BogerTech Model Rocket Launch Controller Plans

Step One: Read the Disclaimer.

Disclaimer Any use of these plans is at your own risk! These plans are presented as is. No warranty is expressed or implied. I cannot assume any responsibility whatsoever for any damage or injury resulting from the use or misuse of these plans either during the construction of the product or use of the resulting product .  It is your responsibility to determine the safety and suitability of anything you construct using these plans. Model Rocketry is a dangerous hobby if safety regulations are not followed.  The NAR safety code should be followed for all launches.  For added safety I strongly recommend that the launch cable be connected to the rocket first and then to the controller only when the launch area is cleared.  If the controller should develop a short and cause a misfire everyone will then be at a safe distance.   There is no such company as BogerTech and I conduct no business under that name.  It is a fantasy name I use in connection with my hobbies.  I am a minister and not an electronics expert.  I make no claims otherwise.  Adult supervision is recommended for the making  and use of this controller.

Step two: Decide which version of the Launch Controller you wish to build.

Version 1: The Key-switch version. This is the most expensive version.  The key-switch ran me  $4.99 plus shipping and tax from Radio Shack.  (It is not available in their stores.) The main advantage of the Key-switch version is that an actual key must be inserted and turned before the controller is armed.  This can be a big safety advantage (especially if a lot of curious young kids are around. But only if an adult maintains control of the key.) The biggest disadvantage is battery drain if the key switch is not turned off following a launch.

Version 2: The more economical version is the Push-button version.  The red push button I purchased from Radio Shack and used as the launch button comes with a black push button which can be used to arm the controller in place of the key-switch.  When this version is used it is imperative not to hook-up the wires to the controller until after they have been connect to the rocket.  If someone should accidentally step on the controller or otherwise press both buttons the rocket will launch immediately.  It has the advantage that the launch becomes disarmed saving battery power as soon as the armed button is released.

Version Comparison Table

Step three: Plan your project. Now that you have decided which version of the controller you wish to build.   Read the rest of these plans and make sure you understand them.  Review the parts list. make sure you understand how each part is to be used.  Take inventory of parts you may have on hand that are suitable for the project.  Then order or purchase the other parts you will need.  The Launch button must be a momentary switch that is normally open (off).  The lamp used must have enough load to keep the igniter from burning.  I used the same bulb as that used in some commercial  model rocket launchers. the resistance of this bulb is only three ohms if my meter was working properly so a lot a resistance isn't needed.  You may wish to test your bulb/resistor combination before proceeding with construction.  

Also download  and print the templates for cutting the holes in the box. The templates are scaled 300 pixels to an inch.

Step four: Make the launch cable.  For this step you will need two small alligator clips and hookup wire, either zip wire or twisted pair will do.

Depending on the size engines you will be launching, cut the wires: 17+ feet (for D and smaller engins) or 32+ feet (for larger engins). Strip as much insulation as is needed for your clips from both wires at one end of the cable and solder an alligator clip to each wire.  Depending on the thickness of your wire strip a half inch for thicker wire or an inch for thin wire from the remaining to wire ends.  This end will connect to the terminals on the controller.  With the thin wire ,such as that found on the parts page, bend the stripped end in half so that it is doubled over.  Coat it with a thin layer of solder.  This will make it easier to attach to the terminals.  You have now completed the launch cable.

Step five: Drilling holes.  For this step you will need the templates and the project enclosure.  

Cut out and tape the top template to the metal top of the project enclosure (Use the plastic top if you prefer, it is probably easier to cut.)  Do the same with the side template along whichever of the two long sides of the enclosure you decide will be the back.  If you have substituted any parts you will need to change the size of the holes to match the parts you are using. You will notice that there are two circles one inside the other labeled key. By now you should have decided if you are going to build the key-switch version or the push-button version.  The outer circle is the 3/4 inch hole needed for the key switch, the inner circle is the 1/2 inch hole needed for the push-button.  The circle labeled Launch Ready is for 21/32 in hole needed by the lamp assembly.  The launch button requires another 1/2 inch hole.  Drill, cut, saw holes where indicated.  I used a metal cutting tool on a Dremel Rotary tool. (It skated quite a bit, scratched up the top and the key hole ended up not exactly in line.  I hope you have better luck.) Drill two small holes, 3/32 I think is the right size.  Use a bit large enough that the posts on the back of the binding posts will pass through the box but the nuts that hold the binding posts in place will not.

Step six: Mount the top components. For this step you will need the project enclosure top piece, the key switch, the lamp assembly (with bulb), and the launcj button.

Now you can go ahead and mount the components to the top.  Use the picture on the home page if you are not sure where everything goes.  All components mount the same way:  remove the retaining nut and washer. push the component through it's proper hole, replace the washer and tighten in place with the nut.  The launch button and lamp assembly will be easiest to wire if their terminals line up parallel to each other. (It may be easier to put the bulb in the lamp assembly berore it is mounted in place.) The key switch has a water proof cover.  I decided the project looked better without it.  You may use it if you wish.  I chose to mount it so that the key slot was perpendicular to the front and back of the box when the switch is off.

Step seven: Mounting the terminals (binding posts).  For this step you will need the project enclosure bottom and the two binding posts. Because polarity is not an issue I chose to use two red ones.  You can use any colors you wish in any combination.

Remove the hardware from the binding posts.  Make sure the terminal lugs (red part) un screws easily. You may have to grab the mounting screw part of the post with pliers as you loosen the red terminal lug.  Mount each post to the back of the enclosure by placing an insulating black washer on the mounting screw, passing it through the hole in the enclosure and adding a second washer and then the nut.  Screw out the red terminal cap until you can see the hole bored through the terminal.  Line the hole up so that if looking from above the enclosure you can see straight through the hole.  Tighten the nut.  Place the second nut and the wiring lug aside for now.  Repeat this step with the remaining post.

Step eight: Mounting the battery compartment.  For this step you will need the battery holder, one of the wiring lugs & one nut from the previous step, the project enclosure bottom, and some double stick foam tape.

Solder the black wire from the battery holder to the terminal lug.  Cut two strips of double stick foam mounting tape the length to the battery holder and us them to fasten the battery holder to the enclosure as follows.  with the binding posts away from you place the battery holder on the left side of the bottom of the enclosure with its leads coming out towards the right. You will need to position it slightly to the right of left side screw posts so that it will sit flat on the bottom. See photo 1 below. (Batteries should not be in place untile all the wiring is completed.) Slide the black wire terminal lug assembly over the left binding post mounting screw and secure with a nut.

Figure 1

Step nine: Wiring it up. Are you still with me? Have you given up yet?  Have you thrown the whole  project in the trash yet?  Good we're going to make it.

For this step you will need the remaining wiring lug and nut of the binding posts, and some hook-up wire (you can use the wire left over from making the launch cable) and the project enclosure. Refer to Figure 1 above and Figure 2 below  for the next steps.

Cut a piece of hook up wire approximately six inches long.  Solder the remaining lug to one end connect the other end to one terminal of the  Key Switch (or black push-button depending on your version).  

Cut a wire long enough to reach from the key-switch to the lamp assembly.  Connect this wire from the other terminal of the Key Switch (black push-button) to one terminal of the lamp assembly. Do not solder it to the lamp assembly yet!

Cut two wires long enough to reach from the lamp assembly to the launch button. One wire should be soldered together with the wire already connected to the lamp to the lamp terminal. this wire is then soldered to one terminal of the launch button.  The second wire is soldered to the other terminal of the lamp assembly and leads to the other terminal of the launch button. Do not solder it to the launch button yet!

Get the bottom of the enclosure and solder the red battery holder lead together with the second wire from the lamp assembly to the second terminal of the launch button. Make sure that the terminal of the launch button with the battery lead attached does not connect directly to the terminal of the lamp assembley that is connected to the key switch.  One terminal of the lamp assembly should have two connections, one to the key switch by itself and one to the launch button by itself.  The other terminal of the lamp assembly should connect only to the terminal of the launch button that is also connected to the battery lead.

Now attach the wiring lug that is on the lead running from the key switch to the remaining binding post with the remaining nut and tighten securely.

Figure 2

Step ten: Initial test.  For this step you will need 4 AA batteries, the project enclosure and your launch cable.  

Put the four AA batteries in the holder.  Put the cover in place but do not screw down yet.

Turn on the key switch.  Nothing should happen.  If the lamp burns you have a short between your binding posts. Correct the problem. Turn the key off.

Connect your launch cable to the binding posts by unscrewing the red caps enough to reveal the holes in the posts.  Pass the bare end of the wires through the holes and tighten the caps back down. Connect the two alligator clips on the other end together. Turn on the key switch. (or press and hold the black button.) The launch ready light should burn.  If not recheck your wiring and check for loose connections or potential shorts. If you substituted a LED for the lamp make sure it is connected the right way. If the lamp still does not work check for a faulty component.  

With the lamp burning press the red launch button; the lamp should go out as long as the button is pushed.  If so go to step eleven.  If not you probably have a faulty fire button.

Step eleven: Final Assembly. For this step you will need the project enclosuer and the four screws that came with it.

Congratulations, it appears your unit is working properly.  If you have the key-switch version remember to turn off the lamp. Screw the cover in place.  

Step twelve: Label your completed Launch Controller.  Now make some labels for your controller using your printer or other labeler. You will need: "Launch Ready" for the light, "Launch" for the launch button, and "Arm" for the push-button version, or "Off" and "Armed" for the key switch version.  See the picture on the home page for ideas of sticker placement. Your launch controller is now ready for use.

Remember for added safety always connect the launch cable to the rocket first and then to the launch controller.

I loved to hear from you about problems, improvements, construction tips, etc. theBogue@earthlink.net.

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