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If you've been in a ski/snowboard shop lately you might have seen the K2 "ACS" system for their helmets, which integrates a headphone on one ear for stereo listening, and a headphone on the other ear with a boom mic for talking to your buddies over your walkie-talkies. You press on your earflap to talk and release to listen.

This looked like great fun and better than the usual hollering across the slopes and digging out our walkie-talkies when we lost each other. It also looked like too much money for 2 earflaps and a headset, when I had the materials at home to build it in half an hour.

Here, I make a busted Xbox headset and my ordinary K2 helmet into a K2 ACS helmet!

Step 1: Modify Headset to Fit Under Your Earflap

With the broken Xbox headset, this was easy as it was already broken off of the part that holds it on your head. I just cut off the broken part and filed it smooth.

Remember, you want this to be comfortable. You are wearing it all day to ride!

Step 2: Reverse Earpiece and Microphone Connections, Add Talk Switch Connection

Most walkie-talkies use the opposite "polarity" on their connector to other headsets. So converting any phone/xbox/cell headset to walkie-talkies, usually requires popping it open and swapping the mic and headset wires.

Test it first! You may not have to swap the wires if you have weird walkie-talkies or a funky headset.

Use an ohmmeter to find the mic, earphone, and common wires. Leave the common wire alone.

Pics show before and after. Note the white and red wires have been swapped.

OOPS, I FORGOT A PIC!
The simple swap is enough for voice-activated use, but on the mountain, the wind noise is too strong, and you need to use push-to-talk.

The pic I forgot to show... was of me adding the wires for the push-to-talk switch.

You want to put a hole in the headset (there's already one there on the xbox headset) and feed in 2 wires for the switch. Remember to tie a knot for strain relief, or they could rip right out and destroy all your work.

Now, don't connect the microphone to the pad where you were going to swap it to. Instead, connect it to one of the wires going out of the headset. Connect the other wire to the pad. You have put the switch wires in series with the microphone.

Step 3: Two-cent Poor Man's Switch.

I know I'll get booos for this one. But I used the 2-penny switch for a reason, and not just because it only costs 2 cents.

It's hard to find a switch as thin and with as little action as the 2-penny switch, which is perfect to slip between the headset and the earflap. It has a very large area which responds to a very small force, meaning you can slap at your earflap with your glove and it will come on. It also means there are no external parts to get snow in or look ugly.

If you find a thin switch that you can activate with gloves on then by all means, use that instead. Or mount another switch on the outside if you find a nice looking one.

Anyways, image 1 shows preheating the penny. It's damn hard to solder to a penny, so use a big iron and try to balance the penny somewhere it won't conduct all the heat away. Once solder starts to stick to the penny, you can solder the wire to it. Do this twice, once for each side.

Now it should look like image 2. Let it cool, and then build a thin spacer on half of one of the pennies with tape. Can you see the tape in the pic? Build it thick enough that it will not touch unless you were to press on it.

Then wrap the whole thing up in tape like image 3. Note the gap between the pennies. Test it well with your walkie-talkie. Most important - it must not get stuck on! It should require a light press, but not too light.

Step 4: Putting It All Together

Cut a small hole in your earflap and push the microphone through so it will go in front of your face. It should be a very tight fit.

Position the switch with tape or something and give it some tests with your walkie-talkie. It should switch to transmit easily and reliably when pushing your earflap with a glove on, but not come on when you tilt your head. You may have to adjust your penny switch spacer, too.

When you find a good spot, fix it there with your favorite adhesive. Don't use one too strong, in case you find that nice switch you were thinking of to replace the pennies.

Step 5: Push to Talk. Act Like a Jerk From Farther Away Than Usual!

"Do you require assistance?"
I know it's been a while since there was a comment, but I have a few questions. My friends and I play airsoft. I thought'd it'd be pretty neat if we bump-up the realism in the game with helmet (in my case a mask) to helmet communication. Now for the questions:<br> <br> 1. I may not be getting this, but how do you sync up the walkie talkie and the Xbox Live headset? I skimmed over your instructions, but have yet to try it.<br> <br> 2. Is it possible to have helmet-to-helmet communication? As in 1 Xbox headset to another Xbox headset, not to a radio. I would really only want just two headsets (for now, at least). I'm not really expecting this part to be possible with this current set-up, but any information you can give will be extremely helpful.<br> <br> I'm currently majoring in Electronic Engineering Technology, so I have a slight idea of what I'm doing. I thought that this would not only be quite helpful and efficient, but also great practice for the field I'm going into.<br> <br> Thank you for your time,<br> Darryn
might have to try this, i work as a ski patroller and its always hard to hear my radio
Anybody have a link or schematic for the actual K2 headset ("Baseline ACS")? Trying to make it work with a yaesu vx-170 (2m radio) and its being a bear. Thanks, Joe
the most common problem with these things is which part of the plug is headphone/mic. The ACS will be set up as a "FRS walkie talkie headset" - try a cheap cell phone headset or xbox headset, and see if the transmitter comes on. They are wired up the opposite way. The only thing on the schematic would be a switch between the mic and the plug to do the push to talk. Ring them out with the output from a stereo, tapping it to different parts of the plug - you won't hurt the mic, and it's disconnected by the switch anyways. Then find out which is which on the radio, and either make an inline adapter or modify one or the other. Never seen the vx-170, but there is always a chance it may use a different ptt system than the normal one (which turns on the transmitter when the mic is connected).
Thanks. I played with it some this weekend and think I've got a handle on it. I had made some wrong assumptions that was making it a lot harder than it really was. If I get the right adapter coming out of the Yasue I think its going to just be plug and play. (And will still be able to use the MP3!) Another good example of why you shouldn't let a mechanical guy get too close to a soldering iron. Joe
Tell me more about success with the Yaesu VX 170. I have the same radio and the ACS and the headset/mic 4 wire plug for the radio but need the schematic for the headset end.
Alright, I just bought two K2 ACS' and a set of Cobra MicroTalk (PR-700 WXC) FRS/GRMS twoway radios that come with ear phones and mics. The walkie talkies have a button on the mic that came with them that you need to hold down for it to transmit. However when I plug my helmet in I can recieve a message but no matter what combination of buttons on my helmet and holding the talk button, I can not transmit. From reading your comment hear, I'm assuming the two conductors on the plugs are inverted. Do you agree? If so, can I just buy a cross over plug (I don't really want to go with the home made version). I don't have another headset available. Any suggestions would be greatly appreciated. Heading up the mounting on Friday. Thanks!
I got the same problem with my ACS...just wondering if you ever got them to work with your radios
Yes I did get it to work, all I had to do was not plug the helmet jack into the walkie all the way, I left it out about 2mm (put in a couple washers) and it works fine. Random eh?
Yeah, but I had to go into the earphone and disable the PTT (push to talk) switch by shorting across one of the traces in the PCB (then glued the earphone back together). Did finally work though (using a wrist-mount PTT).
what is the signal strength of this?<br /> <br />
could you use a ps3 or was or 2&nbsp; eneyway headset
you could mount the switch with bolts.
Here's a "random" thought I was thinking about. What if instead of going around getting pennies and sawdering them to some wires, couldn't you possibly get some switches, like a on/off switch and make it so you can make it work the same? (and just in case someone else said this and I missed it sorry, but it is a little late for me)
As mentioned in the instructable, most switches don't hold up in the environment of extreme cold and moisture. I have tried to swap in several push-button switches over the years since I wrote this and all failed (cracked plastic, dead spring, corroded contacts) - the 2-penny switch still works, so I guess it was a good call! A proper industrial button (think emergency stop button) would work great but would look stupid on the helmet. This one is invisible inside the earpiece.
Or even a button... those wired buttin things you see on some older models of Vaccum cleaners... just in case u needed a visual
is ti possible to use a ps/2 headset to do this with
An enhancement recommendation: I built a similar set up using a throat mic. No wind noise, no snow in the mouth piece after a powder day wipe out. Totally hidden under a neck warmer. And pretty cheap:<br/><br/><a rel="nofollow" href="http://www.firefoxtechnologies.zoovy.com/">http://www.firefoxtechnologies.zoovy.com/</a><br/><br/>Great article, thanks!<br/>
That site shows the price of $55. Not too expensive indeed. But it would be more fun to MAKE your own! I've experimented with one that I made and it works with one bug. It REALLY picks up bass in your voice! Nothing that can't be equalized out.
where do we get the power supply for the ski helmet???? will u please tell me which wire is swapped wtih the 2 penny???? does it require 2 helmets to be albe to communicate???? if it yes it means i should make 2 ski helmets????
The power supply is in the radios. This is a passive headset. The wire connected to the pennies is the one connected to the microphone. You don't need 2 helmets, but you do need 2 radios! And your buddy holding the radio while he skis will be jealous of your helmet! Update on this project! I've been trying to find a better switch that can be mounted to the helmet shell this ski season, so it's easier to use. However... it seems very hard to mount things to a ski helmet shell in the cold. Any adhesives I've tried just crack off when I push the button, when it's too cold! My latest system with a microswitch worked much better than the penny switch for about half a day, until pressing it with a glove snapped it off the helmet (again!). So far, the penny switch has been the only one to be reliable enough to last longer than a day, what a shame. And now the season is almost over again, wow, can't believe I posted this so long ago! It's hard to perfect something with such a sporadic development cycle (aka the night before a day I go skiing)
Some radios have a feature (labeled VOX on mine), that allow them to turn on automatically when you start speaking, eliminating the need for a transmission switch. At the correct squelch level they should turn on automatically while receiving too. Alternatively, you could add this function with N2222 transistors. Just use voltage from the mic line to make them switch the radio Tx on when you speak... you'll need to consider the input resistance of course. I have an old mic and some N2222's lying around. Send me mail through instructables if you need me to do a little work. Fun fact: N2222's can also be used to create touch switches at 9v.
My radios actually have vox! The trouble is, when i'm skiing at any speed, wind noise will turn the vox on. And if I set the vox high enough to not get hit by the wind, I have to yell to activate it, and then the wind keeps it on afterwards anyways. Wind is surprisingly loud. I thought vox would be good, but any time I've used it (skiing, motorcycling, construction, testing long range things) - I found it really sucked, cutting off tons of words on the start and then staying on too long after i was done talking. Or perhaps the vox just sucks on mine (cobra microtalk FRS radios)
Hm, not being a snowboarder, I hadn't thought of that! Only thing I can think of is covering one end of the mic to shield it from wind. You could also put it along your throat, see if it picks up less noise. I have some of those radios mall security guards use... they have an earpiece which is both a mic/speaker. Your jawbone conducts sound to it. The vox on that thing is quite effective, that could be a cool system!
Yeah, I'd love to have a throat mic or bone conduction mic, that would obsolete this system pretty fast! Last I saw them, they were worth quite a few bucks, though. How much did you have to spend on yours? Might pick up a pair to give them a try, if they've come down enough.
Ah, I didn't buy them OEM... they came attached to some used radios I bought cheaply. If you happen to live in Montreal, consider them yours.
cool!!
cool, would running the switch to your wrist be too awkward?
I thought of that first, but realized that K2 put it on their helmet for a reason - I don't want a wire running from my head, up and down my arm, to my radio, tangling up my arm while I ride and making it a pain to put on my jacket. This way you just throw on your lid, plug it in and are good to go.
why dont you mount the radio on the helmet??
1)mounting it outside would make it look like a homebrew ordeal which doesn't do too well for when you're trying to impress the ski bunnies... 2) mounting it on the inside would probably involve modding safety equipment... which isn't a good idea either.
Brilliant!!
Wow, I don't know how I missed this post. This is awesome! Great jorb, yo!
So I took it snowboarding yesterday - it worked great but had a small problem with the switch - even though it was easy to push, pushing it jammed the earphone into my ear and made it a bit sore after a day of talking. Will be moving the switch to the hard part of the helmet and most likely replacing it with a "proper" switch since it won't have to be quite so easy to push. Why not put the radio on the helmet? Hahah. These are FRS walkie-talkie radios... that would look pretty dumb and result in smashing my radio if I fell. Also, I use them on my motorcycle, so gluing one to my helmet... not a great plan. Gutting one and hiding the guts in the helmet - that would be cool, but way too much work, and there is no empty space in the helmet shell to put it.
very nice
LOL,I broke my headset in the exact same area!!! Cool Idea, I want one.
Awesome! BMW makes a bluetooth motorcycle helmet which is sold for a ridiculous amount of money. At some point I want to figure out how to retrofit a traditional helmet.
That is amazing. I wish i thought of that. Only thing, would it be too hard to add a spring or something inbetween the pennies so it wont be set off by accident.
The tape spacer acts a bit springy, pushing the pennies back apart when you let go. The gap between the pennies is too small to fit a real spring in, only something springy - It's intentionally very sensitive so it can be set off by pressing gently against the outside of the earflap. It may act up with time - I will find out.
Very cool. Well documented and the finished product looks very clean.

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