Arduino Mega Shield Template in Eagle – Improved!

Exactly one year ago I made a blank shield template for my Arduino designs. I’ve had the opportunity to use it several times. It was OK, a serviceable starting point for Arduino-based projects. I’ve just recently made improvements that will help speed up the design process:

• Signal names match names in the Arduino silk screen

• Top layer has a copper pour for the +5v circuit

• Added a frame to the schematic

• Arranged all Arduino connections on the right-hand side of the schematic page.

These are small changes, but they make a big difference in your ability to organize and check your design effort.

For instance, I like my circuits to “read” from left to right. For me this is less confusing than other formatting choices. As for signal names, other shields cobbled from the Arduino reference design often preserve the Atmel signal names, rather than the signal names from the Arduino Hardware Description web pages. I hope these files work for you.

Get the files here:

http://www.mediafire.com/?1z98ws4wyh232d6

Why nothing gets done around here

“My computer won’t read my CDs”, said my darling wife. Her computer is a relic, but I was hoping that it would last until 2012. She wanted to put songs from Xmas CDs onto her iPod.

I’ve only ripped a CD on rare occasion, and I dislike iTunes, so I was not familiar with this. I reviewed the steps involved. Her process seemed hunky dory. I next wanted to look inside the computer case. As I’ve done many times before, in countless circumstances over he last three decades, I  took off the computer’s cover to see what’s up. This has always been a harmless procedure. Not today.

This computer is in a dark cubby hole underneath the office desk. I crawled under the desk and removed the side cover. As I brushed my hand against a ribbon cable, a spark,  for the briefest instant, illuminated the inside of the computer case. Then all was dark and silent. SOMETHING was wrong. Time was running out.

Luckily, I had a spare power supply. I swapped the power supply. Nothing. I was about to panic. Instead, the wisdom of age prevailed. I ripped the CD to iTunes on my PC and then downloaded the music via CopyTrans to her iPod nano. With that crisis averted, I had one crisis left: the wife’s dead PC.

Let me tell you about our computer set up. We have two nearly identical PCs. I built them up in 2003 or so for gaming. Back in their day they were fast machines. Time and technology marches on – these machines are showing their age. For example a few months ago I put a new HDD into her computer. I discovered that IDE HDDs are becoming a rarity. I got her a 500GB SATA drive. Needed an adaptor to make it work.

For our nearly identical PCs, the sameness applies to the Mother Board, the CPU, the case, the memory and the video card. So they’re really a little bit different. One difference that I don’t quite understand is that on my PC, switching the rear power switch ON is all that’s needed to start the PC. On hers, one must switch the rear switch AND then press the front reset switch. So in my haste I feared that her power supply failed. Not so.

I went out for the day. By the time I got back to troubleshooting her computer, I was confident that the power supply was ok. I next checked her HDD. I put the drive into my computer. While installing the drive, the drive’s IDE to SATA adaptor crumbled in my hand.  As I said these are old machines. When I recently rescued  her computer from a drive failure, the only viable choices were SATA drives. 

When I installed this set up, the adaptor worked great, although its mechanical construction was flimsy. The SATA connector on this device is a through-hole connector repurposed as an edge connector.  In the photo above you’ll see that the connector is no longer attached to the motherboard.

As verified each component of the computer, one by one. The only failure, it turned out, was the SATA to IDE adaptor. That was good news, however, soldering those 20-plus contacts would be impossible, and my dear wife was anxious to use her computer. What to do?

At some point I noticed that the big section of the connector was for SATA power. Power is easy to come by, so this part of the connector seemed unnecessary. The smaller section of the connector is SATA data. I Googled SATA data and took a quick primer on all things SATA. SATA data is a pretty clean high speed bus. It is composed of 7 signal connections. The seven wires are: two differential  pairs (in and out) and three ground connections. However, soldering the original connector back into place was just too difficult.

I surmised that the transceiver on the adaptor could carry the signal past the original connection point by a few more inches without problem. I would solder cable end in place of the original connector. I ran to radio Shack and bought a SATA data cable. Once I was back home, I cut the cable in half and prepared the wires.

It’s a flat cable so it was a breeze to verify the proper pin out. The cable jacket was elegant. Each twisted pair was in its own section wrapped in foil with two ground wires.

 

I connected everything 1 to 1, save for pin 4, where I connected two ground wires, one each from the two twisted pair bundles. With a little bit of electrical tape to protect from shorting, I was ready to roll.

I plugged the IDE cable into the adaptor, as well as a power cable. On the drive, I plugged in a SATA power cable  from the power supply harness and the SATA data cable end that I had soldered onto the adaptor board. I powered up the computer. It booted up and has run fine ever since.

I now know a lot more about SATA and once again, I performed some intense hardware surgery and the patient survived!

Blank Shield Schematic for Arduino Uno

 

For a recent project, I created a shield template for the Arduino Uno. MOST of the bugs are out, as I did use it once and then corrected the few shortcomings that I encountered. These linked files should give you a decent head start over creating your own shield in Eagle CAD or adapting an existing design for your needs.

What I did: Starting with the UNO reference schematic, I removed the parts that I did not need and left the parts necessary to interface to the Uno.

I made a shield template that puts the user at this starting point:

• All schematic parts are on the 0.1 default grid. (Until you try to

Technorati Tags: Arduino,sheild,template

• work with with parts off of the grid, you’ll not appreciate how frustrating this can be.
  
• I put all important top side text on to layer 21 so that my preprocessor put the text onto the Gerber file silk layer.
  
• I put all of the Arduino interface connectors on the far right side of the schematic because I like my circuit to flow left to right.
  
• I framed the schematic.
  
• On a hunch, I left a few filter caps and LEDs on the board.
  
• Also I have a section of called Commonly Used Parts. <Common Sense alert> If you don’t use ‘em, delete ‘em.

Get the schematic and layout in a zip file here:
http://www.mediafire.com/?0kt85e6i0tc7ol0

Hard Disk Repair – Not for the Faint of Heart

Recently I updated our two computers with new cases. Not a big deal, as far as upgrades go. It started when my power supply fried. It was cheaper to buy two brand-new cases with power supplies from Newegg than it was buy one power supply from Best Buy.

When swapping the components in my wife’s computer, I noticed that one of the HDD was hot to the touch. Now anyone familiar with the inside of a computer case knows that warm is OK and hot is cause for concern. Like most people in a hurry, I went about my business and ignored this leading indicator of a problem. Two days later I got a call “ITunes can’t find my music files.” The problem, and its diagnosis, flashed before my eyes instantly. Later that day I confirmed my suspicion. The drive was now stone cold dead. Luckily this was the secondary drive (D:) and all it held was mp3 files.

I started to Google “drive recovery”. Somehow I got on to drive repair web sites. Forty bucks would get me a used, tested replacement circuit board for my Maxtor 80GB hard drive. The majority of these sites were from Asian companies with broken English explanations of the repair process. It seemed daunting, because a few steps alluded to implicit contingencies on how to repair my HDD.

Most troubling was this instruction:

In most cases, you should exchange the BIOS chip before you swap hard drive PCB;

Holey molé! How do I determine if this applies to me? And worse still, I didn’t have the friendly little eight-pin SMT BIOS IC like many drives have. Do I need to swap out the 168 pin QFP? Not with my equipment.

Soon, through EBay, I found the web page for PCB Solution. I use their web site to find my matching PCBA and sent them an email. Although it was now midnight I got an immediate reply from Kevin:

This board is direct swap. Some board required more work, but not this one. If you prefer, you can tell me the current symptoms of your hard drive, and I can give you an estimate on your odds of success. There are no refunds with this purchase. I hope this helped and please let me know if you have any other questions. 

So in my return email, I explained my plight. Kevin’s response contained the helpful response that I needed:

If the drive doesn't spin up, and wasn't dropped, I think the chances of
success are quite good.

Bingo! I could proceed with confidence. I ordered the PCBA through eBay and waited. When it arrived, I opened the package and the contents impressed me.

I expected to see the PCBA wrapped in a metalized poly bag. It also came with clearly written instructions and a Torx screwdriver. Great!

 

1 – Remove the PCBA

In the picture, notice: (1) Torx drive, (2) PCBA covered with rubber membrane, HDD, (4) loose Torx screws, (5) replacement instructions and (6) spring pin contacts to interface the PCBA to the HDD chassis. At this point I was still wondering if I had squandered $40.

 

2 –Installation

Simply put the membrane on the replacement PCBA and screw it in.  The spring pin contacts on the HDD chassis help to make replacement a breeze.

3 – Configure

Simply put the jumper on the new board so it is configured like the old board. If you lose track, simply follow the graphic on the front of the drive.

4 – Test

I installed the drive in my computer, and booted up. Success!

Drive D: is fully recovered and operational.

Effect Number Two: Muff Fuzz Complete

We’ll, the Muff Fuzz is complete. It looks good too. While it obviously is an amateur effort, it came out a lot better than I expected. It is named after a friend who helped me quite a few times through this project. In retrospect, RAW Squid is a bad-ass name for the fuzz box.

In my last post, I commented that I was having trouble getting everything to fit. In the end, I was able to fit everything inside this little old Hammond 1590B enclosure, but it is tight inside. I was able to keep the PCBA connectors, so everything is readily interchangeable. If I continue to build guitar effect pedals I’ll design for a slightly bigger enclosure.

The original Muff Fuzz had a volume pot, but no tone control. I elected to go without a volume pot. That may be a mistake, as the output from this pedal is louder than straight through bypass. If required, we can add one later. I built this effect with true bypass. I don’t know how the original Muff Fuzz bypass was set up.

On the circuit board, you’ll notice the white connector. The connector hosts a plug in module for the clipping diodes. You can see the clipping diodes in the schematic diagram below. I installed the clipping diodes in a plug in module so that the pedal is easy to experiment with.

The most basic mode (1) is no diodes. Without clipping diodes the circuit is essentially a Fuzz Face with alternate component values. Configured this way, the sound is similar to, but has more buzz than a Fuzz Face. Adding the back-to-back clipping diodes, (2) the circuit is as shown above. Lastly (3) I made a  a three diode version where one of the legs has with two diodes in series. A lot of folks call that the tube screamer mod because the diode clipping is asymmetrical.

We could make even more versions, if we were to toss germanium diodes and filter capacitors into the mix.  Also, I suspect that tone control could be added in place of the 2.7k ohm resistor.

I’m eager to have this effect pedal evaluated by an objective and seasoned guitar player.

 

Effect Number Two: Designing in Three Dimensions

For my 2nd effect, I planned to build a Muff Fuzz. It looks like I’ll have to take a step back on this one. This is destined for a friend, how has served as my music industry consultant. My idea was to have the circuit connectorized so that we could easily swap the circuit. Also, I wanted to put it into a sleeker case than my first Fuzz effect. I now know that the beautiful Hammond 1590B enclosure can accommodate the circuitry, but not the connectorization scheme.

It looks like I’ll have to hardwire the components. Luckily, this does not preclude all experimentation. The Muff Fuzz is essentially a Fuzz Face front end, with clipping diodes on the output, like an MXR Distortion+.  There are many ways to select and configure the output diodes. Soon, we may know which are the most interesting combinations.

Parting Thoughts on the DOD FX55

After I fixed the effect, I put it back together, finger-tight. That is, installed all of the hardware and screwed the hex nuts on finger tight. So everything was assembled, but loosely.

I inserted the FX55 in the signal path, between my guitar and amp. Instant success. But, wait I couldn’t turn it off! Actually every time I stepped on the switch, I heard a click coming out of the amp, but the  effect remained ON. Well this effect uses active switching, rather than true bypass. The schematic indicated that the case played no active role in the circuitry. The problem was one of these two choices (1) circuit noise or (2) I broke something. After tightening all of the hex nuts and screwing the case on securely everything worked fine. Note to self: this item is noise sensitive.

Get your own 5 in 1 effects PCB

If my guitar effects projects interests you and you’d like to build your own guitar effect, then you can get your own circuit board at Batch PCB. You can choose one of the circuits listed in the Burnout Sound schematics page, or a few others as well. For example I am presently building a Muff Fuzz circuit on the 5 in 1 PCB.

The PCB has both a ground and a VCC plane . There are provisions for both battery and line power and a circuit board is so much cleaner and rugged as compared to perf board construction methods. It available from Batch PCB. With shipping and handling, it’s more expensive that I’d like, but I do not set the prices.

 

DOD FX55 Guitar Distortion Effect Repair

A good friend let me borrow a few of his commercial  fuzz effects so that I could use them to compare to my FuzzFace clone and evaluate my handiwork. One of those items was the DOD FX55. I’m not sure how to describe the sound from the FX55, but when I play with it, I wish I knew some Deep Purple tunes.

Anyhow, the output jack on the FZ55 was finicky and I offered to fix it. At this stage of my interest in guitar effects, I’m glad to get inside as many effects as I can and see how others have designed the mechanical aspects of their effects.

DOD FX55 Distortion

This venerable old beast has given years of service and now it needed some service. Its problem was that the output jack has to be in an exact certain position, or it would not work. Luckily, I had a plastic replacement jack that fit into the DOD.

Have a look inside

This effect was made in the USA, back in 1983. Not very pretty. That’s the defective output jack with the sky blue and black wires attached. Once the jack was unscrewed from the case, its problem was obvious. The tip contact was bent. Take a look.

Old (Red Arrow) and New (Green Arrow) Output Jacks

The red arrow points to the broken jack. Notice the twisted tip contact, as compared to the good jack (green arrow).

This effect was actually easy to service.  The PCBA is held in place by the potentiometers. The wires are long enough to move things around without stressing the wires or the components.

 See how the PCBA flips out for easy access.

While I was inside, I also replaced the battery connector. There’s not much to it. Used FX55s are cheap on eBay and there are a few web sites that detail circuit mods. The fix required abut $4 in parts and a few hours of my time, but I got a hands-on peek into another stomp box.

Fuzz Face

For my first project with the Five-In-One PCB, I built up a board as a Fuzz Face clone. Thing went smoothly during assembly. With one capacitor tweak, it worked pretty well. I added a stomp switch so that the effect is practical. The Original Fuzz Face had a volume pot and a tone control. The volume pot seems superfluous, as the effect output is a few dB lower than in the bypass position. I am curious about the tone control, so I will add that soon.

That’s a three pole, double throw switch to give true bypass and an Effect-On indicator LED. Since this a prototype, I put aside my Hammondenclosure for the time being. I followed Andrew Carrell’s lead and mounted the PCBA in a 4 x 4” electrician’s box. The electrical box is cheap, roomy, and readily available, so it’s a reasonable choice for anyone.

I’m someone who is relatively inexperienced with guitar effects. So at first, when I had the effect working, I really didn’t now I it worked correctly. Luckily I have friends. On Wednesday a package arrived with several guitar effects, on loan from my buddy Al. My first choice from this grab bag of effects was the Tweak Fuzz. This is a Seymore Duncan product that allows you to adjust the tone to match several popular styles of Fuzz. To my inexperienced ears, my FuzzFace compares favorably with the Tweak Fuzz.

The fuzz works identically with either box. With the guitar volume pot at full volume, the fuzz tone really cranks in. As you back off on the volume pot, the tone cleans up. I’ll have to work on embedding sound clips into the next post, so that you, dear reader, can listen and compare.