Portable stereo speaker (digital amp) 5V 3-5W

I was never a fan of internal speakers on phones, even the best of them. the sound is always jarring and too strong in the 1-5kHz band. whilst they rarely can reproduce frequencies under 500Hz. and that is mainly due to the fact that physics is a harsh bitch (the size of the speaker and speaker box dictates the resonance range and hence power output at various frequencies).

So, what's a man to do? well that depends to the type of man. some go and buy a cheap compact speaker that sounds shite, some buy expensive ones (ex. Logitech UE series $100-$400) and live with what has been made for them, OR, he makes his own damn speakers! with all the features he wants and none of the nonsense he doesn't. 

[after 9 months of regular use]

So, here are my criteria:

Want

• Simple and robust
• Wired connection
• Potential for upgrades and add-ons
• USB rechargeable
• Long runtime
• Repairability
• Modular

Don't want

• Complication (fidgeting with bluetooth, pairing, hold buttons for on/off or functions, etc)
• Loads of controls that rarely get used
• Large or heavy
• Short battery life (high standby current)
• Heat management 

Our chip of choice is PAM8406, class-D amp with %90 efficiency and 3W Output at 10% THD with a 4Ω Load and 5V Power Supply. (originally I had made this with PAM8403, it turned out my parts could handle more so I upgraded).

Parts:

• ABS project box (ebay) ~$5
• Speakers (ebay) ~$5
• Amp module (ebay) ~$4
• Boost circuit (ebay) ~$1
• Battery li-ion 1000mAh (salvaged off rc toys)
• Caps 6.3V, 1500/1800µF x 14 low ESR (salvaged off old motherboards)
• Sockets, pot, leds, resistors (almost all salvaged)
• Wires (pc power supply quality cables - salvaged)
• Copper Heatsink (made of reclaimed metal)
• Paint, hot goop, cardboard, screws, etc (more or less free :D)

Notes:

• Battery has protection circuit on it
• Amp doesn't make enough heat to cause trouble with the battery underneath
• Boost circuit gets a bit toasty at full output (used what I had handy, needs upgrade)
• Panel could have been done cleaner, alas, "ain't nobody got time for that" :D
• Base funnel/tube was helpful but not hugely. according to online calculators, with my box size and the low frequency response I wanted, to achieve resonance, tube needed to be +60cm long. my box is 16cm long total soooo ¯\_(ツ)_/¯ 
• This speaker has much fuller sound than a phone speaker and gets much louder but it's no sub-woofer (physics being a bitch and stuff) lower band is around 200Hz before output starts to take a dive

Future upgrades

• Replace the battery with one 18650
• Swap the charger module with one that has micro usb (instead of mini) and has onboard battery protection 
• Redo the volume knob
• Redo the lights and light pipes

Locking hinge attachment for local bat rescuer

INTRO

So, this project started like this, I found the youtube channel of  this nice lady that was doing bat rescues. she would film some of the rescues and put them up for people to watch. It turned out she was local, and I offered to do a few potential upgrades. 

So, we have a collapsible net like the one here and the net is also on a telescopic extension arm. alas, bats having wings meant they often were hanging very high up trees or other structures. so the next natural thing was to attach this pole with some tape a longer pole, ideally an extendible one, ...or two. it turns out holding a small net on top of a wobbly pole 8-10 meter straight up in the air, while trying to catch a bat that doesn't take too kindly on the idea of getting caught could be a challenge. so some upgrades were in order.

First upgrade was to get a nice telescopic flag pole, a nice aluminium one that could do +6 meters. now she could tape the net extension to the flag pole and get another 2 meters of hight. less wobbly but still not all that great. so it would have been great to have a way of holding the net in an angle on top of the pole. like one of those gopro mounts, just stronger.

Also, it would need to hold the net frame directly, so , took the net frame thing out of a set with damaged extension and went brainstorming. after a few back and forths I had a basic idea to work on.
you can get an idea of the flag pole and the actual head here

STEEL?

So I did a prototype hinge, something solid and strong with quick lock and release capability. simple enough right? maybe...
This is the one I made, it's thin chromoly steel sheets, it's strong, it locks very very well, to the point I'm convinced it will break before it slips. aaaaaand it's heavy, way too heavy for the application. 200grams on top of a 8 meter lever means a LOT of force. oh well, I have like 5 different projects that can use a hinge like this, it won't go to waste. but we need something lighter, much lighter, and really didn't need to be that strong.

PVC PERHAPS?

I had some PVC tubes available but no other types of plastic sheets at the time. figured I do a prototype and see if I can make the same thing out of plastic. To get some sheets out of the pipe sections, I cut the PVC tubes lengthwise and unroll them with the help of a heat gun. Now to get really flat sheets I would sandwich each piece between two thick aluminium offcuts, clamp, and slowly heat till PVC would spread flat. then I could cool the whole thing down and extract my nice and flat plastic sheet. needed 12 of these.

Then made some patterns and cut out the hinge sections. also need to cut out some spacers. then used some more PVC tubes to make a body to hold the whole thing together. to lock it I wanted to use a quick release mechanism but had to forgo that in the interest of time. so used a wing nut and two wide washers to get a solid locking action. one side has a screw that attaches to the tip of the flag pole, the other side has a tight slide-fit to hold the net frame. 

It turned out quite solid in the whole 270 degrees of movements. but just for good measures I had made the hinge so it could be flipped around and at 270 degrees it would sit on the other piece directly and hence reduce the force on the hinge. while at it I made a fix attachment as well, just in case.

This prototype worked well for one rescue season, even got featured in some of the rescues. but alas, nothing goes "that smoothly". we had a record-hot summer and at one point the pole was left in the car in the sun with the net attached. the heat and added force was enough to deform the PVC. unsurprisingly, what can be heat-formed can also get heat-un-formed. oh well, maybe using metals wasn't a bad idea after all?

ALUMINIUM OR ALUMINUM?

In the past I had tried to source some aluminum with no success. I hear its only available in US and it's export is illegal. so, the next best thing was locally grown aluminium. 

Working with aluminium has some unique challenges, specially thin sheets of it. it's gummy, has tendency to "cold weld" and to weld it you need a TIG welder, and usually can't be heat-hardened. I had temporary access to a TIG welder so I decided to give it a go. maybe I could make it work with some additional tricks.

aaaaand...., NOPE. aside from welding it and doing some weld build-up which was a pain, the heat as expected annealed aluminium even softer and more prone to cold-welding. even after lapping the hinge in, it was not as free moving, and perhaps worse, if I were to bring the parts together without loads of oil or silicone lube, the layers would stick like crazy and just gull the surfaces pretty badly. I knew this was a long-shot, just didn't knew how much of a long-shot..... so, on third thought, maybe plastics were a reasonable solution after all...

POLYCARBONATE (PC)

So, need a plastic that is not gummy (like PE or PP), not weak or heat sensitive (like PS or ABS), easy to source as sheet for me (unlike POM or PTFE) and it needed to be though. very few non-exotic plastics are left to chose from and polycarbonate was the obvious choice. aside from one minor caveat of requiring DCM for fusion welding. DCM being a bit of a controlled solvent, is hard to buy. I could have extracted it out of paint stripper but that requires some glassware that I don't have and rather not get at this point. so, no gluing, at least I can do some minor heat forming. 

Bought a small sheet of 4mm polycarbonate and did the usual cut-outs and drilling, and sanding. not bad!, looks promising I thought.... so, let's go further.

A thin steel sheath and a bit of sanding, heating and some epoxy to fill all the gaps... damn it! now that I have epoxy on it, it's not going in. (that's what she said...). some cursing later I got it in and it looks good! I mean I have epoxy all over but that cleans easy enough.

I wonder what these few odd looking marks are though?

.....FUCK, are these cracks? yeah, yeah they are cracks..... FUUUUU....*flips-tha-table

Ok, so, it's two weeks later and I'm cooled down enough to get back on this. kinda out of ideas though. I wish I had my furnace going, maybe I could cast something. or maybe I do something with fibreglass casting? I don't have the right tools for casting of any sort at this point..... perhaps I should give polycarbonate another chance...

Archery Target Frame build and Target Core repair

= Disclaimer =
This is not a tutorial nor a step by step guide. this article is meant for clubs, experienced archers and makers as reference material.

Alright, so, our club bought some new targets and the old ones had to go. the cores were pretty much gone but the outer circle was still usable.

I salvaged some high density foam from another old target and used gel contact cement and a brush to apply it to each layer as I rolled the foam. having someone around as an extra hand in this step will help you a lot as you need to roll the foam pretty tight and foam will fight you back :) once rolled to size (just about a centimetre oversize actually to get a snug fit) tied it up with a few straps tightly and let it sit to dry for a week or so. core goes in as you see here.


In the meantime I went about making the frame/stand for the target, I used 4.5cm x 7cm treated pine and a sheet of 9mm marine grade plywood. I used galvanised hardware, if you can spare the cost go for stainless. 

This is the plan and dimensions I took off of club frames. keep in mind to get the target centre height right (for competition standards) for different targets you may need to modify the height a little.

Three items that are not shown here are ground anchors:
Target needs to get tied tightly to the frame, we tie the targets to frame by a piece of rope and using the four rope loops you see on the target, from the back tied ropes would look like a plus sign.

To reduce the risk of target toppling over when people are pulling arrows we always anchor our targets with a 4m rope from the top of the frame on the back side to the ground with a large (40cm x 12mm) peg. the peg needs to go to the ground in an angle pointing away from the frame to support the rope properly.

Lastly, we had eye bolts on the lower side of the legs to peg the frame to the ground directly if need be. we rarely needed to use those though.


As for the rest of hardware bits used:
Bolts for the hinges on the top of the frame
I used 2 long bolts with 2 nuts and 3 large washers each.
They go on like this:
bolt head > washer > timber > washer > timber > washer > nut > nut

The main idea here is to have a washer between the timbers to let them slide easily and act as a hinge.
As for 2 nuts that go on each bolt, the first one is the nut and the second one acts as a lock nut, you need to put the first nut in and move it to where you need it, then hold that nut with a wrench and tighten the second nut onto the first, that would lock them in place.
Obviously there are other ways of doing this as well.
 
For the target support bars I used 2x50cm pieces of medium duty 2cm x2cm square tubing. they were attached by 3x7cm roofing screws each , 2 to the side and one to the top.

In this case I didn't need the bars to be removable, if you need them removable (so you can easily put it in storage) then you got to make a pocket with a larger steel tube to accept the support bar. you also need a pin or similar solution to hold the bar in place, you do not want the bars to move on you or fall off. target itself weights over 30kg, the frame is not much lighter either.

As for the rest of screws, Used a bunch of 4cm chipboard screws to attach the plywood to the frame, those plywood triangles help a lot with making the frame rigid.

Also a bunch of 15cm self drilling Bugle Head Batten Timber Screws to screw the frame timber itself together, 2 for each joint. these are a bit overkill but they were needed since I didn't want to use any fancy wood joining techniques or wood glue.

=====>> Source files are here <<=====

And here are some additional pictures of the build for reference.

Update:

2 years on in the open and no sign of wear on the frame

Kitchen Island? "yes, we can!"

So, decided to make a hardwood (merbau) kitchen table/island for additional storage and work surface, because why the hell not! :p . garage wasn't the best work space but at the end it worked out.
I can't be bothered with drawing a model of it as it's already done but if you want information or a model drop me a line, I should be able to put something together. (this table is made from off the shelf items sold at  Bunnings)

UPDATE:

Now there are two of these in existence and the original is holding up great after almost 3 years :p