blinking badge - circuit simplicity

The other question that came up when discussing the badge was how simple it should be. William suggested that instead of going with a led that has the blink built in we put in the needed circuitry (555 timer, caps, etc) ourselves.

My gut reaction is to go with the design I envisioned (surprise), just a single two lead RGB LED with the flash already built in and a battery. is the set I ordered for testing. My reasons are as follows:

  1. The simplest possible thing to have someone solder. 4 solder joints and the novice has a working device.

  2. Less poking through to mar the front of the device. Just two connections from the battery holder (0 if we find a cheap, easy to solder SMT battery clip) sticking out of the front.

  3. probably cheaper.

  4. to get the same effect (different colors, not just a blinking red) with through hole components (see point 1) would possibly be bulky.

One reason a more complex design might be desirable would be to provide a greater challenge for older or slightly experienced solderers. Particularly for people wanting to dabble with soldering SMT components.

If there is a strong desire for this, perhaps the device could be designed to do double duty, incorporating the minimalist circuit I described with the RGB LED in the middle, plus all the traces needed to also mount SMT components to drive some optional blinking LEDs elsewhere.

That way the same board could be used for novice and more advanced classes.

The risks I see with that approach are:

  1. confusing to the student . i.e. “oh, ignore that stuff, that’s for something else.”

  2. size bloat or…

  3. too hard because we chose tiny components.

Left to my own devices, I’ll be laying it out with just the battery and the LED. That being said, I welcome comments on this.

I’d put a LMwhatever temp sensor and an ATtiny on it too… pre-program the chips and have it do something useful like blink or flash brightness with temperature. Or maybe a MEMS microphone / piezo kinda deal to amplify heartbeat. Just an LED and battery is a little boring to me … Then again, I’m not the target audience. (He says while laying out a 4 layer board in another window…)

That’s a neat idea, but you have to consider the cost of materials when you make these. ATXHS’s boards are intentionally simple because simple is cheap.

My only concern with that is that it just has 4 solder joints. I guess that would be okay for a quick, high-turnover experience.

The 555 is pretty cool because it adds 8 joints.

The little digispark arduino clone is a neat little soldering project. It’s actually sort of intermediate because you really need to solder a shield at the same time to ensure the headers all line up. But you’d need a fair number of kits, and you’d probably have to have a deal with the manufacturer or charge $10 or more for the kit.

My gut says 4 is okay. It would be nice to have a project board (with through-hole vias) so people could do a few joints before actually making the blinky.


What’s your budget? How many do you see getting made? I deal with this stuff on a daily basis. I can never make it in for Tuesday meetings but I’m more than happy to help with design, manufacture, etc.

The other thing to consider is how long it might take to solder.

The fewer solder joins, the faster it would be to assemble and we can get more people through the class faster. Depending on how many people we have manning that booth, we could end up with a severe backup of people waiting to solder their gadget if it takes too long to solder.

I can contribute that the problem Paul’s talking about happens at ATXHS’s events, even with 3+ people at the booth and incredibly simple boards.

Excellent, the “where to get the board printed” step was a future question I was going to put out there and ask you (Dave) specifically. No budget was voted on, I’m just exploring the possibilities before putting it to a vote.

As someone who also usually misses the Tuesday meetings, I should have known to start out by explaining the project.

The idea is to have a nice stockpile of little “learn to solder” kits in the form of a badge with the hive13 logo and the phrase “I learned to solder from…”. The idea is that these are used in events like the mini-maker faire, either really cheap or free. The novice (including young children) get a quick lesson in soldering and then end up wearing an advertisement for the rest of the day.

It’s based on a very successful thing the ATXH (Austin hackerspace) does. You can see an early version of the ATX blinken bat at They use it for both outreach and to raise money.

Their current version uses magnets instead of pins, which is how I want to go.

They printed up 1000 of them and got the cost per board down to less than $0.50. I was thinking something in the realm of 1inch by 1.5 inches, or possibly 1.5 x 2.

Regarding time and crowding:

I spoke to Jim about this before the mini-maker fair meeting last week and he suggested that for this event (since space is free within reason) that we set up tables with stations in an area adjacent to the hive13 booth and have people sign up for classes on the hour or half hour. This would help with the crowding possibly.

Though if I’m manning the booth at other times and someone comes around and wants to learn to solder, I’d probably just go right ahead instead of making them wait.

For a “fancy board” my thoughts -

  1. use SMD AVR chips and most components
  2. use edge-connector port for programming
  3. pre-assemble everything except the through-hole stuff, perhaps let people choose color of LED they solder


I think for this circuit what the ATX space did is perfect. I don’t think we want people to be soldering in ICs if we just want to show them that they can solder. I can already see lots of people with ICs soldered in backwards!

Also with regards to the size: I would shop around and look for a place where the panel for maybe 200 (to start with?) isn’t going to be outrageously expensive. OSHpark has a medium run panel that is $1/sq inch so that is probably a good number to do estimations from.

I just had 500 boards that are 4.6 sq in each made for $1.51 from Advanced Circuits… As much as I try to support OSHpark, there are a lot of cheaper US-based options for medium quantity.

I had a proto board made by them once…I really was not impressed. The board had no silk screen and was almost transparent. It cost around $60 for 2 boards to be turned around in a few days. Now I get why it costs $60 for something like that but the quality was absolutely shit. They sent me a drink coaster that was a much better quality board. So I guess you only get decent stuff if you buy in bulk… which is bad marketing because I haven’t used them since…

Advanced Circuits 2 layer prototypes suck. They don’t have soldermask unless you pay extra, garbage service.

Their small-medium q. (50-1000) quick turn is damn near unbeatable.

Their small-medium q (50-1000) medium turn (i.e. 2-4 weeks) is fairly decent, especially for a North American board house.

Their large q (1000+) is decent for short-medium turn and horrible for value/long term.

Their 4 layer pricing isn’t that shabby.

For the stuff that is too small for a Oshpark LARGE run (i.e. 5000 sq in or so) and too big for the $1/sqin medium runs they fill a nice niche.

The board houses all have such different price structures, turn times, etc. that it really boils down to what you’re ordering.



This has been a good discussion. We can all applaud Marcus taking the
lead in this.

I'd ask Marcus to consider these inputs, and post a proposal as an
item of business by the July2 meeting date.

The proposal would be to authorize Marcus to make the HIVE's purchase
of a large batch quantity of simple boards and minimal components for
the HIVE's solder worktable at the October Maker Faire. The solder
mask would include the HIVE13 logo. We'd ask for a $1.00 or so
donation to cover the material costs to break even, more or less,
details to be in the proposal.


Clearly I lean towards the simple version and that’s the board I will be designing, but if we assume that both version of the board would be the same size, there is no reason we can’t figure out the price of the two versions keeping the board costs the same. I’ve created a google docs spreadsheet to track possible costs at Dave, if you could, please fill in the “advanced version” tab with any parts you envision we can use that for comparison. Be aware that the initial deadline would be to have a fairly large quantity on hand for the mini-maker fair in October, so any advanced design has to be debugged and completed by then. There’s no reason we can’t do an advanced version later, other than losing economies of scale.

Obviously we can’t get real quotes without the actual gerbers which require creating at least the outline of the board, but I’m going to try to start filling in guesses from various vendors. For example, I took the "500 4.6 sq in boards for $1.51 each " figure Dave had for advanced circuits and plugged that in for 1000 quantity. This is an area I could use the input of everyone (like Dave) with experience ordering larger quantities. I only have experience getting boards from batch places like batchPCB, OSHpark and seeedstudio.

I’m making the assumption for now that the board is 3 square inches. It would be nice to have a few frills like a yellow solder mask and a black board, and a non rectangular shape. I’m thinking the bottom would follow the contours of the hexes, with space above the logo for the “I learned to solder from…” text. I know that some places charge extra to funkify the the borders, others do not.

It is very likely I will not be able to make the July 2 meeting, but maybe we can kick around some possible budgets tonight to get a rough idea of what we might want to spend and I can have a proposal written up that you guys can vote on in my absence on the 2nd.

Marcus, I won’t be at the meeting tonight. Keep me in the loop about what the group decides.

If we end up deciding to just to a small (100 or so) run of boards, I’m inclined to just go with the simple version. It would be nice if all that’s visible on the back are the outline of the battery, some helpful text like “long wire goes here -->”, and potentially a blurb for oshpark. But…

Here is how I propose we handle the “both simple circuit and complex version on the same board” development.

Once we are happy with the simple design, I’ll share it and and those interested in doing something more with it can hack at it. We’ll define the following design constraints:

  1. The battery stays about where it is, because the badge will be held on by a magnet sticking to the battery, and we don’t want it hanging funny.

  2. The traces to the LED be routed to provide maximum real estate elsewhere.

  3. The power trace between the battery positive and the annode has a pair of pads connected by an exposed bit that is easy to cut to disable simple mode, and a couple of close together pads are nearby to provide a place to solder a jumper to provide power to all the advanced circuitry.

This assumes that the advanced version will actually run off of a single 3 volt CR2032 coin cell of course.

If the advanced design were to make use of a normal common cathode RGB LED in place of the two lead pre-blinking one for the simple design, we can just put a footprint with all four holes and maybe fill the two outer ones with solder for basic kits to discourage incorrect placement. I suspect that’s why these LEDs typically have the ground on one of the two middle pins, for backward compatibility.

Depending on where we decide to get it printed, we decide upon a due date. If the advanced board isn’t prototyped, debugged and ready to order in quantity by then, we go ahead with just the simple version. For example, if we go with OSH park for both the proto typing and the actual run, that deadline should be something like 3 weeks (full order) + 12 days (prototype run of the basic board) + 2 week buffer. So 47 days before October 19th, or September 2 would be the deadline.

Or maybe we just prototype the simple version earlier to make sure we have a fall back, and the deadline becomes 3 weeks +1 week buffer, or September 24.

There is of course, no reason why development for an advanced version couldn’t continue after the deadline, for a future run after we gauge demand.

As soon as you get a version of the simple one worked out that is going to be the same dimensions, email the board files. I’ll run with it to make an advanced one.