Public Radio progress

The latest rev (v1.1) of The Public Radio:

The current state is: 

• Arduino Pro Mini
• Si4703 breakout
• Mono audio amp breakout
• VREG
• A bunch of screw terminals

The next rev will be a little PCB that the Pro Mini can mount to, and on the back will be all discrete components comprising our own FM tuner & amplifier. This will reduce the cost of the assembly by a *lot* (these Sparkfun boards are easy to work with but silly expensive), and will allow us to play with the circuits a bit. 

The incredible thing is really how cheap the Pro Mini is. These things cost under $9 (cheaper on eBay) and have a lot more features than we'd ever need. Eventually we'll strip that off too and run the whole thing off of an ATTiny (or similar) but for now there's no point in getting ahead of ourselves - the Pro Mini is cheap enough and requires very little work on our part to get our MVP out quickly.

We should have the updated circuit done tomorrow and will be working on board layouts over the weekend :)

Dance dance

Zach + The Public Radio.

He *says* he prefers WNYC, but I know the truth :)

Schematic & Plans

One more report from our Hacknight: The Public Radio's schematic.

We'll use a Pro Mini for this next rev (the one after that will likely get an ATTiny), but will be using discrete ICs for both the FM receiver chip (Si4703 for this rev, though we'll eventually transition to Si4702 as we're not using the RDS features the 4703 offers) and the amplifier.

This schematic got a little sloppy at the end (after all, I was drawing it :/). I'll probably redraw it once more on paper just to make it pretty, and then we'll punch it down into Eagle and build a board file off of it.

There are probably a few mistakes here so if anyone's got a sharp eye, let me know :)

And lastly, our tasklist for the next few days: 

Most of this doesn't bear much comment... The next rev will likely get laser cut acrylic lids, which I kind of hate but which should be significantly more economical (and quicker to procure). Eventually we'll do stamped stainless steel lids, but that's a ways off. We also need to do a bit more digging on active antennas, as the telescoping RC antennas we're using here leave much to be desired. We've also got to look into other wire-to-board connection options; the screw terminals we're using (.1 spaced) are still a bit bulky, and we'd really like to avoid soldering wire directly to the PCB... 

More soon.

The Public Radio assembly

A few days ago Zach and I assembled the lids on the newest version of The Public Radio. 

I had spent a bit of time thinking of how we'd streamline the process, and had purchased a round punch and some foam tape to make an adhesive backed spacer for the speaker. For production we'll get these die cut by a job shop, but for prototyping this worked very well.

I was trying out two different varieties of mounting screws for this version. In order to make the lid cost effective, I designed it with countersunk thru holes and am mounting the speaker from above. That meant finding screws that would bite into the plastic speaker body well, and I bought a selection of thread-forming screws for that purpose. They've got cute little torx heads which - if I spend a little more time organizing the speaker perforations - will look pretty nice on a stamped (as opposed to this SLA printed) stainless steel lids.

Overall, the assembly worked very well. Honestly I'd prefer to nix the screws, but that's impractical... it's possible that I would design the lids in two parts (like a clamshell) instead, so that the mounting hardware could be hidden from view.  We'll see :)

We should be receiving new PCBs on Monday, and will be assembling a few v1.1s ASAP. Expect updates.

IRL Crowdfunding

Every few days someone asks me about one of the projects I'm working on. Most often they've seen something I've put up on Instagram or Facebook, but didn't have enough context to really understand what it is I'm working on or even whether it's for sale.

Most of my projects will eventually be crowdfunded, and I expect to be able to convert some of the folks who I've talked to during development. But I had a thought the other day: Why not start taking orders immediately, whenever someone asks? 

The thought is this: If you ask me about The Public Radio, I'll give you my little pitch and then (assuming you've acted enthusiastic) ask for $20, cash, now. I'll then whip out my phone and email you an informal receipt, and will deliver you a v1.0 when it ships (probably the pre-Kickstarter version). 

This would help me in a few ways. First, it locks in a customer. Second, it lets me know whether I'm actually onto something - if everyone says "no," then maybe I should pivot. Third, it gives me a little cash to help keep the project moving forward. And I can be pretty sure that you'll ask me about the project status in the future, which is the most thrilling parts of building a product like this.

I think this is a decent idea. If you're reading this, ask me about what I've been working on the next time you see me - we'll see how it works :)

In the jar

When we started The Public Radio, we planned on making it look sleek and functional. My design aesthetic tends towards midcentury modern, and brushed aluminum is kind of the standard bearer for that class of objects. But after an hour or two of talking, we realized that the type of customer that we wanted to appeal to would probably never pay the kind of pricetag we'd need to charge for the product we wanted to build.

Plus: If cuteness allows you to be effective, maybe you should get over yourself and just do it.

So it's a radio in a Mason jar. It's cute, and it allowed us to iterate quickly and inexpensively.

A few months ago, I put an MVP together (an iPod + a simple amp) and threw it in a jar with a speaker. Since then, The Public Radio has been mostly an idea, or at best a breadboarded, hacked-together mess of wire. While cool to the two of us, it hasn't been much to look at - iPhone headphones and all.

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Over the past few weeks, I've gotten the lid design & potentiometer figured out. Meanwhile, each of us has been learning about register addresses & trying to strip our firmware of everything unnecessary. So yesterday, after much ado, we finally wired up the switch and speaker to the rest of the ratsnest and got the thing mocked up.

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Quickly, then, the goal was to get it into the jar right away. So a bit of protoboard and a little more fiddling, and we were able to squeeze it in.

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To backtrack a bit: It's worth noting that our current state - an Arduino Pro Mini and a couple of Sparkfun breakout boards - is a step backwards from where we were a few months ago. If you'll recall, there was a time that we were putting discrete components on our own PCB. But we had a few issues with our circuit design, and regardless we realized that we had aimed too high on our MVP. So we went back to off-the-shelf components and protoboard, with the intention of doing some basic product validation. Which I dare say we're getting close to.

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The next step here is to make a few more of these things and start showing them off. I made some revisions to the lid the other day, and Zach has already ordered a new custom PCB (basically a breakout board with a few screw terminals on it) that'll replace the protoboard here.

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We'll have three of these, plus a few more speakers & pots, in the next week or so. In the meantime we've been scheming about the next steps: having the lids die cut out of brushed stainless steel; getting rid of the Arduino and building the radio out of a ATtiny + the Si4702 + a class-D amp; world domination, etc. 

It's hard not to get ahead of yourself sometimes, but I prefer to keep my mind at a point where I'm aware of which questions to ask just before I need to ask them :)

Short!

The Public Radio is now shorter :)

We've been working on fitting everything into the next size down jar for a little while, and this afternoon we made a few steps in that direction. To celebrate, I spent a few hours modeling the target jar. 

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The previous model was one of my first surface models, and I hacked it together *hard.* In the meantime I've gotten a lot more experience with NURBS, and it was great banging this out quickly. It's a lot more realistic in many ways, though I did half-ass the Ball logo a bit.

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On the electronics front, Zach cranked out a new board design and we should be ordering a new PCB tomorrow. I also ordered new lids (one based on the new design, which is heading in the direction of sheet metal stamping). Meanwhile we've got a breadboarded version running, though it's a bit unwieldy. 

Expect more in the next week.

Public Radio Progress

More on the electronics side soon (we had some good progress today), but for now just a few images.

I spent a bit of time today remodeling the lid to account for a few slight changes. The real rationale has to do with the potentiometer, which needed to be reoriented slightly. In the meantime I laid the speaker holes out a bit differently, and I'm pleased with the result.

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I hope to have the whole thing together & in a jar by the middle of this coming week - finally! 

Currently

My desk, working, at the end of the day.

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Oh - as I had been hoping, The Public Radio *should* fit in this super cute 250mL jar :)

Switch

This is *so* satisfying.

:)

Potentiometers

Today is potentiometerday.

The Public Radio has one knob on it: a switched single-gang potentiometer. The switch turns the entire device on, and the pot adjusts volume.

The plan originally was to get a PCB mount pot, and hang all of the electronics on it. That ended up causing troubles re: fitting everything into the jar, though, so we changed directions a bit. At the moment, the goal is to find a pot with solder lugs. It'll be panel-mounted to the lid of the radio, and will have five wires going from it down to the circuit board. My hope is that this isn't *too* labor intensive to assemble... we'll see soon. 

Ideally, we'd be using a 10k pot with a logarithmic (audio) taper. The theory goes that the human ear has a logarithmic response to sound pressure, and so audio should be controlled along a logarithmic curve. From a great article called "The Secret Life of Pots":

Volume controls are different. The human ear does not respond linearly to loudness. It responds to the logarithm of loudness. That means that for a sound to seem twice as loud, it has to be almost ten times the actual change in air pressure. For us to have a control pot that seems to make a linear change in loudness per unit of rotation, the control must compensate for the human ear's oddity and supply ever-increasing amounts of signal per unit rotation. This compensating resistance taper is accurately called a "left hand logarithmic taper" but for historical reasons has been called an audio or log pot. In these pots, the wiper traverses resistance very slowly at first, then faster as the rotation increases. The actual curve looks exponential if you plot resistance or voltage division ratios per unit of rotation.

As it turns out, finding a logarithmic pot in the configuration I want is rather difficult. I spent a while searching and ended up buying a little selection of pots - some linear and some logarithmic; some PC pin and some solder lugs; with various shaft conditions and body styles. I tried them all out, testing for knobfeel and comparing price, availability, and usability. The results were interesting, and to my delight the pot that I liked best ended up also being one of the least expensive and most readily available. It's a 10K linear taper with a 6mm flatted shaft and solder lugs.

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In the background you can see the knob that I'm planning on using. It attaches to the shaft of the pot with a little set screw; the result is quite pleasant.

A geeky note: I really like looking at switch designs, and this one is super simple and rather clever. On the backside of the pot there's a tiny cam which actuates a little spring-loaded contact. The whole operation is totally visible and rather mesmerizing. 

As I noted, this pot has a linear taper. It's likely that, after some testing, we'll add a resistor between the wiper and the counterclockwise lug, making the nearly logarithmic. This is done through a simple and really effective algebra trick, which is described really well at the same "The Secret Life of Pots" post. More on this as we get the rest of the radio together, likely in the middle of next week.

Public Radio hardware

For a variety of reasons, the Public Radio was due for a complete hardware redesign (the potentiometer wasn't fitting, and so a smaller speaker was required... etc.). I got that mostly done this afternoon - modeled the new speaker and a knob, and redesigned the lid to fit them.

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I'm not totally sure how I feel about the grille design, and if I had to bet I'd say it'll change soon. I'm also curious whether we can fit everything in the next size smaller jar, which is the same footprint but half the volume and *really* cute. Previously, we chose this jar so that a deeper speaker could be used, but the one we're planning for now is tiny - despite its good power output.

I'm hoping to get this new lid printed and delivered next week, which is about when the electronics should be coming together. Stay tuned.

Update: The Public Radio

I'm not going to go into the details here - it'll be posted on the Public Radio Tumblr soon - but Zach and I have spent a bit of time reconfiguring our MVP in the past week. The result should be done next week (pending a new 3D printed lid prototype, etc) and will cover all of the functionality of the end product. Right now it's a protoboard, an Arduino Pro Mini, and a couple of (meh) Sparkfun boards.

The shitty thing is finding a potentiometer that will work well. It should be a 10K pot, logarithmic (audio) taper, with a switch. Unless I'm missing some hidden trove, there are about 7 parts in the world that fit those criteria and are stocked in quantities of more than a dozen. And then 5 of those have PC pins, when I think I'll end up needing solder lugs... it's a huge PITA. 

Anyway, the project is moving along. More updates soon.

Progress: The Public Radio

Last night, Zach and I bribed Todd to help us jumpstart The Public Radio a bit. When we last worked on it, we had a short on the 3.3v line that we couldn't find. Well, that was fixed in short order, and we also were able to diagnose & fix a few other issues that we weren't aware of. 

We left with a board that's still not quite ready, but it's getting a lot closer. We also had a few more thoughts about how we should be proceeding, and it seems likely that they'll brew into something more actionable in the coming weeks.

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It seems likely that with another day's work, we could get this board tuned up and blasting HOT97 like it should be. At that point, though, we need to undertake a total redesign of the whole assembly. The PCB is the wrong size & shape; the speaker is too large; the potentiometer isn't long enough; the lid is the wrong thickness (and, ultimately, the wrong material). 

It's also seeming likely that we end up redesigning the radio to be a simpler (and possibly analog) device... but that will only happen further down the line.

by way of explanation: What is The Public Radio?

Yeah, I guess I never really explained it:

The Public Radio is a product idea for a single-band FM radio.  The unit will come packaged in a Ball jar and have only one control - an switched potentiometer that turns the device on and then changes output volume.  The consumer would purchase the device tuned to the local FM station that they regularly listen to: for me, it'd be either WNYC or Hot97.  Once you buy the device, it will *only* listen to that station.  It runs off a 9v battery and is easily transportable, stylish, etc.

(The pitch, as it were, is this: The idea that FM is a medium where you browse channels is totally outdated.  If you want to find new content, just turn on your computer.  With FM, the new mode is going to be to use it more like Pandora: You trust your content provider to play stuff that you like.  So you buy the Public Radio tuned to the channel that you have a relationship with, and the Public Radio is your permanent link to that station.)

Anyway, it's a fun project that Zach and I have been working on for the past few months.  I've been doing the hardware development, and Zach (whose electronics chops are much stronger than mine) has been doing the circuit design.  Right now we really need to get our PCB assembled (which requires a few tools that should be arriving later this week), and then I need to redesign the lid (wants to be brushed stainless steel, probably) and select a slightly smaller speaker.  Hopefully it'll come together in the next month or so.

public radio progress

Zach and i had a short worksession tonight and made a *little* progress laying out the first version of the Public Radio PCB.   

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a few mistakes were made - we need to organize our tooling a bit, and much of the layout will be done with solder paste and a hot plate - but we wanted to get something physical done and accomplished that wonderfully. 

we should get some more supplies in later this week and hope to make some real progress next week sometime.  slowly but surely... 

public radio pcb v0.1

kudos to Zach: a week or so ago, our first Public Radio pcbs arrived.   

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we've both been swamped with other things since then, but i'm hoping that we can get one built up in the next week or so.  more updates soon.

user story: the Public Radio

as a guy, i want a simple on/off function, so that i can turn my radio on easily when i'm shaving and have shit on my hands.

acceptance test: there's only one knob on the radio, and when i turn it clockwise, there's a tactile "click" and then the radio comes on to whatever station i have it preset at.

the public radio progress/mvp

last week.  some real text is sorely needed at this point, but it'll have to wait for now :( 

anyway, we're making some real progress.  the physical enclosure is mocked up and we've got a good acoustic test going.  we should have the actual amp mocked up in a few days, and will be working on the rest in the coming week or two. 

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pictured: my feet, coffee, etc.  obv. 

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pictured: the workstation, i.e. my kitchen's #2 counter/storage space.  the soldering station is defective and needs to be replaced; the amp is a piece of junk (and was put together wrong - my bad).  i just got a positioning jig to hold PCBs while assembling (the cardboard and spools didn't work all that well).  and... mamoun's hot sauce remains kinda inedible.

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pretty mvp.  and pretty cool.

the mvp is an off-the-shelf amp circuit, an ipod, and a speaker (the volume potentiometer isn't connected to anything), housed in a mason jar.  it sounds pretty great, though it's tough to change tracks/channels on the ipod.  luckily that won't be an issue on v1.0, which will have a fixed band FM tuner only. 

workday

good workday today with zach.  lotta progress, lotta dogs.  my surface creation skills are pushing up.   progress below, shown chronologically.  

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​what my shit looked like last night.

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​sometimes, dogs just follow the team around.

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​sometimes, dogs just hang out.

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​sometimes, dogs are like "what's up??!??!!"

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​fucked with the ring a bunch, and added the battery, but a bunch of the work happened on the "ball" logo, which has been a real challenge to nail down.  it still isn't perfect, and i needed to mess with the shape of the jar to get the logo where it is now, but i did get rid of a bunch of the workarounds that i implemented yesterday, and the overall model is pretty damn good.

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​...aaaand, zach's got the start of a layout going.  pretty cool.