I solder the body electric
When you design a printed circuit board, you often begin with creating a schematic that will be used as a reference later in the process. Of course, schematics for PCBs can be very long and complicated which can make checking them for errors quite difficult.
Here, we are going to tell you how you can effectively check your PCB schematic. Keep reading to find out more about this.
The volume knob in my wife’s Toyota Highlander behaved weirdly. As you turned it up or down, the volume setting would jump up or down, sometimes in the wrong direction and by an unpredictable amount. It didn’t give a linear output as you would expect.
What to do? Why, take it apart of course!
In my house, we have a ton of “batteried” devices. Having small children, in this modern age, one tends to collect a lot of toys, tools, crafts, and associated appliances that require an array of batteries. Triple- and double-As are in high demand, though 9V and even the C cells are occasionally used. Don’t even get me started with the coin cells.
I’m a notorious task-starter, and not a great task-finisher. My garage is littered with old projects that are collecting more dust than accolades. I can lean on the old, dependable excuses 1 but really that’s lame. If every moment is the new normal, then there aren’t any excuses. Our hobbies define us, and I love my hobbies. So it’s time to get serious about some side projects.
One thing that I’ve always responded to positively when it comes to my side projects is a good deadline. Nothing motivates like external pressure.
The deadline this time? Something called the Galactic Side Project Month (GaSiProMo) challenge. You’ve heard of Hackathons or Codefests? This is similar, but with a more sane schedule of an entire month for completion.
It was tempting to submit one of my more languishing, challenging old projects. But in the end I decided on something new and fresh, one that is slightly more achievable.
For GaSiProMo, I’m going to get this display up and running. It’s an intelligent LED matrix. I might even throw in a keypad to change the patterns and such.
I’ve had this display module lying in my Big Bin of Parts for… more than 10 years. At this point:
So there we go. I’ll post regular updates here and over at the GaSiProMo website. It’s time to blow the dust off some of these old projects.
Well, I’ve officially joined the DIY electronics community. Last week, I attended my first Maker Faire. It was my city’s first ever, and I was determined to take one of my projects as a booth participant. Nothing like a deadline to get my hind quarters into gear and (kind of) finish a project!
My office was liquidating a bunch of old computer equipment. In the heap, my eye was caught by a Dell box. “Hmm, what’s wrong with that computer?” And so began my next big obsession.
A while ago, I modified my daughter’s little kid kitchen. In that project, I found my design self teetering on that edge between two goals: get-it-done on the one side, do-it-right on the other. I had chosen the former and even my 2 year old (at the time) could see that this was a critical design mistake.
As a quick refresher, I had thought Those Thoughts 1. “Wouldn’t it be cool if her cute little IKEA oven had a light that turned on when the cute little door was opened?” Well, yes, but perhaps it would have also been cool if I’d considered the very likely fault condition wherein my toddler would leave the door open. Toddlers do that.
And you guessed what happens next: batteries died.
A very wise engineer once told me, “Rob, there’s never enough time to do it right the first time. But there’s plenty of time to fix it later.”
Well, here I am, fixing it finally.
I knew that a timer was in order. So I blew the dust of my Forrest M. Mims III Radio Shack booklets, particularly the indispensible 555 timer book.
When I was done, this is what I cooked up:
So to explain the “truth table“, the operation works like this:
One other critical circuit requirement that the above Mims diagram does not account for was with the trigger input. His classical circuit only triggers on level changes, active low. In other words, for as long as the input is held low, the timer would be in standby.
That wouldn’t work for me, since I wanted the timer to start when the door opened. That’s an edge-sensitive requirement. I found a nice, easy capacitive switch solution:
The results, finally, were as they should have been: nice well-lit oven that doesn’t wear out the toy batteries. My engineer buddy would agree.
My good friend James contacted me with an electronics problem. Seems his daughter’s cell phone was on the fritz. So I agreed to take a look.
She has a Pantech P7000 flip phone, but it stopped charging. I asked a few questions first to understand the nature of the problem. For instance:
James gave me some great info, so I knew what I was in for. My guess was that the charging connector on the phone was going bad. I’ve seen it before. James sent it to me to have a look:
The first thing I did was have a look at the charger, just to test out the verbal info I gathered from James. With a set of helping hands, I probed out the power and ground pins:
I saw a nice steady +5V, so the charger was good. Although its plastic shell was a bit wobbly, it seemed to be functional still. Now, onto tearing apart the phone.
I couldn’t find a tear-down guide online, so I had to figure it out for myself. There’s one obvious screw above the battery compartment:
But I had a hard time finding the other hidden screws. Turns out, there are four hiding underneath a bezel surrounding the keyboard:
Once those are gone, the assembly comes apart rather easily:
Now the back shell can be removed. When I did, the charging connector tumbled right out. So it was no longer even attached to the PCB:
Here is a closeup of the connector:
You can even make out the copper pads still attached to the pins, which have ripped off of the PCB. That’s never a good thing! This type of damage is actually quite common in consumer electronics. This interface isn’t always well designed on most cheaply produced gizmos. And yet, it’s an area that is very high-traffic; in other words, the mating cycles of the charger or serial cable to the phone is always quite high. As a designer, I would prefer these interfaces to be more robust. But then, I’m more interested in lifespan of my electronics, whereas most electronics companies would prefer you buy new products every 6 months. I digress.
At this point, I wasn’t yet sure I could repair this. There was significant damage to the PCB pads (some pads entirely gone!), so I first cleaned off the remaining pads by re-tinning 1:
Next, I cleaned off the pins of the connector. Then I re-placed the connector down on the board and soldered it back on. I got maybe 80% coverage of pins to pads. The number of pins on this connector is maybe 10-12; obviously only 2-4 of which are used for the power charger. So all that was strictly necessary were those sets of pins. As luck would have it, those power pins were still intact. The phone is back to life!
You remember the first phase of the iPod jukebox, yes? To jog your memory, the basic goal was simple. How do I make these dust-collecting components:
…work with my iPhone in order to have music in my workshop? Simple concept, not so simple electronics. The project is mostly a connectivity issue, i.e., there are tons of inputs and outputs that must all be managed with connectors and wiring and power regulation.
On paper, the system looks something like this:
In Phase 1, I had done a substantial amount of wasted work with one such cable: the audio/power cable for a first & second gen iPod. Since the project had been shelved so long, several generations of iPods and now iPhones have come and gone. Well, in that time, Apple has settled on USB as their power bus of choice, rather than FireWire. Thus, I had to likewise change directions on this project to accommodate my iPhone (rather than the antiquated iPods). Mounting options naturally have to change as well. And the overall enclosure gets modified too. It’s quite a ripple effect when your central component (the music player!) gets the switch-aroo.
I was locked in a brain-freeze for quite a while on this part, the mounting and enclosure. I had been stuck on the idea of trying to make a “pretty” Apple-esque Plexi box. But I finally admitted to myself that this is just above my skill set. I have a hard enough time making ugly black plastic kit boxes look pretty, let alone clear Plexi where blemishes show so easily.
So instead, I’ve decided to embrace ugly. Why not just make this phase of the project an intermediate step rather than the final step? My garage is already an acceptable and appropriately dirty place, as is the attached workshop. Just let this jukebox fit in with that kind of environment.
So I completely re-thought the enclosure phase. I began cobbling together other old cases, car mounts, and such to make a quick enclosure that would be practical, yet secure. Such parts included:
Mounts |  |  |
Cables |  | |
Chargers |  |  |
In putting all these items together, it now (unintentionally, I assure you) might resemble something else entirely, as you’ll see in the project gallery below 1. But hey, this jukebox does reside in the man-cave after all.
What’s in store for Phase 3? Coming soon, I’ll package all this mess a little nicer. I have some connections in the machine shop world. I also will reveal this gizmo’s name, so stay tuned.
A while back, a guy contacted me through my blog about contracting some monitor repair. He had come to acquire a bunch of LCD monitors that all had failed in similar fashion. So I took him up on his offer to repair them so he (and I) could resell them all.
Continue reading “Samsung LCD monitor repair”