SAFETY QUESTION: Going to be putting together a little wearables project for my daughter (who is almost 8 …going on 16 already - Dads of daughters you know what I am saying! …but I digress). Long story short the project includes RGB strips on a plastic headband (the “C” shaped type used to hold hair back from your face similar to this one - http://www.polyvore.com/cgi/img-thing?.out=jpg&size=l&tid=10209931 ).
I purchased a strip of the “skinny RGB neopixel strips” and ideally I would like to use them without the rubber weather casing to keep weight down and keep things lower profile. BUT it’s for my daughter to wear on her head, so needless to say SAFETY FIRST! So I will of course make sure the connections at the ends of the strips for power/signal are well protected, but I’m wondering about the intermittent solder points and such along the strips between the LEDs, etc coming into contact with stray hairs or her touching with her hand, and/or anything else.
Is this a valid concern or am I just being an over protective dad?
It should be fine. You are dealing with low voltage DC power which is really quite safe. If you want to alleviate your concerns you can just put a little hot glue on your solder points to insulate it.
Now if you were using something like EL wire which uses high voltage AC, it would be of major concern.
Oh yes you are - but it’s so good you ask.
So, health concerns start >60V (we’re running 5V that’s not even 10%)
Easy method for you, your wife, and your princess to find out: Take a 9V block (what is double what we use) and put it carefully !! at the most sensitive indicator: at the tip of your tounge. You’ll experience clearly a buzzing sensation. That’s it. Nobody will drop dead, no cell damage, no long term effect.
Put it on your skin and you’ll feel nothing. If anybody thinks he does: go for ballons.
OK. to the frequency: The fastest LEDs are driven with a PWM rate of 20kHz. This is just around the upper level of a human ear. SAFE !
Your LEDs have 400Hz. SAFE !
Now the best practice: Use clear shrink tubing to place the LEDs, securely on the head band.
Shrink half way down until you see the ‘teeth’ of the headband showing on the material. Take a cutter and >slightly< cut the tips, and when you shrink further you will see that the ‘teeth’ will penetrate through the tube. That will keep the ‘installation’ in place.
Use a small piece of plastic on the back to support (normally weak) solder joints at the beginning of the strip.
Seal still all open points with hot glue - and she even could go on a dive, but I know, you won’t let her
In a nutshell: 5V are safe. Frequency used safe as well. Extra enforcement only needed to prolong the fun.
Ah, I forgot - I also shrink tube the Teensys, just leave the USB accessable.
Post a video of your princess !
Agreed, the low voltages involved are quite safe. However, you should consider the battery. Lithium Ion batteries (usually 3.7V) can overheat or even catch fire if crushed or punctured. Overheating can also happen if the wires accidentally short together. Alkaline (1.5V not rechargable) AAA or AA size are generally the safest type if they’re badly abused.
Also, it should be said normal non-rechargable lithium coin cells aren’t dangerous. Only newer rechargeable lithium ion or lithium polymer ones are. Sadly, in these modern times the postal service and others only recognize the word “lithium” and treat them all as a fire hazard. But the older coin cell types like CR2032 are quite safe to use even if the battery will be abused.
There’s no need for safety reasons but, if it makes you feel better, you can dab nail polish on those connections. Clear, or the same color as the PCB.
If it’s going to be worn a lot, then protecting the strip is more of a concern. I’d mount the strip on the hair band, without the supplied casing, and then use clear shrink tube over both the band and strip.
And way to go for being the kind of Dad to make the effort!
You could also consider using some Sugru to smooth out and cover any solder joints. It also might be a fun (supervised) activity for your daughter to be involved with since it’s a little bit like play-doh & she can mix colors?
Thanks everyone for all the responses! The level of support within this group never ceases to amaze me! @Juergen_Bruegl - thanks for the suggestion of the clear heat shrink, seems perfectly obvious but hadn’t thought about that, great simple solution!
Got most of the bare bones setup last night on the breadboard. I’ll make sure to post pics, video, and code when it’s complete…but…In a nutshell the setup consists of: 3 different LED strips each on their own pin/array: 1 neopixel jewel (7 pixels) offset in the top/center of the headband, 1 neopixel skinny (144/m cut at 15 pixels on the left side, and 1 neopixel skinny (144/m cut at 28 pixels) on the right side. Being controlled via an ESP8266 Huzzah running a modified version of @Juergen_Bruegl 's ESP8266 Control code (https://plus.google.com/u/3/116700996827719272404/posts/3eEPjkVzAJ1) so she can control it from her phone. Code modifications include some UI tweaks (to “pink it up” for my daughter :D), some different animation sequences, and still need add some code to leverage some different pallets (in love with PaletteKnife BTW!).
At the moment/was planning on using CR2032 coin cell batteries to power the whole thing. I have one of these 2xCR2032 coin cell battery holders (https://www.adafruit.com/products/783). Although I’m not sure this power solution will be sufficient. The 144/m neopixels seemed like a great idea, but with 50 pixels (even with a max brightness of 25%-50%) and the huzzah…not sure I’m gonna have enough juice?
