Title: Event Badge
Class Size: varies (1-240+ over a weekend)
Cost: Usually done for donations/gratis. Kit cost is < $1. Mostly serves as a promotional tool.
Pre-requisites: none
Minimum Age: 8-10 and up (under 18 must have parent present)
This is the simple badge we usually teach people to solder with at events such as IngenuityFest and Maker Faires.
History: Originally, we sourced the Makezine robot badges when they offered good bulk discounts. At some point, they stopped offering good bulk discounts and their stock became harder to source. We then switched to getting knockoffs of the robot badge via eBay and swapping out their default red LEDs with color changers. That persisted for a few years, and then for the 2017(?) Brite Winter, we (Sam w/some input from Bob McT) ended up designing what became the Rocket Badge. For the 2023 IngenuityFest, we updated the badge shape to a lighthouse (to match the one in IngenuityLabs), and added the ability to use an external battery pack and 3d printed stand.
Rocket/Lighthouse badge Requirements:
- As Cheap As Possible, but still reliable to build (sub-$1 for the entire kit)
- Hard to mess up (though it still happens from time to time!)
- Actually include our URL/Name and not advertise for somebody else…
Parts:
- PCB - Designed a custom PCB in Eagle. Original prototype test run through OSHPark, full runs from JLCPCB.
- Battery clip - CR1220 clips (Keystone 3001) from Mouser/Digikey/Newark, whoever's cheaper in bulk. This is the most expensive part of the kit. A much cheaper one can be sourced from Aliexpress, but it's flimsy and more fiddly to solder.
- Pin & Pinback - Get these a few hundred at a time from eBay. Pins usually have some kind of extra tack on them (like an anti-rotation tab on a pot?) that I usually have to remove ahead of time.
- Currently (2023) experimenting with some small brass nails instead of pins.
- RGB blinking LED - buy them by the 100 on eBay. Some flash fast, but we usually get the slow ones.
- Battery - CR1220. Buy in bulk on eBay. Usually last a couple of days
Lighthouse “Advanced” parts:
- JST-PH header (2 pin) (Mouser/digikey/etc.)
- 2xAA battery pack w/JST-PH connector (Adafruit, Mouser, etc.)
- 3D printed badge stand - this zip file has the most recent STL and FreeCAD design badge_stand.zip
Assembly (this is really the preferred order, otherwise you'll have to do some careful workholding to get it done):
- Safety Spiel (700 degrees hurts!)
- Basic procedure (add heat, add solder, remove solder, remove heat)
- Melt a tiny bit of solder on the square pad for the battery. This should be really thin (just to add a little better connection for the battery)
- Solder the battery clip on the back from the front (match the outline on the PCB) - this is a mechanical connection as well as an electrical one, so the holes should be well-filled.
- Note: They shouldn't push the clip down hard onto the PCB on the table surface. That revealed a failure mode (the pins can get bent in and won't hold the battery appropriately, or they may snap on battery insertion)
- Solder on the pin (push in through front, solder on back) - this is also a mechanical connection, so fill it decently.
- This tends to hold heat for a bit. I usually go into a spiel about LEDs being directional and how to find their negative/positive for a minute while it cools.
- Solder on the LED (short leg goes in the hole next to the flat of the LED on the silkscreen)
- Bending the legs keeps the LED from falling out and helps you see where to solder better.
- (I usually test that it works before clipping legs, but YMMV) - pop the battery in enough to get it to light.
- Clip the legs. Hold leg while cutting it so it doesn't fly off.
- Put in battery and finish.
If things go wrong:
- 90% of issues are just bad solder joints on the battery clip or LED. Reflowing joints helps.
- Battery won't go in? Probably too much solder on that first step. I usually bend out the battery clip with a small screwdriver until it accomodates the battery.
- Won't power? Did the LED get put in backwards? If so, put the battery in backwards and be done with it.
- Solder bridges on the LED pins can be taken care of by just dragging the tip of the iron through them.
- Rare problem: LED pad burns up?
- Once in a while somebody cuts off the pin. Desoldering it can be done (though a pain). Last time I just had them make a new one and used their pinless one as a “floor model”.
Future additions/modifications:
- Change design to use KiCAD instead of EAGLE.
- New badge shape? Try to keep it to less than 3 square inches (looking at the PCB as a 3 square inch rectangle containing your shape)
- Make battery pad not through-hole plated if humanly possible (prevents them soldering from the front?)
- Make the pads for the LED bigger (I've made a footprint in KiCAD for this)
- Probably additional silkscreen enhancements (add “PIN” where it goes?)