Death Burro part 4: them’s tha guts

this post will serve as the hardware manual for Death Burro for those that will own him soon, so they can continue where i leave off on the next version!

here was donkey yesterday, guts masked ready for a final coat of flat black to cover some scratches and what not. (Brady’s double ended light-saber in background does not come with the donkey.)



just a shell of his former (donkey) self

donkey has 8 Phillips head screws on his right side holding his guts in.



don’t remove the 6 small screws on his left side, these are holding the motherboard mounting risers and screen backing.



boy or girl?

access ports and what not on his underside – we’ve got a center hole for pooping and/or the 12v power cord. there’s also a single push button, a rotating knob, and a 2 amp circuit breaker.



some good stuff here – we’ve got 2 different colored LED bars in each ear. then there is the large touchscreen, no cheesy little dot matrix display, this is a full-color capacitive-touch-screen. And finally, look closely in the nostrils, oh yeah – frickin laser beams attached to his head.



it’s cold robot heart (and other guts)

here’s the entire gut-shot.



by the numbers…

(numbers reference the photo below)

  1. the main external interfaces. power comes from the external 12v switching power supply (wall wart) and through the 2 amp circuit breaker. a single push-button switch and an rotary encoder are also accessible here and are both direct inputs to the main computer. the rotary encoder currently acts as a volume control, but could be programmed for anything. the button currently switches from main screen to config screen, but again could be programmed for whatever.
  2. the main 12v breakout. the bottom half is ground and the top half is positive.
  3. the 5v DC-DC converter. this power supply converts the 12v needed for the lights and perhaps future accessories to the 5v need by the main computer, the USB hub, and the lasers. there’s also a 3.3v system within the main computer, so in total we’ve got 3 complete voltage subsystems.
  4. the breakout for the 5v system. inputs to this board are the 5v power coming from #3 and a 12v relay input. the board splits the always-on 5v power to the main computer and USB hub. it also splits off a relay-switched 5v output to send to the lasers.
  5. the main hardware output interface from the computer. this board has an IC that takes a variety of voltages, as 2 high or low inputs and safely isolates those from 2 relay-switched outputs. i’m using 2 GPIO pins from the main computer to output a +3.3v high to this board, which in turn switches it’s (2) 12v relays on. the relays control 2 different circuits, one being red LEDs and the lasers, and the other being blue LEDs. these 2 circuits will be used to identify 2 different types of msgs that the donkey will respond to. i was originally going to use a couple solid state switching circuits, but FRY’s Electronics happen to have this ready-to-solder kit handy for $15 which included the screw-down risers, so it was an easy choice.
  6. mini powered USB hub. 6a is normally plugged in here (removed to see below it, note picture before this one), and is the uplink from to the main computer’s USB port. 6b is also normally plugged in and is the cord to the WiFi module. the hub has 3 more ports on top that are available to run whatever accessories are desired (cables can be run out of his mouth easily from here.)
  7. mini ported speaker box and high quality speaker produces decent sound from a small package.
  8. can barely be seen, but this is the output cable from the main computer. the ground wire plus the 2 GPIO pins are already connected to #5, but 1 additional GPIO pin remains unused and a complete unused I2C interface breakout is here as well. the I2C is probably the simplest way to extend the donkey, including possibly making him robotic. shops like JeeLabs and SparkFun carry a ton of I2C addressable input/output modules.
  9. a couple bendable white LED strips provide some light for the donkey whenever it’s plugged in. i had these laying around already and just had to buy some clear heat-shrink to insulate them from everything else.
  10. (number not shown) some balsa wood glued to the donkey is the mounting point for everything, it insulates the connectors on the bottom of each circuit board and was easy to work with and cheap.


(numbers again reference the photo below)

  1. the USB wireless module and antenna is disguised with the mane.
  2. the main computer board. inputs for the push-button switch and rotary encoder, and the output for the speaker are on the bottom. 2 pieces of angle-cut balsa wood act as mounting risers to hold the board where it needed to be in order to connect the short ribbon cable to from the screen. on top of the board is a microphone input connector, the screen connector, and an 3 pin connector that can be used for battery power at some future point if the donkey is made mobile (more info on that to come). the power and usb connectors are on the back edge of the board.
  3. access hole was cut into the snout here and a red LED bar was added to the top to light up the area, and 2 red lasers were glued into the nostrils. the lasers are you’re typical little red laser pointer, these ones actually came from Walgreens and were supposed to be pet toys. getting them apart was a PITA, once i managed to hammer the main circuits out of the “pen” without damaging them, i then cut out the switch, and soldered leads to the main circuit board. i then had to heat-shrink each assembly because they had a positive-ground system and much of the metal on them would have shorted out. getting them inside the snout and glued to point out was also a PITA!
  4. this is the back of the touchscreen. 2 small screws at the top, and 2 larger screws from the left outside of the donkey hold this metal backing plate on which holds the screen in. here i had to cutup the original screen bezel into a small frame, glue that into the donkey, then paint it all black.
  5. a red and a blue LED bar will provide light that should shine out the main screened hole in donkey’s head when lit.
  6. holes were drilled upward into the donkey ears, and then as i showed last time, screen was glued to form a cavity in each ear. a red and a blue LED bar exists in each ear. and the right ear also has a microphone glued in. the microphone isn’t going to be used in version 1.0, but is accessible by the main computer and so some new feature could be programmed at any point to make use of it.
  7. to the left and right of #7 are some clear heat-shrinked circuits inline with some black/red wires. these are LED blinker circuits as all of the “status” (red/blue) leds are setup to blink when these circuits are triggered by the main relays on the output breakout board.
  8. this wire is a radio antenna, it will be left sitting in the donkeys mouth as it’s useless inside the metal chassis and would need to be unfurled outside the donkey to pick up anything.


all buttoned up

plugged in, but with the main computer (and screen) turned off, you can see the always-on white led strips glowing out from several places.



i may add one more white LED strip closer to the top so that the top hole lights up better, but i don’t want it to wash out the other internal red/blue LED bars, so we’ll see. he does make a good night-light (probably not for children, as it really does look like some scary-ass robo-alien-zombie-donkey has come to eat your brain in the middle of the night.)



i’m left with one final step, the software. something has to make this thing do more than have wires and white light. i’ve barely started, but have most of the core architecture figured out already. stayed tuned for part 5, where i’ll explain the software and should have a fully working donkey to show video of. and of course i’ll have to say goodbye then and hand the burro over to Aimee’s dev team.


see the rest of the build here as it progresses:

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