Step 6: Battery

Overview:
Battery technology comes in a lot of different varieties but the kinds that run your smartphones and ipods are the rechargeable lithium-ion variety. I'm no battery expert but for consumer-style electronics it seems this is the only way to go. Just be careful with the charging method because no one wants a flaming battery on their hands...

How to pick the battery?
Of course the Laser Ball could be driven with another style of battery but it's important to weigh out the characteristics and make a smart decision based on different trade-offs they offer. Let's think through the important factors in choosing a battery for the Laser Ball.
• It needs to fit in a tennis ball
• It needs to provide sufficient voltage (3.3V-5V) for the Teensy
• It needs sufficient capacity (amp-hours) to provide a reasonable battery life
• If needs to have a large enough discharge to provide sufficient current for the lasers and Teensy
• It needs to be rechargeable... trying to remove the battery pack from a fully-assembled laser ball is like trying to machete your way through a tropical jungle... bad joke, i know, but I think it paints the right picture.
Understanding the specs...:
I chose to use the 3.7V 850mAh Polymer Li-ion Battery from Sparkfun so lets see why...
• It will just barely fit in the tennis ball
• 3.7V gives me enough voltage for the lasers (3.2V) and the Teensy (3.3V)
• Its 850mAh capacity means a couple hours of battery life are possible if the Laser Ball draws ~300mA (850/300=2.8hr)
• It's max discharge rate is 2C which will provide enough current to run the Laser Ball. The C-value is just the capacity divided by an hour, so in this case a 2C rate is equivalent to 1700mA. The nominal discharge rate is 0.2C which is 170mA so the Laser Ball requirement (300mA) sits nicely within this range.
Get a charger:
Keep it simple and buy a basic Lithium-ion charger. There are lots available in the open-source community. They are simple circuits that can regulate the charging conditions for the lithium-ion batteries and provide a nice simple USB interface. Try this one from Sparkfun: LiPo Charger Basic

<p>im wondering if the lasers are damaging to the eyes</p>
<p>Very artistic!<br>Just a note from one of my Laser Engineer friends from the old days,<br>0.5 mW lasers are usually considered eye-safe. Going up to 5 mW is not recommended for direct exposure or repeated exposure.<br><br>The basic rule from long ago is:<br>0.5 mW = OK</p><p>&gt; mW not OK.</p>
<p>I would leave the lights on while poking them in so as to know immediately if a connection broke.</p>
<p>I built this inside a coconut because it offers far more room than a tennis ball. I used magnets to hold the bottom on. There is one small error in the two pictures you added. They have a laser hooked to pin 11, it should be pin 21 from the pins assigned in the program. I also added more patterns and a way to cycle through them all. The Teensy has plenty of memory to go wild with patterns. These instruction are very complete, mine worked the first time. I'm taking it to a party with a pirate theme. Thanks for a great Instructable.</p>
Genius
Total make it glow winner
<p>Hey guys...I'm new here...looking for a way to make a &quot;star shower&quot; laser blink!</p><p>Any hints?</p><p>Thanks guys!</p><p>P.S. Don't want to hijack thread if so please let me know how to start one. Thanks again </p>
<p>I want to make it completely sealed and to do so i need to be able to turn it off and back on with the IR remote, but ive never writen code before. Would you be able to help with this step? Ive got everything together and working (still waiting on the remote to show up). ive added an inline charger and 8 UV Leds i was able to write in to the code. im going to be using these as poi for a performance later this month. </p>
<p>Great instructable! I'm not able to watch the video in my country due to copyright grounds.</p>
I just found this project and have been working on it for a week now off and on. I am having an issue with getting the lasers to turn on. I have soldered everything to what I think is correct and I charged the battery. When I have the Teensy attached to the computer I get no errors when uploading the code but there is no blink or anything from the ball itself.<br><br>I double checked that the Teensy reset and that my Arduino software is set to Teensy 2.0. I have no idea as to why the lasers will not light at all. Please help.
That is strange as another user is reporting similar symptoms. Have you tried running the &quot;Blink&quot; example for the Teensy. If you can get that bit of code to work than that's a good sign everything is being uploaded correctly. When I first started working with the Teensy I had some initial trouble telling if the code was being uploaded correctly... using the &quot;Teensy loader&quot; and RST button can create some confusion.
This is the latest Laser Ball code I've developed. <br>http://dl.dropbox.com/u/43787305/LeoneLabs_Laser_Ball_source_v1_3.zip <br> <br>It corrects some minor errors in the other version and makes it a bit easier to make custom patterns. <br> <br>Good luck and let me know how it turns out.
<p>that link is broken, any chances of restoring it?</p>
<p>I guess I can't watch the video either.. it says &quot;This video contains content from SME, who has blocked it in your country on copyright grounds.&quot; Interesting...</p>
<p>It warmed my heart just seeing an honest to deity Mitutoyo pair of calipers! </p><p>Well done my man, well done! I think I'll make two for the wife...she's a sucker for such things.</p>
<p>Is a 5mW laser not dangerous for the eyes? Would work a 1mW also?</p><p>A Arduino Mini clone is cheaper as a teensy and not more bigger :)</p><p>But this Ball is very great!! thanks for that instructable!!!!</p>
<p>The AixiZ 5mW modules are eye safe, but if you buy them anywhere else, there is a chance they could actually be 35mW or more. See this discussion. <a href="http://laserpointerforums.com/f50/mini-red-diode-less-than-dollar-hits-31mw-88692.html" rel="nofollow">http://laserpointerforums.com/f50/mini-red-diode-l...</a> They can still cause eye damage, though if you stare into them long enough. Never look into lasers! Running them at 3V like this, they don't even put out 5mW.</p><p>No blue laser currently made is eye safe. That is not to be confused with BluRay, or 405nm lasers, which are actually near UV. None of those should really be considered eye safe because wavelengths that short can cause damage by other mechanisms.</p><p>Green lasers should never be considered eye safe unless they have been lab tested. The ones that are truly eye safe will be over \$75. I have heard of some Chinese pens being over 200mW fresh out of the box. Others are 0mW. Some can even be 500mW of very dangerous infrared that is nearly invisible.</p>
<p>Hmmmmm.</p><p>I wonder if Kim Jong-un can read it? :-)</p>
<p>Best Instructable I've ever read! So much fun and valuable information. Well laid out. Love all the details. Sorry for you Canadians - this is not to be missed. </p>
<p>I'm curious as to why did I get this 3 years old instructable this morning on my &quot;daily&quot; newsletter? And I live up north to the USofA (I'm in Canada) and the video isn't available for my country. Do I live too far? Never had to make this sort of commentary, but on a positive way: I do it with a smile, so for the &quot;be nice policy&quot; I am smiling and please, let's construct something that works. ;-) &lt;&lt;==-wink smiley</p>
<p>Just a nice response that I too cannot view the video... Good thing us Canadians are so nice!</p>
Popular projects often get recirculated if pertinent to an upcoming holiday or season.<br> I live South of the Nicest Nation, here in the USofA, an I too am blocked from viewing the video because of my country... maybe it's only good in Elbonia?
<p>It's not a regional thing. It apparently contains copyrighted content and was blocked on those grounds from all viewers. Disapointing.</p>
<p>What an awesome project!!! Thank you so much for all the time and effort <br>you put into documenting and sharing this project with the <br>Instructables community! This was my very first time trying out an <br>Instructable and also using a microcontroller, but your detailed <br>instructions got me through it!</p><p>The only problems I had were not putting Ken Shirriffs IR Remote Library <br>into the Arduino <br>Libraries folder <br>at first. Then the super cheap remote I picked up sent different <br>signals, but thanks to your code I was able to decipher them using <br>the serial monitor and then update them in the code (Then I also <br>noticed Ken includes this ability with his library examples). All works great!</p><p>Thanks again and what a great project!!!</p>
<p>Hi,</p><p>I have problems compiling the sketch:</p><p> IRremoteTools.cpp:5: error: 'TKD2' was not declared in this scope</p><p>Please, could you upload the .hex file of the project?</p><p>Thanks,</p>
Im having troubles uploading the code to the teensy. i get a notification when i try to upload that says &quot;'IRrecv' does not name a type&quot; and then the code IRrecv irrecv(RECV_PIN); is highlighted. i know next to nothing about codes for the teensy, and would greatly appreciate your help, as a really want to make this amazing project!<br>thanks!<br>
I had this same problem. You need to set the Arduino software to Teensy by going to &quot;Tools&quot; and then select the Teensy 2.0. That should fix your problem!
<p>Hi, I've problems compiling the sketch:</p><p> IRremoteTools.cpp:5: error: 'TKD2' was not declared in this scope</p><p>Please, could you update the .hex file?</p><p>Thanks,</p>
You may also be missing the IR remote library the code uses to read the IR signals. I see I didn't put a reference in the Instructable (but its commented in the code) but here it is... <a href="http://arcfn.com/files/IRremote.zip" rel="nofollow">Ken Shirriffs IR remote library</a>&nbsp;. It needs to be unpacked in the Arduino Libraries folder. Follow the <a href="http://www.arcfn.com/2009/08/multi-protocol-infrared-remote-library.html" rel="nofollow">tutorial </a>to get it up and running.&nbsp;<br> <br> I'll add this to the soon-to-be update...&nbsp;<br> <br> PS - thanks for helping wunder-bar
Thanks, i got it to upload now! but i just soldered all the wires on, and i have checked many times to make sure they are correct, but when i plug it into the battery, the lasers don't light up! please help, i'd hate all the money i put into this to go to waste!<br>
I think I'm having the same problem.... I need step by step instructions with the programming parts! There are so many things that can be missed or go wrong. I saw a note to change something for Arduino 1.0 on Ken's page, for example. I'm getting 2 errors when I try to upload the IRemote code. Something about a loop and main..... <br> <br>so, if the lasers don't light up is that mainly because the program is not on the Teensy? will they only light up at all if the programming is perfect? <br> <br>It's 2 things to upload to the teensy, right? Source Code and Remote codes??? <br> <br>I got the hex files to upload to the teensy to do fast or slow blink. Does that mean I did something right?? <br> <br>Please help. I'm making this for a friend who is using it in a high school play in less than 2 weeks! <br> <br>Thanks in advance, <br>Bill
if your still getting errors before uploading it it, you probably haven't changed the board under tools to teensy 2.0. also, be sure you have downloaded and unpacked the remote library from ken into the the library folder of the arduino software. this is wear i had to find and download an older version of the library, for some reason the new one wasn't compatable.
@expernoobz - Thanks for helping!<br><br>@osprey-npt - the programming can be tricky at first but I'm sure you'll get it with a bit of tinkering. If you've got the &quot;Blink&quot; program examples working then that's a good first step. As expertnoobz pointed out there may be some compatible issues with Ken's IR library and the latest version of the Arduino but it should be manageable. It might also be helpful to run through Ken's IR examples to make sure everything is connected up correctly. <br><br>Just for posterity, when you click &quot;upload&quot; all the tabs in the Arduino sketch are transferred to the Teensy, but the &quot;remote codes&quot; are there just for your programming reference in case you want to add some functionality.<br><br>Good luck!
Ah, yes. That was something that took me a bit of digging to do and totally forgot about. I believe you mentioned it in the IR part of the Instructable but not in the assembly.<br><br>I have some programming experience from collage and have always wanted to get into the hardware side of things. I never really found a project that really spiked my interest, but the Laser Ball sent it above and beyond! I'll help in any way I can. I love this Instructable and can't wait to post a pic of the final product!
<p>hola quisiera saver donde encuentro los materiales necesarios que se muestran en el video y tambien el costo</p><p>por fa</p>
This project is truly amazing, I'm just not too experienced with electronic diagrams. So I would be really grateful if someone could please post a really basic diagram or picture of where each thing is connected to. I'm using a JST connector instead of connecting it directly to the battery. Sorry for being a rookie. Thanks
Hi leonelabs love your instructable. I was just wondering how to ease the soldering of the grounding of the lasers I have been twidling with it for some time now and if you have some pictures on the soldering in some better quality or something I would really appreaciate it. / thanks you&acute;re awesome
This is one of the best instructables that I've seen. Really well done explanations about all aspects regarding what I personally hope for in a comprehensive instructable: scope, background, construction, and extended project ideas. Excellent!
Thanks! I appreciate the complement, it took quite a bit of work, I'm glad you liked it!
the way you have this set up is completely mobile. but i would like to know if its possible to skip the remote step, and add some sort of blue tooth or just some sort of a wireless component in order to be able to control the speed of the laser changes and patterns from a laptop.. if this is possible how would i go about doing so??
It's possible and certainly a nice idea. Off hand I couldn't tell you the best way to do it but I'm sure an Arduino bluetooth module exists out there. That would probably be a good place to start.
I am definitely making this project, already ordered the lasers. I have some questions though, the teensy 2.0 needs 5V to run, how does it work with only 3.7V from the battery? It doesn't look to have a regulator onboard. <br> <br>I was planning to try this with an Arduino Pro Mini because I've seen cheap knockoffs of these on ebay for \$6.20 delivered from HK, but I'm not sure they'd work from such a low voltage, they say they need 5V on the specsheet. Oh well, I guess I'll find out when I try!! <br> <br>If I ran the nano board from 5V and hooked up these 3.2V laser modules to the outputs, I'd think it would break them. <br> <br>Any ideas on this? <br>
What an awesome idea! Great work!
This is an amazing concept. What woul happen if I added more lasers?!?! Should I use a bigger battery? I was thinking about 15-20
great instructable, I couldn't imagine it more complete...
This looks awesome.
lasers can also bee bought from ebay http://www.ebay.com/itm/650nm-5mW-laser-module-3VDC-adj-lens-650-nm-8-X-13-mm-/380473849332?pt=LH_DefaultDomain_0&amp;hash=item58960235f4
Can you use 1mw lasers and still have it be effective?