Step 3: transfer to copper

These are the generic instructions that I follow anytime I etch my own PCB's:

You need an Iron, a Scotch-brite pad, a few paper towels, and some Acetone.

Before you start, plug in your iron and turn on to highest setting.

1. scrub copper clad with a scotch-brite pad until shiny
2. use acetone on a paper towel to wipe off copper dust from copper clad
3. repeat step 2 until there is NO visible dust being removed, folding the paper towel after each wipe. re-apply acetone as needed. If you don't get ALL the dust off, it will not transfer.
4. Let dry for a few minutes.
5. pre-heat the copper clad with the iron for a minute or so, using a freshly removed piece of magazine paper (the less pictures the better) between the iron and copper clad.
6. remove iron, and CAREFULLY place print onto the copper and press it down.
7. add another piece of magazine paper between your print and the iron to keep from ripping the print.
8. Press hard with iron, moving every 30 seconds for about 3 minutes.
9. remove iron and let cool for 10 minutes.
10. place in container with warm soapy water for 20 minutes to dissolve paper.
11. remove paper with thumb, scrubbing it until it is all gone and there is only toner left.

12. If you have any smeared tracks, clean them up with a small flat-head screwdriver. If you scrape too much away, use fingernail polish to add some more "toner" where needed.

on to etching...
 Now I would assume that since I have a 328, that I should have another 328 to match right?
not necessary, they are independent of each other, so if the code on 1 of the chips needs to be much larger, you can use the 328 for that one. I have mixed them with no problems.<br />
So I could use an Atmega8 as the 2nd core, with it's own 8mHz crystal, and do the timming adjustments through software on any of the cores... correct?
Really interesting... the Atmega8 is SO cheap that makes a great candidate for an auxiliar I/O board (with fancier possibilities)!<br>Maybe a couple of them on the same shield..<br><br>Thanks a lot for the instructables!!
Wait, I'm a little confused.... How do you program the second atmega? Does it just get its own binary? How do you hook it up to program it? Looks cool, I'm just not sure how it works.
you can upload the same test code to both Arduino's to see that they work properly, then make up your own code to go on the 2nd Arduino. If you don't yet need a 2nd Arduino (or more commonly, an Arduino Mega) then this instructable is not yet for you. Once you get to the point that you need either more than 6 analog inputs, or more than 20 digital I/O pins, or more than 2 external interrupts, or more than 6 PWM outputs pins..... you will quickly see why this board can be very useful for how cheap it is to make. I used this board to decode a failsafe signal from my R/C receiver to keep it separate from the main processing code, for added safety. If the main processor fails, I can still disable the 200lb bot. You can use it to power 40 LED's, or if you need 12 PWM outputs, or 12 analog inputs, etc....
Ah. So, two programs for the two arduinos. Don't worry, I see the merits of the project, especially for big bots like yours. I would hate to have that running around my neighborhood.
Great idea, johndavid400. I'm just curious why you didn't piggyback off of the Arduino's 5v supply and oscillator. I can understand not sharing the oscillator if that would require soldering directly to the Arduino, but I can't see what the issue would be with sharing the power supply.
It does share the power supply.&nbsp; You can use the jumpers to select 1 of 3 power sources. You can tie the core2duino directly to the base Arduino +5v (regulated), or you can connect the VIN (voltage&nbsp;In) pins together and let them both use their onboard 5v regulators to supply power, or if you have neither a&nbsp; USB cable or a DC&nbsp;jack, you can use the screw-terminal on the core2duino to supply power to both itself and the base Arduino. So either one can power the other or just itself. The jumpers allow you to choose which source you want very easily.<br />
Cool I guess I should look more closely next time :)<br /> I haven't done any Arduino stuff (yet), but do you know if it would be possible to share oscillators if you were building your own Arduino clone unit?
not sure if you can share the oscillator, seems like it would be possible if you made the base Arduino as well, and 2 header pins that are connected to the Xtal1 and Xtal2 pins of the Atmega168... but they are not accessible on the standard Arduino as far as I know. The oscillator only cost $0.54 each and you only need 1 per Atmega that you use. You can use the Atmega with it's internal oscillator, but it will only run at 8mHz (instead of 16mHz), so every function based on timing will be off, like delay() and millis(). <br />
Also, interference along the oscillator lines can cause crazy bugs.&nbsp; That's why most designs have the oscillator as close as physically possible to the chip<br />
Nice project!<br /> <br /> 1) Is a *kit* coming soon?? &nbsp;;)<br /> <br /> 2) Does this extend the current set of pins within my *main* program or are we really programming 2 different chips at this point?<br /> <br /> I am trying to get more external interrupts (without having to buy a Mega)<br /> <br /> Maybe some examples on using the different pins (which are for chip1 and chip2)???<br /> <br /> Thanks and again, nice job!<br /> <br />
In revision 4, the one without the extras, what is the value for the capacitor? And I assume that the resistor is for the LED and not a diode or something.
the capacitor is probably not even needed, unless you are going to be flashing a bunch of LED's or something that might draw excess current from the base Arduino. I&nbsp;put it there to give the core2duino some extra juice if needed... so I&nbsp;would use a short (in height) electrolytic capacitor, whatever value you have between 50uf and 250uf (10v or higher). You want the capacitor to be about the height of the female headers, so you can add a shield on top later if you like. Also, I would use either a 1/8w or 1/4w, 330ohm resistor and a 3.5mm LED for the power light. <br /> <br /> hope this helps,<br /> ~jd<br />
also, not sure if said much about the Eagle file, but:<br /> <br /> The red lines are jumper wires. There should be a 10k resistor underneath the 28pin dip-socket for the Atmega168 (it is the pull-up resistor for the reset button).<br /> The reset button goes above the atmega&nbsp;(I put 2 sets of holes for different size buttons). The 16mhz crystal oscillator goes to the left of the atmega, orientation does not matter. The 2 holes to the right of the LED&nbsp;resistor should be populated with (2) .1&quot; male shrouded breakaway headers (these are the VIN selector jumper pins and are only needed if planning on using the power input from the Core2duino). The outer-most set of Arduino pins on each side should have the stackable headers. The inner-most set of pins use the regular female headers.<br /> <br /> Again, you will want to solder the stackable headers first! you will be able to more easily access them with the soldering iron.<br />
<br />
&nbsp;cool, what's it do
&nbsp;How would you do this on a protoboard/perfboard? I have absolutely no experience with etching and thus would like to use a protoboard/perfboard instead.
&nbsp;I've always etched my own boards, but since I don't have access to a laserjet printer to make my own resists I have to use a paintpen or a sharpie. One thing I also use is a perfboard. I use it to layout my grid and do proper spacing. So I'd say you're better off with a perfboard if you don't already have a etching setup. And no offense to johndavid400, but I'd say the perf will look a lot cleaner and more organized.
you can do it, but you will have to use bent <a href="http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1206626508/30" rel="nofollow">stackable-headers</a> like these (because the Arduino header spacing is .15&quot; instead of .1&quot;) and the <a href="http://www.radioshack.com/product/index.jsp?productId=2103800" rel="nofollow">perf-board</a> will require a lot of wire. Other than the <a href="http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&amp;name=X908-ND" rel="nofollow">16mHz resonator</a> (center pin grounded, left and right pins to&nbsp; Xtal1 and Xtal2 on atmega), the <a href="http://dailyduino.com/wp-content/uploads/2008/11/arduino_pinout.png" rel="nofollow">Atmega168 pinout</a>, and any <a href="http://www.radioshack.com/product/index.jsp?productId=2062599" rel="nofollow">5v regulator</a>, you just need a bit of patience and some good wire strippers. You should also take some pics and post an instructable showing how you made yours. I have made several Arduino dummy breakout boards on perf-board, but they all had screw-terminals instead of headers (they are not stackable).<br />

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Bio: I have always been one to take things apart to figure out how they work, so most of what I own has been dismantled. If ... More »
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