Guess what's coming in the mail to me? (Done! Video page 5!)

[MarioOwnsAll]

what did you use for a screen?

[dragonhead]

what did you use for a screen?

holy **** wow. you did not just ask that....

Reading Skilz 101

i know its a minor tweak, but what about something more like this?

[Life of Brian]

Or you could use the cheap li-po's I linked to around a month ago.
Just kidding. It all looks great.


(I still think that the AA's are the main hindrance of this portable.)

I plan on offering two options - AA's for one price and with the cart sticking up a bit, or lipo's for a bit more and with the cart flush. I'll let the buyer decide if it's worth the extra cost.

i know its a minor tweak, but what about something more like this?

Does it bother you that the volume adjust buttons are split by the select and start buttons?

Reading Skilz 101

Quoting yourself now, eh?

[64M320N3]

I plan on offering two options - AA's for one price and with the cart sticking up a bit, or lipo's for a bit more and with the cart flush. I'll let the buyer decide if it's worth the extra cost.

Sounds decent enough. Are they going to be rechargeables or is the buyer going to go out and get some? Regular AA's are horrible.

[Life of Brian]

Well, either way the buyer would provide them. I'm going to offer the option to reduce the cost up front for the potential buyer. And since I'm using a TI regulator for this system with a pretty energy efficient screen, alkaline AAs actually last a long while. Haven't done any testing yet, but I've been using the same set of AA batteries the whole time I've been building the prototype.

[nevermind1534]

The lithium AAs are really good for electronics. They keep a constant voltage until they die. Might not matter as much, though, since it goes through a regulator.

[64M320N3]

No, that definitely matters because regulators have dropout voltages.

[Life of Brian]

Well, I might as well combine my thread from the Technical Q&A section about digital pots and this thread because the two are quickly merging as I continue to build this prototype. Good news - a potential buyer contacted me about purchasing this unit, so I'm highly motivated to get cracking and finish this sucker up!

To catch everyone up to speed, I am building an audio amp because the AEI Comp screen I'm using does not come with one. After reading about Ben's C64 laptop that used a digital potentiometer to adjust the volume, I decided I just had to try it. Using a digital pot allows me to use two buttons to adjust the volume instead of a clunky dial or slider. Since my goal with the design of this portable is to (eventually) make it as commercial in appearance as possible, using a digital pot was a natural choice.

This is essentially what I built today using a TDA7053A stereo amp and a DS1669 digital pot. The digital pot is basically a drop-in replacement for your standard potentiometer. The pinout to the right is a close-up of the area circled in red to the left.


And here's what it actually looks like when haphazardly pieced together on some breadboard because Brian was lazy and didn't want to fire up the soldering iron




If you take a moment to look at the schematics, it's really a pretty simple design. And what's more important, is that it actually works! Hooray! Except for one major drawback - it sounds like crap! Oh no! I've been tweaking values here and there and I'm slowly getting a better sound, but it still sounds like a homemade audio amp playing through cheap speakers... which it is. If I turn the volume up too much, the audio gets awfully "fuzzy" and the volume level then drops very quickly, as though the amp is being overloaded or something. Aside from fiddling with resistor or capacitor levels, is there any way to cap the volume and clean up the audio? Any help would be appreciated.

Here are a couple of relevant links:
TDA7053A data sheet
DS1669 data sheet

The particular pinout I was using for the TDA7053A was from kitsrus.com for a 1W stereo amplifier with DC control - something that Rekarp tipped me off to a long while back.

It's so hard to take a good picture of this portable in this room - I need to get some better lighting. The screen really does look great in person.


I figured out a way to mount the cartridge slot that seems to work pretty well - drill a couple of holes and use a couple of threaded spacers and screws to attach it directly to the case.




The dpad and ABXY buttons are lined up to use identical boards for their underlying rubber tact switches - convenient!


Slowly but surely I'm getting there. Sloooowly slowwwly slowly...


Again, I'd appreciate any pointers on the audio amp. I might try building one using an LM386 and this digital pot and see how that works out. As of right now, it just sounds crappy and I don't like it! All I want is a perfect portable - is that so much to ask?

[dragonhead]

lookin good man

[sbains1989]

looking awsome! keep up the good work!

[dragonhead]

looking awsome! keep up the good work!

your avatar is HUGE

[Triton]

With my LM386 audio amp circuit i had to play around with values a LOT to get halfway decent sound out of it, its a little tricky to get the gain set right on these things. i know its not 100% applicable in this case but here is the schematic with the values i used

an here is a slightly more complicated schematic i drew for project_failure, i was stupid and forgot to write which IC was used tho >.< it was a stereo amp similar to yours i think.

[Life of Brian]

Yay! I got it working! Ha - turns out the location of resistors R1 and R2 matters. According to the diagram, they're supposed to go before C3 and C4, not after. Oops. The audio amp works perfectly now.

And what's more, I've got a video to prove it! Hooray! Here's the YouTube video, in all of its unedited glory.

That was the last major hurdle in getting this thing up and running. Time to get cracking and race towards the finish!

[Life of Brian]

So, I gots me an idea. When I get around to ordering a new case and I'm all set to build revision number two, I think I'll record video with my camera each time I'm working on the portable. Since I have just about every part of the design figured out by now, the building process should go pretty quickly. And since I'll be recording each time I work on the thing, I can discuss parts of building a portable that I usually forget to mention during my typical "completed project" videos. Hopefully I can share some more tidbits of wisdom about what it takes to build a portable and the uneducated masses can see firsthand just what it takes to make something of this complexity. Naturally I'll edit it down so the most interesting/relevant stuff will be included instead of hours of me quietly soldering. What do you guys think?

[poopiesman]

Sounds Brilliant! Portable-making can NEVER have too much documentation*!