Trying to leave the cube

So the fire has given pause for thought… I need to get out of my current job before I KO.

It’s a bit of an issue because I’ve worked in this company (a utility) for 7 years now and while I haven’t completely let my electronics skills atrophy, they aren’t at a 7 year electronics design engineers level. I’m trying to write a CV now but am feeling pretty overwhelmed.

Ideally I’d like to get into electronics design with a focus on robotics. After all, Mechatronics is what I studied and I think I quite enjoyed it. Anything with a bit of a physical element to it really. So far, my top career paths as I feel now would be doing something in the biomedical engineering field making prosthetics and human assistance devices or doing animatronics and prop building for the film industry.

I’m half staring at my unfinished CV just being frustrated at how I can’t seem to do anything with it. I’m just getting annoyed at myself


18 months on…

So it’s been 18 months since my last post. One would have thought that my beemo would have been finished by now. Alas, not. I’m a champion procrastinator so managed to not do ANYthing towards getting that dude up and running. some other guy did one though and it looks pretty cool:

I think I’d like to make mine still but yeah… the big news is that there was a fire.

a big fire

Pretty much everything is gone so I’m pretty much starting from scratch sort of 😦

Ok, not quite scratch – Insurance is gonna cover a bunch of stuff but yeah… I was hella underinsured so from fleet of 4 3d printers, I’m down to 1(which I bought after the fire)

IMG_20150426_180728 IMG_20150426_180804 IMG_20150426_180947 IMG_20150426_181010 IMG_20150426_181128 IMG_20150426_181134 IMG_20150503_151812 IMG_20150503_151806 IMG_20150426_180712

And the 5 volts returns.

So earlier, the lm7805 that I was using to power the pi just didn’t cut it cos it got ridiculously hot. so I changed to 3A rated 338 adjustable regulators as seen earlier.

I shoved all of the bits into the half completed body and everything works except the pi.

When I power it through the 5V regulator, it’s fine but when I try and power it off the 338, it doesn’t work.


I set the output at 5V and then did a bunch of test and just didn’t set it perfectly again so it’s sitting at 5.8V with no load.

As soon as I plug in the pi:

What the hell man. When I plug the pi into a 1A phone charger, it works. When I power it from the 12V battery through the 7805, it works. When I power it from my desktop power supply, it works – inrush current spikes to about 1.5A and then settles at around 600mA after a couple of seconds. When I power the pi through the 338 connected to the power supply, I get the same volt drop.

I must conclude then, that my 338 circuits are stuffed.

Back to the flipping 5V drawing board. Maybe I must have wired the 338s wrong. I get the same issue from both regulators so it must have been my crappy circuit. This looks pretty good I’ll give it a go and hopefully I’ll get something decent. OR…. I’ll try and come up with a switch mode power supply. This one looks doable: Either way I’ll have to go get the parts from somewhere. Maybe I should wait a couple of weeks and pick up the stuff I need for my Ultimaker heat bed at the same time…

Beemo doth sort of speaketh.

Audio Amp_01

That’s my audio amp circuit. I took the 3 from the last post and sort of butchered them and tried to find out what was going on while substituting components here and there. I chose the 14 pin package because apparently the heat dissipation is better because of the 6 extra paths to ground. I didn’t really find them to do that. There were the two components that made the most difference. The first is the 220uF cap on the bypass pin(pin 1) to ground. Without it, the chip was heating up a LOT. enough to burn you if you touched it. after inputting that, temperature dropped right down. I don’t know why. neither the datasheet nor application note help me out here but yeah, chip is cooler so w00t. number 2 is the cap between pin 2*3 – kills high frequency noise ruining everything. To be honest, i’m not sure exactly why it works and sounds good because it was a trial and error vibe but yeah, all good now.

And… stereo 🙂

I made a hole in the side of bmo for the pot which controls the volume:

What’s that Beemo, I can’t hear you…

Soooo, I gave up on supplying the 386 from 12V – didn’t even give it a go.
I popped to communica this morning(more like afternoon) and picked up some 14 pin LM380s and some pretty cool heatsinks. Not sure how I’m going to stick the heatsinks to the chips, but yeah, challenge for an older version of me.

I’m going to whack together something that resembles the following:
Which build by Chinese gambling cow staggers to stagger
Fortunately, amongst my “Harvested Parts” I found this pretty cool potentiometer – 10k. It’s a double pot – two seperate pots, controlled by the SAME knob. Aaaaaawww yeayaaah.
I guess it probably came from an stereo audio amp at some point too.
And so, into electronics we are born, within there, we die, only to be harvested and to rise from the dead, once again to fulfill our buzzlenatch.

To the Breadboard!

Don’t stop the Beemo.

After the whole LM7805 – getting too hot for my liking while powering the pi, I decided to use LM350s(adjustable regulators) which is rated at 3A as opposed to 1A. They didn’t have them at communica so I got lm338s(also adjustable) instead – these puppies go all the way up to 5A. I hope they don’t get as hot as the 05s but I’ve whacked on little heat sinks so with hope, it will be ok. If that doesn’t work, I might have to figure out some kind of switching power supply which might be a good idea anyway as there will be less power loss.
I’m going to test them out soon.

As for the Audio….
I found these little precision op amps which are often used for audio but alas, I didn’t read the spec properly. They’re spec’d to give about 325mW into an 8ohm load when powered by 6V which means at the 5V that I was giving, the little dudes were probably giving about 300mW and weren’t doing very well.
Reading that, I’ve just realised that I could have powered the 386 with 12 instead of 5(I checked the datasheet). That’s cool. That might push me up to 600mA which could solve the volume issue. This is if, I actually was supplying it from 5.
With that pretty cool thought, I will have a look and see if that helps.

3d printer

So a while ago, I got an Ultimaker 3d printer and figured I’d just drop a couple of pics in here.

So here’s the printer with one of my favourite printer – Bender Bending Rodrigues. I didn’t print it as one thing – it was a bunch of prints which I glued together later.



Obligatory Owl:

My housemate has a friend whose impeller on a pump broke so I took the old one, measured some of it and printed out a new one. I think it looks pretty similar and rate it should work. It hasn’t been tested yet though.

I found this cool Yoda – I was going to print out one of the yoda heads that’s all over the place but saw this and it was too cool.

Oh yes, stereo-typically, I have indeed printed out a naked lady. We all knew this would happen. I think she looks rather fetching, if a bit odd in orange.

Note to self – get more colours because orange doesn’t look very good.

Beemo the fourth(I think so, well pretty much anyway)

Woo Hoo:


Ye boi. So the body is coming together even though it’s part black and will be completed in orange. So I made a little power distribution module to take the batteries 12V and set it where it was needed.

So far the battery low, screen and the 5V regulator for the pi. I remembered though that I’ll need power for the audio amp because I figure the poor lm7805 is taking strain as it is, rather give separate power to the audio and take a bit of the load off. That said, I’m going to replace the 7805 circuit with an LM305 adjustable voltage regulator. This little baby can go all the way up to 3A which should mean it doesn’t heat up as much(I hope) I’m going to put on a heat sink anyway though.

So I got this little audio amplifier module from a while ago and figured… perfect opportunity.

Unfortunately, I can’t read so when I tried to test by plugging one speaker into it and then the headphone jack from my PC into it, the genius within didn’t look on the module and whacked 12 volts on the V+ pin and a slight pop sound and tiny spark happened, shortly after, a whiff of smoke rose up from the module.
Poopy pants. So there went the whole easy audio thing.
2 x 8ohm 3W speakers to be driven. Not sure how much power I’ll give them. Probably not so much because of the danger of a flat battery too soon. Anydoodle, I’ll have to build a 2 channel audio amp myself 🙂
Should be interesting and fun.

I’ve been getting annoyed with having to be so delicate with the PI and making sure when I put it down there’s nothing metal under it and that I don’t accidentally drop a bolt or spill some wine on it:

So once again, 3d printer to the rescue:

It didn’t fit perfectly into the base so I used a bit of force and the soldering iron to make a couple of tiny mods so that it got in there. I am not sure if it will ever be able to come out but it shouldn’t need to. The case came out ok but the top doesn’t quite fit properly. I think that maybe the heat from when I was using the iron to help make it fit must have warped the case a bit. I don’t think it’s too bad though. besides, this project has the case inside anyway. I’m much more concerned about beemo. I need to figure out a way to flatten his face nice and smooth.
I can’t take credit for the design of the case. I got it from here:
Thanks Buhi. I like this design because it’s minimalist and is just a perfect box for what I need. Very few openings so hopefully very little dust will get in there. I also really like the feet with screw holes. Perfect for my application.

I would rather not have downloaded it from thingiverse and would quite like to not have that link here but I must give credit where credit is due and for now at least, I can’t find another site to get designs from.

Here’s the box:



Beemo (3)

A more detailed schematic is below:

Beemo more detailed schematic_01

Poopy pants – I was printing out more body and my spool holder decided it’s about to fall apart so I’ve had to stop and print a new holder so that I can carry on printing without a disaster happening later. I’ve swapped out what was left of the black and am now doing orange 🙂

I’ve got a pretty simple but effective battery low indicator now which is pretty slick. I’ve breadboarded it and it works nicely to indicate at about 8V – the TFT starts freaking out at around 7ish. I’m going to use a nice super bright blue LED to indicate the battery low so you can’t miss it. It’s on the left below:
I still have to decide whether I’m going to allow play while the battery is charging or not – that’s why there’s an overvoltage protection block(still have to figure out circuit). I’d probably have a look at installing overcurrent somewhere now that I think about it.

The question is should I put all the AUX circuitry on one board or not. Nope – maybe one enclosure to make it neat but everything modular so I can swap stuff out if necessary to upgrade or repair later on.

So far, his black printed front with bits plastic welded together using a soldering iron:


Beemo Continued(1)

So I went and picked up a bunch of stuff:


So I got the screen from a place called TopCCTV it was about 700 bucks but I wanted it ASAP so didn’t go the dx or ebay route.
still need a few buttons and what not.
I’m still missing the following:
Turquoise plastic for the body(so I’m going to use black cos that’s what I have at the moment) My printer isn’t big enough to print the entire face at once so I’ve had to quarter it because it’s both too high and too wide.
Big red power button
Panel mount audio switcher(speakers til headphones are plugged in) – they showed me a panel mount and gave me a through hole :/
Battery low or charging or other indication, possibly just a pointless knob thing.
USB hub so I’ll have to feed the two pi inputs through the front and only have 2 usb ports for now.
SD card extender or SD card socket to make one
Network cable extender
I still have to make a 5V supply from a lm7805 and see if that will work to supply the pi but I think for the most part, that’s it.