Author Topic: a slice of pi (pics yo)  (Read 995 times)

0 Members and 1 Guest are viewing this topic.

Online Nuke

  • Ka-Boom!
  • 212
  • Posts: 6,718
  • Mutants Worship Me
a slice of pi (pics yo)
ok so i decided to show off my stuffs. a couple days ago i got my raspberry pi. i then ****ed around with linux till i was sick of it. so instead i put my time and energy ito a couple other things. first of which every computer needs a case. since the pi ships caseless you usually need to provide for this yourself. one thing i have in abundence is legos. technics all, with some mindstorms thrown in for good measure. so it seemed like a choice building material for the case.

another problem i had was the lack of an appropriate power supply. somehow i was under the impression that i had a microusb adapter somewhere. turns out i did not. i had a bunch of usb adapters but these were for the larger though slightly similar mini b (i think) configuration. why they didnt just throw on a standard 5v barrel jack instead is beyond me. theyre cheaper. but i found out that you can use pins 2 and 6 on the gpio header. this bipasses a protection fuse, but oh well. safety 3*10^666rd. so i have a box full of linear regulators. some of them can do 100mw, some can do 500, but i used a big ol' to-220 package lm7805 which can feed an amp and a half with only some minor heating issues.

i had a supply running on a breadboard for the first couple days, which ultimately proved to be unreliable due to cats. well the next obvious step in prototyping is to break out some strip board and cobble a more semi-permanent solution. of course i skipped that step right into actual board design. its a fairly basic circuit after all. i didnt want another wall of text post like i posted so heres some pics instead:

starting off a horrible pic for demonic effect. gradient rendering and 666 in binary etched into the desk next to it. idk why i kept this one other than that it looks like it came out of hell, but here you go.



why i picked yellow was beyond me, i could have built it in red. black was not an option because i dont have any of those cool panels in black. the composite and audio ports have good access, the ethernet jack is a little bit recessed but is still accessible. the usb ports are almost flush with the exterior but its easy to plug in most normal sized usb plugs.


this pic shows the card slot, and impossible to find unless your a phone whore micro usb plug that i will probibly never use. hdmi plug could be broken out better. thing is i dont have a single hdmi cable at all, so i couldnt test it to see if it connects up fine. you can see the edge of my power board here. it has a power switch a 12v barrel jack. the 2 pins next to it are for connecting a battery pack. the two pins on the other side of the switch are power output. i was going to connect a cable from here to the pi, but decided to connect it internally. these pins can provide power to a usb hub if need be. i wanted to make it a female plug (i tend to favor female for sources and male for things that draw power, but **** gets mixed up), but didnt feel like cutting some breakaway headers down with my dremel.



opening it up to show the pi inside. it just sits on the bottom of the panels. it rests on the usb ports and the bottom of the card reader. i wanted to put some rubber feet in there but i couldnt find any in my junk boxes. i usually save stuff like that just for such an occasion. you can also see the power board here.



thats the top view. the design of this board puts most of the copper to work as a heat sink. the big fin sticking up in the back is also for heat dissipation. this was actually a peice of board trimming that still had a good layer of copper on it, so i soldered it to the heat sink portion of the board to dump a little extra heat. its a little crooked and warped and the soldering aint too pretty, but it was meant to get rid of heat, not look pretty.

the heat sink on the regulator is bolted to the board with some arctic silver 5 under it to help transfer heat better. even the screw and bolt have ac5 under them. to better transfer heat to the other side of the pcb. the big capacitor is crooked because i had to make a last minute substitution. i was going to use a shorter, fatter 1000 uf capacitor, but it was only rated for 6.5 volts. it takes at least 7 to get a steady 5v out the other end. so this was no good. i desoldered this 470uf cap from a mid 80s stereo board (the barrel jack was also taken from there) the switch was also a salvage item, though i cant remember from what. needless to say the pin spacing was not the same, and i had to solder new pins to the cap because the manufactuerer of the board i took it from clipped the leads too short, ****ers.

the only protection is a schottky diode which prevents reverse polarity. this thing probibly adds half a volt of drop and so is probably not the best choice. this kinda keeps the minimum input voltage at about 7.5 volts. which is a tenth of a volt higher than a nominal voltage for a 2 cell in series lithium battery pack. it works though. i could have used a pfet (according to afroman you can use one to save reverse polarity damage without a huge voltage drop or a fuse), but im a cheap bastard.

the layout is pretty basic lm7805 setup. the 100nf caps take out high frequency noise, big caps handle low frequency stuffs. so i get a nice filtered voltage. it doesnt need to be too clean because the pi has its own filters and regulators. though it does use the 5v line in a couple places on some of the chips. heres the other side:



all the actual wiring is on this side, the other side is all heat sink. you may notice the kitty in the corner, i cut that with an exacto knife while i was fixing all the holes with a sharpie before etching. i was actually supprised it came out of the chemical bath resembling its original form quite well. decided while populating the board to solder the leads directly to the traces on the board. rather than use the output connector. it looked better will help prevent power connection errors. the lead was clipped off of a front panel header in a long discarded computer case. i always save **** like this because im too cheap to buy modular housings, crimp pins and a crimper.

heres the internals without the power board installed. everything just floats around but the structure in the middle hovering a couple millimeters over the processor keeps the power board from touching the pi. and the heat fin keeps it from sliding out.



and with the power board in place. the board connects right to the gpio port underneath it.



i figure there is enough space for another small board. i might do a breakout for the spi/i2c interfaces, as you can support a large number of external bits of hardware with those and some programming. you can take a dual channel adc and a port expander and do a joystick entirely on the i2c bus. but yea, this is enough to get me started with basic stuffs. il see what else i can do with pi later on.
« Last Edit: September 10, 2012, 07:40:35 am by Nuke »
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN

 

Offline SpardaSon21

  • Hammered
  • 211
  • Posts: 2,213
    • Skype
    • Steam
Re: a slice of pi (pics yo)
Nuke, you're awesome.
17:37:02   Quanto: I want to have sexual intercourse with every space elf in existence
17:37:11   SpardaSon21: even the males?
17:37:22   Quanto: its not gay if its an elf

[21:51] <@Droid803> I now realize
[21:51] <@Droid803> this will be SLIIIIIGHTLY awkward
[21:51] <@Droid803> as this rich psychic girl will now be tsundere for a loli.
[21:51] <@Droid803> OH WELLL.

See what you're missing in #WoD and #Fsquest?

[07:57:32] <Caiaphas> inspired by HerraTohtori i built a supermaneuverable plane in ksp
[07:57:43] <Caiaphas> i just killed my pilots with a high-g maneuver
[07:58:19] <Caiaphas> apparently people can't take 20 gees for 5 continuous seconds
[08:00:11] <Caiaphas> the plane however performed admirably, and only crashed because it no longer had any guidance systems

 

Offline NGTM-1R

  • I reject your reality and substitute my own
  • 213
  • Posts: 9,545
  • Syndral Active. 0410.
Re: a slice of pi (pics yo)
Kitty!
"To those who truly harbor such fears, I can only say this: Let us look less to the sky to see what might fall; rather, let us look to each other...and rise."

IAR/Night Life/Life After Hayate/Wings To Fly

 

Offline Mongoose

  • Rikki-Tikki-Tavi
  • Global Moderator
  • 212
  • Posts: 6,494
  • This brain for rent.
    • Minecraft
    • Steam
    • Something
Re: a slice of pi (pics yo)
You are a mad, mad, mad genius.
Prepare for Descent...

 

Online Nuke

  • Ka-Boom!
  • 212
  • Posts: 6,718
  • Mutants Worship Me
Re: a slice of pi (pics yo)
despite all that copper heat sink im still having some overheat issues. heat buildup in the case was just sitting there and overheating the cpu. fortunately i found some smallish fans that can remedy the problem. lo and behold the screw pattern lined up perfectly to the peg holes in the studless parts with a 5lu (1 lego unit, or lu == 8mm) hole spacing. the fans were off of a memory cooler which didnt work worth a damn, seems they are 40mm fans with a 32mm screw pattern. this is good because i could just mount it with lego bits rather than just using a glue gun.

however the fan holes were too small and needed to be drilled out. unfortunately i didnt have a drill but i did have some drill bits i jacked from work awhile back. they were too big for my dremel, so i rotated them with a pair of pliers, and worked up the index until they were the same diameter as the typical lego axel. then it was just a matter of using said axels to attach the fan to a 5x7lu frame which attached fairly neatly. there was some noise but i had a silicone drive belt on my desk that made a perfect gasket, which also helps stop leakeage. and i had to plug all the holes with those little transparent dots you use as lights. pictures when i feel like it.
« Last Edit: September 12, 2012, 08:24:38 am by Nuke »
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN

 

Offline Klaustrophobia

  • 210
  • Posts: 1,455
  • the REAL Nuke of HLP
    • North Carolina Tigers
Re: a slice of pi (pics yo)
sooo.... what does it do?
I like to stare at the sun.

 

Offline Pred the Penguin

  • 210
  • Posts: 1,313
  • muahahaha...
    • Minecraft
    • EaWPR
Re: a slice of pi (pics yo)
Using Lego to build something like this... is awesome!

 

Online Nuke

  • Ka-Boom!
  • 212
  • Posts: 6,718
  • Mutants Worship Me
Re: a slice of pi (pics yo)
are you kidding? a lot of pi cases have been built out of legos. like this pi supercomputer. many other lego pi cases have been built. this is the first studless case ive ever seen though.

heres my now with cooling pi.



kinda ruins the look of the case though. i will probibly swap out the power supply with a smaller and less heat prone switch mode supply at some point, which will let me go back to the nice clean case design. on the flip side my pi runs more stable than it ever did. bluetooth even works sometimes. im connecting the fan to the battery header. i was debating whether or not to solder the fan to the leads after the switch instead, but decided that would be a mess and there is no place for the flyback diode that keeps the motor from frying electronics when turned off (this is actually in the connector under the heat shrink). not that the fan is being switched at all, but i dont want to fry anything.
« Last Edit: September 12, 2012, 06:37:20 pm by Nuke »
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN

 

Online Nuke

  • Ka-Boom!
  • 212
  • Posts: 6,718
  • Mutants Worship Me
Re: a slice of pi (pics yo)
sooo.... what does it do?

right now all it does is give me headaches (i hate linux!). i may try to get my wifi to work again so i can use the tv downstairs for a monitor. there has been some talk of porting freespace to the pi and other arm platforms, in which case it will be able to run freespace. i could also use it to replace the nxt brick in the picture. i have an i2c motor driver and an i2c servo controller i can connect to the thing. it will be like the nxt except i can ssh into it and with a web cam stream video back i suppose. of course id need to supply power at like 3 different voltages from a lipoly pack, with 2 5v rails and possibly a 12v rail for the monitor im using. i should open that screen and see what kind of regulator it uses so i can figure out what kind of power it really needs, and i would need a 7v rail for servos and a raw power rail for motors. but yea im not sure i want to do robotics with it.
« Last Edit: September 12, 2012, 06:49:32 pm by Nuke »
I can no longer sit back and allow communist infiltration, communist indoctrination, communist subversion, and the international communist conspiracy to sap and impurify all of our precious bodily fluids.

Nuke's Scripting SVN