Introduction: Cell Phone Controlled Remote Airsoft Grenade Detonator

About: A mechanical engineering graduate from JBU, I enjoy putting motors on things that don't already have them, tinkering with small gas engines, airsoft, paintball, and pyrotechnics. I am no longer active on this …

So even though it's January, I went camping this past weekend. When I came back from camping, Lo and behold I saw on my desk a cell phone! This gave me the ability to realize a dream I have had since I was in high school: To build a remote detonator to use with my Thunder B airsoft grenade. For those of you who have subscribed to me since I first became an active member of Instructables will know that a) most of the airsoft stuff I make has either exploded, or been really super sketchy, and b) I have not submitted an airsoft related instructable in quite some time! This instructable will solve both of those problems. First off, I have come a long way since my backyard, blow 'em up style of game play. I have attended several indoor games and milsim ops, both of which do not allow the use of explosives. However, most of these places will allow you to use certain kinds of "grenades" such as the Thunder B airsoft grenade. Note that this grenade does not actually cause a bb strike, but most places will play with "radius rules" in order to contain the realism and allow the use of grenades. What this device does, in a nutshell, is cause the pin to be pulled on the grenade, causing it to explode. This entire project can be done for under $20, assuming you already have a few parts lying around. This does not include the monthly charge of the tracphone, but considering the cost of some commercially made airsoft equipment out there, that is relatively cheap. Also, you will have the ability to detonate this anywhere that you have cellphone service, something you cant get with any other available device!

Step 1: Obtain Materials

The materials for this project are very few and readily available at Radio Shack or Wall-Mart.


  • Soldering iron
  • Hot glue gun
  • Pocket knife
  • Dremel (option, I didn't use one)
  • Saw

  • Trac phone (~$10 at wal mart)
  • electric motor (must be powerful enough to pull the pin, I already had one)
  • 1 or more 9 volt batteries
  • 2 AAA batteries and 5 volt relay
  •                                 OR
  • 3 V relay (will discuss this later)
  • Assorted small wires
  • Solder
  • Hot glue
  • Wood blocks (or some other buffer, discussed later)
  • String
  • Paperclip
  • 9 volt battery clips

Step 2: "Fix" the Cell Phone

Obviously the most fun part of the project, modifying the cell phone! what you want is to basically extend the leads to the vibrator motor of the phone. To do this, simply take apart the phone and find where the vibrator contacts are. Then all that's left to do is splice/solder in some wires and cut a hole in the back of the case to run your wires through. After you re-assemble it, your done with the modification! bet you didn't know it was that easy huh?

Step 3: Wire the Relay Circuit

This step will depend on which relay you chose. Since the cell phone vibrator modification will give you a 3v output, A 3 volt relay sounds like it would do the trick. However, all I had was a 5v relay. Bummer. However there was a simple solution to this problem. Just simply add another 3v source in series with vibrator output, and bam! 6 volts when the phone vibrates, which will trip the relay. Now on the other side of the relay you will have your motor supply source. I used 18 volts, but you will want to get as close to the nominal voltage for your motor as possible. I would recommend that you do testing to see how much voltage your motor needs to be able to pull the pin on the Thunder B grenade.

Step 4: Stick Everything Together

Now you don't want all of these wires sticking out all over the place do you? No way! Now it's time to stick everything in a nice, neat package. In the future, I will be using a project box to protect the phone and electronics from stray bb's and such, but for the first prototype This worked just fine. Make sure that there is someting seperating the motor and thunder B so that there is space for the pin to be pulled. This step will largely depend your personal build, so I will provide pictures as guidance but by no means is the set way to do things.

Step 5: Adding the Thunder B and Finishing Touches

For this first prototype, I just wrapped electrical tape around the grenade to hold it in place and that has been good enough. In the future though, there will be some method of more securely holding the grenade attached. To finish, I wrapped some camo duct tape (don't hate) around the whole thing. this really helps keep it camouflaged when I hide it next to a tree or something. 

Also, here's a little hint. disconnect the motor supply source before turning on the phone. It likes to vibrate when it turns on, so, you know, if you would happen to have everything set and THEN turn on the phone.... It wont be pretty. And that is just speaking from experience.