I tried to play with Eagle, which appears to have a personal vindetta against me. Is there another program that make the files required to send some place like batchpcb? Or that can work with eagle files?

All PCB manufacturers accept Gerber files which is an industry standard. All EDA
tools that do not have a vendor tie-in will export Gerber files. I use gEDA/PCB
which is an open source EDA tools.

I am not sure how big a mini is. I am currently prototyping some smaller through-hole kits. It may be possible to use some of my existing circuit blocks to create a new
board. See wiblocks.com for some of the physical computing tools I have done.
Some other boards that I have done with the gEDA/PCB tools are at Loading...

(* jcl *)

I'm not opposed to attempting the soldering job.

I'll check out the tutorial.... I have fairly steady hands, but they eyes aren't what the use to be...

I just thought if this was a somewhat reasonable option, I got offload that job.

Any suggestions on the tools needed? Other than a big magnifying glass?

Or suggestions on a pcb supply house? Can the supply houses provide the pads presoldered? Or is that an extra cost that is not worth the effort?

Obviously, I've never ordered a pcb. And there appears to be a certain level of vocab that is required.

Thanks for the help.

Just finished watching the 101 Surface mount soldering.

They guy definately makes it look easy...

I think I might need more than the 10x eye lope though. But if the rubbing the braid across the pins when your finish works as well as he/she shows it.

Then maybe not.

It works.

Industry standard method :wink:

In fact even with the hot air tools, it is still easier IMO to resolder TQFPs back into place using the glob and suck method.

For all the PITA methods I watch other guys try to pull off, I'm usually quicker.

Desoldering can be stressful :wink:

By testing a freak idea I had after midnight (nothing good could come from that), I had to find out that 26V is no good for ATmega chips. It fried every single chip on my board... I thought I typed 2.6V on my power supply's keypad - apparently not. A good excuse to test the ChipQuik I ordered to replace an ATmega64 chip somewhere else. This stuff is just great. The paste flux has a totally weird smell and is possibly lethal, but the stuff works.

Anyhow, soldering TQFP chips shouldn't make you afraid at all. Removing dead ones requires the right method.

I recently assembled my first all-SMD board, and was surprised how easy the TQFP was to solder.

The 603 components gave me more trouble. The method I finally figured out was to apply flux, add a small blob of solder to one pad only, place the part with tweezers and then either press it down with my finger or grip it between the tweezers and the soldering tip while reflowing the blob, then solder the other side once it was aligned properly. For your first SMD job, I would recommend using an 805 package or larger for caps, resistors and leds.

I also wouldn't try it with a firestarter, get a temperature controlled iron if you don't have one. It seemed like a waste of money when I first started, but when I finally got one it made a HUGE difference.

As for loupes, the focal length is too short to use them while you're working (no force on Earth could get me to intentionally put the tip of a hot soldering iron that close to my eye), I just use it to check my work after the fact. If you need magnification while you work, I'd try one of those desk lamp magnifier things.

My tools and supplies list is at ---
http://www.luciani.org/getting-it-done/getting-it-done-index.html

If you design your own boards and use passive parts that are 0805 or larger
and lead pitches of 0.5mm or larger you should not have a problem. 0805's
are easy but 0603's are not difficult.

When doing your design use footprints designed for hand assembly.

(* jcl *)

If I use the exact same design/parts of the mini. It looks like there is 15 surface components.

I believe that I could solder the 328p fairly easily given a soldering iron with a small enough tip and if everything on the video works out in real life.

I couldn't use my current firestarter. grins

So I would need to get something else. Suggestions?

I can see the smaller components being a pain.

As for the diminsions of the board. My calipers say that it's roughy .7" x 1.3"

.48" or so would be as small as I could make it's width. Then I expect that it would be a little longer. 1.5'ish.

I would like to have it fit it onto .5" x 1.5" board. But it's a little bigger, it won't hurt. Primarily, it's the pin out locations and lack of mounting that hurts my current use. I could even kill off the mount holes, if I had the pins in the power location. I could make a little mounting box with slots for it to slide into.

Also, for design purposes...I don't know that I need the onboard reset switch, since I should be able to just cut the power. Or could make it 12 pins out... and use a remote switch.

Assuming that I leave all the components the same as the current mini. I see myself using the following pins: 4x Ground, 2x input, 2, output, 1x positive battery lead. 1x negative battery lead.

Then I would need the pins required to program it with the usb/serial.

So I'm thinking the Arduino mini with the two long row of pins remove.

Two mounting holes, 6 pins on one end for ICP, 12 on the other via a double row.

Thanks for any help.

I use a WES51, and would highly recommend it. It's probably about the least expensive temperature-controlled iron you can find, at least without going for some shoddy no-brand. I find that the slightly rounded tip that it comes with is best for packages like TQFP and SSOP, but I use the ETM tip for most other surface-mound parts. ETM is also great for use with a desoldering braid to remove solder from through-holes that are accidentally filled, which is I find really difficult with a larger tip.

.5" will probably be a problem unless you intend to put all of the power and I/O pins on one side of the board. My newest board is .5" wide, and you can see that there's not a lot of space beside the TQFP. Remember, you need space for traces to break-out the pins. If you want an FTDI header for programming, you need a row of 6 pins for that, although if you really want to save space, you can probably repurpose 2 of those as ground pins and 2 as I/O.

Another good iron is the Hakko 936

Both the above mentioned Weller and this one are industry standard units.

I'm biased, but I like the tips on the Hakko units better, but that's highly subjective as well. I've had my Hakko for over 10 years now, and have only ever needed tips.

Thanks for the iron links.

I'll check those out.

The board that you linked the picture to. Is more or less the size that I'm looking to do. Long and skinny, but I don't want any pins on the sides.

As above, I'm looking at 12 pins at one end(5ground, 5digital, 2 for 9v battery) and 6 pins at the other for the ICP. The more compact the better. I would like to seperate the 12 pins in to 6 pairs of pins.

Or this could be a ribbon cable that is cut to various lengths to reach the intended locations.

I really don't see myself reprogramming, but it would be nice to have the option. I just don't want to devote alot of board space to something that I will rarely use. Although, I know that if I have option. I'll be using it more than I plan.

I don't have a .5" width constraint. It could actually be bigger, but I like the idea of have as compact as feasible. I'd prefer it be roughly .5" wide and 1-1.75"'ish in length.

The largest that it could possibly be, would be about 1x2.5"

I've been looking around and soldering irons.

It would appear that I have alot more tip options with the Hakko 936.

However, I'm curious to know if there are any models that I want to stay away from. As there seems to be several different Hakko 936 sub types.

Thanks.

I'm going to trying my hand again at playing with the pcb design.

jluciani

I'm assuming that those numbers mean something to someone, but unfortunately. It is not me. I'm guessing they have something to do with the package size of the components.

I was curious if the program that you suggested was able to make use of eagle part files. I haven't downloaded it yet, but plan to in a few minutes.

Thanks all,

You're going to have post a link to some of these 936 variants.

If you go with that one, get the one that matches this one:
http://www.hvwtech.com/products_view.asp?ProductID=209

...
It would appear that I have alot more tip options with the Hakko 936.
...

I don't know what crazy tip types you plan on needing, but I bought half a dozen tips for mine, and all but two of them still have the factory tinning. Any soldering iron will come with a tip that is ideal soldering PTH components and adequate for 99% of the soldering work you may need to do. A sharper tip will be helpful for some surface-mound components, but what else are you going to need?

Remember, the tip and the shaft that it connects to get very hot when you are soldering, and it takes a while to cool down, so you don't want to be changing tips all the time. It's best if you can complete a job with only one, and for most jobs, the one that comes with the iron is the best choice.

Buy whichever one you want, but unless there's a specific style of tip that is only available for one iron that you think you'll need, don't let tip selection be the deciding factor.

lol

I don't expect to be changing the tips very often or ever. At least not when they are hot. You only need to grab a hot iron once to learn that lesson.

As for the current use I see for the soldering iron.

SMD components. As talked about above.

Sub-cell battery packs.

Misc other sodlering tasks solutions.

i.e. wire to connectors etc.

I just thought it was neat, that if the task required. There were additional tips around.

Also, the Hakko appears to be a tad bit cheaper. The one that I'm currently looking at is new and ~70 bucks shipped with 10 tips of my choice. Which was roughly 30-50 bucks cheaper than the Wellers that I could find.

If there is a huge difference between the two, then I'll opt for the better. However, for the amount of soldering that I will do. I'm mainly looking for the iron that has the proper tip and steady voltage to do the job.

back on topic

I think I finally started to beat eagle into submission. I have a PCB that is laid out roughly the way I want it. In a fairly compact size(7"x1.4"). I used the reference schematic from the website.

Although, I'm confused. Since on the of the connectors is name something, but plugs into something else. I don't know if this is by design of a misprint.

i.e.
On the FTDI Basic connector.

TXO connected to RXI
RXI connected to TXO

I left it as it was, but seems a little strange.

That's correct. TX is transmit and RX is receive, so the atmega's TX line has to connect to the FTDI's RX, and vice versa. It can be confusing, you just have to remember which device's TX/RX you are working with.

Looks like I'm going to have to bring out the programming pins also, to burn the bootloader.

I thought I could buy the chip preloaded, but I guess not.

I'm thinking about using just pads, and a little pogopin programming station. Since the goal is to make this thing small.

On the schematic, it has the SCK pin pulled to ground through a resistor. Is this required?

If I'm reading the info page right. I need the following pics for the in circuit programming.

GND, RESET,+5V, SCK, MISO, MOSI

Am I missing anything else?

I brought out the 6 pins for the FTDI programmer board, then I bought out the pins I want. Now I need to program it with the

No, you shouldn't need a pulldown on SCK. I think the resistor you're looking at is a current-limiting resistor for the pin 13 LED.

If you design your board so that it uses digital pins 11-13 for I/O, they will already be exposed. If you also break out the reset pin, you can wire up a custom cable to temporarily connect to the pins you're already using. Then you don't need a separate ICSP connector.

You could also pre-bootload the chips yourself. I recently saw a thread that mentioned doing this by holding chip down on a footprint connected to the programmer without soldering it in place.