Tour of my DIY Launch Controller

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Kevin TMR

Member
Finally something good came from quarantine. Built my dream launch controller and just published the video about it!!

Time to keep dreaming and figure out what to make next, what improvements would you make to it??

Joshua F Thomas

Well-Known Member
High quality video! I'm quite impressed.

I absolutely agree with you on the "because it's awesome!" reason to build a launch controller. I get the exact same feeling out of building my own 12V controller with key-lock and big heavy-duty switches. It really brings you to that "I'm a rocket scientist!" feeling.

Your build quality is quite high! It looks very professional. I went through all of the same "how do you build a launch controller with delivering power and continuity" as you go over. A few thoughts:

What's the power delivery and voltage? Is this a 12V launcher? Are you using a lead-acid battery, or lithium, or what?

One thing I *don't* notice is a safety interlock. So long as the power is enabled for continuity check, any errant button push will launch your rocket! This is not good if you're trying to debug a continuity problem and you accidentally smack the launch button! Rocket will go off in your face. In my launch controller I have a safety key that must be turned before it is possible to launch. I can safely play around with getting my continuity working if they key is removed; it's impossible for a launch to accidentally happen.

Kevin TMR

Member
Hey Josh, wow thank you!! That means a ton.

The goal of our channel is to inspire newbies to the hobby to get started & keep going, or inspire the veterans to have more fun & fall back in love with it. So it's a 6v launcher for LPR's. But the next build will 100% be for a 12v system.

I've never thought of a safety interlock, but I totally see the benefit of it you can never be too safe! Any chance you have pics or a video of your build?!

Joshua F Thomas

Well-Known Member
Absolutely, enthusiasm is important.

The link in my last post goes to the thread where I have some pictures, along with my wiring diagram. I don't currently have an video, but I really should do that the next time I launch. Other people have been asking for the brightness of the LED in full sunlight, so I'll have to make that a priority.

Kevin TMR

Member
YES that's awesome!! I don't know how I missed the thread.

And dude seeing other people building their own based upon yours, that's super cool!

rklapp

TRF Supporter
All yours for the incredible price of $19... Kevin TMR Member All yours for the incredible price of$19...

Chasing a dream of doing model rockets part time!

rklapp

NAR# 109557
TRF Supporter
I like the content on the website.

I'm thinking about it. I'm interested in the continuity wiring.

Kevin TMR

Member
I like the content on the website.

I'm thinking about it. I'm interested in the continuity wiring.
Thank you!! It's been a lot of fun to create and we've learned a ton from it. I'm really proud of the course, but as long as you're building your own launch controller you can't go wrong either way!

rklapp

NAR# 109557
TRF Supporter
Here's my current controller. I had to use a bigger wire because the speaker wires didn't have enough current.

BBowmaster

Well-Known Member
Grrr. I need a better launch controller and now you guys make me want to build my own.

Edit: Screw it. Bought the course. I’m taking the plunge!

Last edited:

Joshua F Thomas

Well-Known Member
Here's my current controller. I had to use a bigger wire because the speaker wires didn't have enough current.
What gauge were the speaker wire?

The really good solution, by the by, is to make a box local to the rocket pad that has shorter wires and the batteries, plus long wires to a firing controller that just switches that power onto the igniters. Less wire will mean lower current losses.

rklapp

NAR# 109557
TRF Supporter
Typical speaker wires. I subsequently sacrificed an extension cord and now the igniters burn bright.

PXR5

Starship Hijacker
TRF Supporter
Very nice Kevin!!!!
Awesome video!!!!

Joshua F Thomas

Well-Known Member
I don't know what typical speaker wire is for you, but when I had a nicer home stereo system it was 12 AWG which is pretty beefy. 30 feet of that will only drop about 0.2 volts on 2 amps. Use https://www.calculator.net/voltage-drop-calculator.html to see what kind of voltage drop you get.

My launch controller uses 14 AWG for most connections.

jrap330

Retired Engineer, NAR # 76940
TRF Supporter
Finally something good came from quarantine. Built my dream launch controller and just published the video about it!!

Time to keep dreaming and figure out what to make next, what improvements would you make to it??

Finally something good came from quarantine. Built my dream launch controller and just published the video about it!!

Time to keep dreaming and figure out what to make next, what improvements would you make to it??

One thing about this video..it shows how poor the "new" starters are...thank you Haz Mat. And I had the same realization about the continuity check a few years ago....it is NOT a simple complete the circuit and send amps to igniter..it is complete the circuit to light the buib/led and then short out buib/led so all current goes to igniter and ignites engine. As an Electrical Eng (E.E) I never bother to figure that how....so even E.E's mind was blown

Joshua F Thomas

Well-Known Member
Yeah the Estes stock igniters are not great. I use QuickDip now to give them some actual pyrogen.

And I had the same realization about the continuity check a few years ago....it is NOT a simple complete the circuit and send amps to igniter..it is complete the circuit to light the buib/led and then short out buib/led so all current goes to igniter and ignites engine. As an Electrical Eng (E.E) I never bother to figure that how....so even E.E's mind was blown
I dunno, isn't that just like, parallel wiring with a controlled switch? It's not all that complicated.

Continuity check: Use a resistor and LED, current is limited because of the resistor
Actual firing: Switch or relay creates low-resistance path directly to the igniter

If you're using an on/off or momentary switch for the continuity check, then you're even bypassing it entirely. This is how mine works. There's no magic here, just two current paths, and the continuity check draws < 100mA (I hope yours does!) because of the resistor used for the LED.

Kevin TMR

Member
Here's my current controller. I had to use a bigger wire because the speaker wires didn't have enough current.

View attachment 426324
I love all the decals & electrical signage. Plus we use a similar auto toggle like you have in the middle. I love the way it feels!

Kevin TMR

Member
Grrr. I need a better launch controller and now you guys make me want to build my own.

Edit: Screw it. Bought the course. I’m taking the plunge!
YESSSSSSS DUDE welcome aboard!!!! Team homemade launch controller for the win!

gtche98

Gary W
Yeah the Estes stock igniters are not great. I use QuickDip now to give them some actual pyrogen.

I dunno, isn't that just like, parallel wiring with a controlled switch? It's not all that complicated.

Continuity check: Use a resistor and LED, current is limited because of the resistor
Actual firing: Switch or relay creates low-resistance path directly to the igniter

If you're using an on/off or momentary switch for the continuity check, then you're even bypassing it entirely. This is how mine works. There's no magic here, just two current paths, and the continuity check draws < 100mA (I hope yours does!) because of the resistor used for the LED.
I think the part that blew my mind was not the complexity, but the simplicity. And the fact that for the Estes controller, the bulb is the resistor, making it even more simple. When you think of the design specs (launch a rocket, provide continuity check, safety interlock), an Estes controller is pretty brilliant.

Kevin - Your step up from the Estes controller is quite beautiful. I love the simplicity of the black CF box with the ruggedness of the switches and launch button. Looks like it would be at home between the two control screens inside Crew Dragon.

jrap330

Retired Engineer, NAR # 76940
TRF Supporter
Yeah the Estes stock igniters are not great. I use QuickDip now to give them some actual pyrogen.

I dunno, isn't that just like, parallel wiring with a controlled switch? It's not all that complicated.

Continuity check: Use a resistor and LED, current is limited because of the resistor
Actual firing: Switch or relay creates low-resistance path directly to the igniter

If you're using an on/off or momentary switch for the continuity check, then you're even bypassing it entirely. This is how mine works. There's no magic here, just two current paths, and the continuity check draws < 100mA (I hope yours does!) because of the resistor used for the LED.
I did not mean complicated,.. I men usually I think a switch completes a circuit and it never occurred to me,until someone wrote an article about building your own..that you are not completing a circuit when you hit launch...but you are shorting out a current limiting bulb or LED so all juice goes to igniter. Usually shorting out anything is not something that was review/talk about in school during my course of study. So it blew my mind also.

TRF Supporter

Glasspack

Nice work Kevin...…….

I built my own 4 pad high Power controller as well. Such a great deal of satisfaction building and using your own controller !!

Kevin TMR

Member
Nice work Kevin...…….

I built my own 4 pad high Power controller as well. Such a great deal of satisfaction building and using your own controller !!View attachment 426417View attachment 426418
That's awesome!! You kept the layout so clean & organized this is brilliant. A multipad is hopefully on the to-do-list for this winter!

jrap330

Retired Engineer, NAR # 76940
TRF Supporter
Finally something good came from quarantine. Built my dream launch controller and just published the video about it!!

Time to keep dreaming and figure out what to make next, what improvements would you make to it??

Since you mention 2 buttons for 2 kids.... a number of designs used 2 buttons instead of safety key...buttons space far apart. I believe a commercial launch controller uses this approach.

Joshua F Thomas

Well-Known Member
Since you mention 2 buttons for 2 kids.... a number of designs used 2 buttons instead of safety key...buttons space far apart. I believe a commercial launch controller uses this approach.
Anything that prevents an accidental launch! I'm pretty sure this is even in the NAR safety code?

*looking*

Yes, yes it is: " I will launch my rockets with an electrical launch system and electrical motor igniters. My launch system will have a safety interlock in series with the launch switch, and will use a launch switch that returns to the “off” position when released. "

jrap330

Retired Engineer, NAR # 76940
TRF Supporter
All yours for the incredible price of \$19...

Joshua F Thomas

Well-Known Member
Hopefully it's a little more tidy than mine, which is quite a maze of wires! The amazon prime packaging foam in there is keeping the lithium batteries separated from the wiring to prevent any accidental shorts.

rklapp

NAR# 109557
TRF Supporter
Hopefully it's a little more tidy than mine, which is quite a maze of wires! The amazon prime packaging foam in there is keeping the lithium batteries separated from the wiring to prevent any accidental shorts.

View attachment 426428
The Amazon package is awesome.

Stolen...

rklapp

NAR# 109557
TRF Supporter
What did you use for the case/box?
Links in the description. Sorry couldn’t copy/past.