SCADAman's 4 Banger Launch Controller

[scadaman29325]

I'm having a problem figuring out the wiring and need some help. The biggest issue is the toggle switches with built in LEDs. I had schematic in mind, but realised the switches wouldn't work as I intended. I know there is a way, but need more brain power. KEY FACTOR, I like the components I have and may need to add a set of LEDs get this to work, but REALLY don't want to start all over with other parts. Just need to figure it out.

Among others, one thing I'm trying to figure out is why are the LED switches doing what they do. This is what's happening. Positive and negative go to switch, flip the switch, LED turns on and positive is supplied to ACC+ terminal. Simple enough. But if i connect a jumper between positive and ACC+ it sparks and the wire heats up considerably.

Truthfully I dont remember why I tested this, but still the question remains, why is the jumper heating up? It the positive terminal on the switch jumped to the ACC+ terminal. Seems like it would be just bypassing the LED. What is the internal schematic of the switch? I've drawn it out several different ways and cannot see the reason for this.

I'm going to have to rewire. For now I connected B+ through the disconnect and then to all switches, and negative to all switches. Insert key and turn, Fire Missiles lights up. Flip toggle switches and they light up.

I will be installing LEDS (and buzzers?) for continuity test. The idea was to flip on the desired toggles, one or all, press Fire Missles, then watch them fly.



Anyways, here it is.
















Launch Controller
Battery 12v 7Ah(?)
Plastic ammo box
Battery disconnect switch with key
4 Toggle switches with built in LED
"Fire Missiles" pushbutton no/nc switch with built in LED
14 ¼" tab connector
3' Red, Green, Blue, Yellow, Orange, Black project wire

 

[scadaman29325]

Here's the initial schematic before I realized the switches didn't work the way I thought. (Disregard thick vertical line at top)

 

[scadaman29325]

Oh yes, I'll be cutting Ext Cords in two and connecting the female ends of 4 Ext Cords to the box, about 1ft. The 14ft male ends will have alligator clips installed on the bitter ends.

 

[mikewrt]

What is your intention with the LEDs built into the toggle switches? Do you want them to illuminate to show the pad is selected or as the continuity indicator on that pad?

I have another thought on the extension cords .... you might consider installing a pair of duplex outlets on the back of your box or individual panel mount female receptacles rather than have 1' dongles hanging out the back. I used a panel mount female receptacle and like it. I try to get a photo of my controller tomorrow.

 

[scadaman29325]

Initially I was thinking continuity, but that was my first issue with the switches. I was going to let the toggle bypass the LED and use a pushbutton to fire the rocket.

The thought was to select the rockets I wanted to fire by competing the circuit on negative side.
Edit: Oops, that's not right, what was I thinking?


Then, I was going to add a seperate LED/beeper for Continuity, and/or momentary pushbutton LED for that, and that's when things fell apart.

 

[mikewrt]

I'm not familiar with your toggle switches but based on what I can see from the photo of the switch above I believe I can write a schematic to to use the built-in indicator for either continuity or simply a pad selection indicator. This is assuming the switch output is truly open when the switch is off. Also do you know for certain the built-in indicator is a led or a lamp?

Guess you need to decide how you want it to work.

If you use it for pad selection then you will want separate continuity indicators for each pad.
If you use it for continuity you must do some testing to understand how much current the indicator draws. The current draw during continuity check must be well below the threshold to activate the igniter plus plenty of margin to avoid accidentally firing before commanded.

 

[scadaman29325]

Agreed.

And now I have some 12v tone alarms, "beepers" and a 4ch remote control I got for Christmas. I'm rethinking the project and may not use the Fire Missiles button. But it does look cool! I'll be adding a seperate LED/Beeper and 'push to test' button for each circuit.

Something like this.

 

[caveduck]

We have that "fire missiles" button in the DART launch pad - the kids love it. It's not super beefy and I kinda figured it would be the first thing to fail, but it's still going strong after ~5000 launches in 3+ years. It does not carry all the current though, it's only used to trigger a solid state relay. It's wired up so that the launch button LED is on whenever the panel is armed with the safety switch.

If you're using a piezo buzzer I'd suggest making it be "on" continuously whenever the circuit is armed and in a state where pushing the button will deliver current to the clips. You can do this by moving the left leg of the buzzer to the left hand terminal of the launch button. In the drawing above, there is no indication of a "hot pad" unless the momentary test button is actively depressed.

For your continuity checking, I'd recommend keeping the continuity current < 50 mA. The no-fire current of most of the ignitors we use is up around 200 mA, but you want a wide margin of safety.

 

[scadaman29325]

This is a little better drawing. I think this works all the way around. Firing one at a time selected by LED Toggle switch using the remote control, and fire multiple rockets per selection with Fire Missles button.



LED Toggle Switch supplies b+ and is an indicator of selected pad.

Test Pushbutton connects b- through Test LED and buzzer to igniter. B+ already selected above.

Fire Remote Control puts b- straight to igniter and launches rocket.

With desired pads "selected", Fire Missles Pushbutton supplies b- to all pads. Those NOT "selected" cannot fire due to no b+ at the igniter.

PLEASE punch holes in my logic and schematic.

Agreed on the 50ma. I'll have to measure the current when connected and add resistors as needed.

Fire Missles PB is rated for 5 amps. I'm thinking that should be PLENTY for multiple clustered rockets.

Hmm, just realised I didn't put the battery disconnect in the drawing. When battery is connected Fire Missles glows blue.

THANKS!

 

[scadaman29325]

Crap, a couple of problems related to Fire Missiles button using a common b- to all circuits.

If #1 test good, #2 will test good even without an igniter.

Also, if 1 & 2 are selected, firing either by remote control will launch both.

Solution, remove the common b- between all circuits coming from Fire Missiles button.

Back to the drawing board, literally.

I could install a diode between circuits.

 

[Handeman]

I ran into the same issue with an 8 pad controller for our club. The circuit that works perfectly for a single pad, cross feeds power or ground to the other pads when done in parallel.

Here is the schematic of our club box. I used relays. They all activate with the ARM and LAUNCH button are pressed down, but power and return are available to the igniter only if the Pad Switch is ON. It does allow selecting multiple pads to launch at the same time. The pad switch also isolates the continuity LED. That was another problem without the relays, if you had continuity on one, all the LEDs would light.

BTW, the ARM and LAUNCH switches are large 2.5" dia. lighted pushbutton switches and both have to be pushed to launch. They are far enough apart that you can't operate both with one hand. It makes the launch function a two handed function that we felt was safer. It also allows the LCO to let kids launch their own rocket by pushing the LAUNCH button, but the LCO has control of the ARM button to prevent the launch before the countdown. Some of the smaller kids get a little quick on the button sometimes.

The schematic shows 115VAC receptacles instead of igniters because we use a bundle of 50' 16 GA orange extension cords with the clips on 6' lamp cord wires with plugs (clip whips). We can swap out clip whips easily if stop working for any reason. Also the 50' makes it easy to setup up +30' for safe distance D - G motors, although we seldom allow that large of motor on the low power pads. We usually have three 1/8" rods, two 3/16" rods, one 1/4" rod and two 1010 rail pads. The 1010 get a lot of use by the TARC teams.

Everything is contained in a plastic tool box. The receptacles are on the back of the box.

 

[mikewrt]

SCADAman, I promised a photo of my controller showing the surface mount receptacle a week ago and just finally got around to it. See the receptacle in the lower right hand corner of the picture below. I use a 25 to 50 foot extension cord to the pad. From the extension cord to the igniter I use a standard PC power cord with the IEC end cut off and replaced with clips. My controller is built in box similar to yours, I use a 20v Li-Ion cordless drill battery that fits nicely inside.

 

[scadaman29325]

#Handeman, agreed, to avoid the cross feed I think I'm going to use a power strip plugged into 1 of the outlets for a rocket race. I may play around with diodes later. BTW, clean looking drawing. I found a nice EASY TO USE online dwg tool at digi-key.

#Mikewrt, I think I'm going with 2 duplex outlets similar to yours (rectangular vs std outlet). Very nice looking build too. I had an extra green ammo box on hand, if I had not, I would have purchased orange.

Thanks

 

[Blast it Tom!]

I have to study up on this stuff as well. I only want to arm one pad, but be ready to handle cluster launches, and check continuity on each motor individually before launch. I was going to buy a key switch to lock out all power, I have a momentary to send the big power, it's the continuity that's messing me up - but thanks for the 50 mA note...!

 

[Voyager1]

As an example of how a typical relay-based 4 channel launch controller could be wired and configured I present a 4 channel version of our club's 8 channel system. This might give you some useful ideas for your own 4 channel launch controller. This system has a low power launch control box connected by a 30m (60m and 90m, if necessary) multi-core field cable to a 4 channel high current pad box. This configuration allows for selection of 1 to 4 channels to be fired with continuity feedback from each of the pad box outputs.



The continuity, arm and launch momentary switches are illuminated when pressed, although this is not indicated in the schematic. Pressing the continuity button on the LC box sends approximately 20 mA through each igniter that is present on the pad box. At this stage the ignition relays in the pad box are in the N/O (normally off/open) position which allows continuity sensing.

Ignition channels are selected by the SEL switches on the LC box. The ARM button arms the pad ARM relay to supply 12V to the 4 ignition relays. The ARM and LAUNCH momentary buttons are depressed simultaneously to launch.

The LC box can use a 12V 1Ah gel cell; the pad box uses a 12V 7Ah gel cell. We do have 70cm RF modules that replace the field cables and make it much more convenient, particularly for the 60m and 90m pads.

Here are our club's 8 channel LC box and and one of our 4 channel Pad boxes.

 

[scadaman29325]

VERY NICE circuit! What size wire are you using between the DB9(?) connectors? I would think some Cat 6 might work since the current would be minimal, but need at least 10 conductors, 1 for common/ground. So maybe a VGA cable DB15? I may have a 50ft one of those available. Hmmm...

Thanks

 

[Voyager1]

The field cable is a 9 conductor (28 AWG) with foil and drain wire, so yes, 10 conductor. Just perfect for this application. Each conductor is multi-strand, so it's nice and flexible. I'm able to use the DB9 connectors as long as there is a solid connection with the connector bodies, as it is the common conductor connected to the drain wire. This means you really need to use the jack screws to secure the connectors to their mating connectors.

This 8 channel control system has been in use by our club for 6 - 7 years and has been very reliable. A couple of years ago I built the RF modules to replace the field cables. These RF modules just plug into the LC and pad boxes in place of the cables.

I notice that the schematic is not very clear in the post. I can send you a clearer copy if you like.

 

[scadaman29325]

Yes, if you would, please send a clear copy. I'd like to see the part number on those diodes.

I REALLY APPRECIATE the help! THANKS!

 

[Voyager1]

Try this PDF. The LEDs I use are 12V rated with a series resistor installed in one of the leads. They are similar to these:

https://www.amazon.com/Laliva-yellow-orange-Pre-Wired-Chrome/dp/B07QNWSXX6?th=1

and exactly these:

https://www.jaycar.com.au/12v-mini-chrome-bezel-red/p/SL2644
and
https://www.jaycar.com.au/12v-mini-chrome-bezel-green/p/SL2645

 

[scadaman29325]

Perfect. Thanks again!

 

[Blast it Tom!]

*Whew* been away for a while... building rockets and working. Thanks for the guidance, this dumb ol' mechanical engineer is ready tor foray once again into the electrical arena!

 

[BMcD]

Excuse an ignorant question - what is the purpose of the diodes on the pad side?

 

[scadaman29325]

Excuse an ignorant question - what is the purpose of the diodes on the pad side?

GLAD you asked, I used to know, and just then wondered why myself, getting old-er...

Found this:
https://electronics.stackexchange.c...a-diode-connected-in-parallel-to-a-relay-coil

The diode is a really good idea. It's called a freewheeling diode. This answer covers the details (and that's why I put this as a comment only): electronics.stackexchange.com/a/56323/930 Scroll to where it says "Some Background Info". In short, the diode takes the energy stored in the relay's coil when you switch the current off. Without the diode, the energy has no place to go and will cause a large and probably destructive voltage spike. – zebonaut Feb 18 '14 at 11:26

 

[Voyager1]

GLAD you asked, I used to know, and just then wondered why myself, getting old-er...

Found this:
https://electronics.stackexchange.c...a-diode-connected-in-parallel-to-a-relay-coil

The diode is a really good idea. It's called a freewheeling diode. This answer covers the details (and that's why I put this as a comment only): electronics.stackexchange.com/a/56323/930 Scroll to where it says "Some Background Info". In short, the diode takes the energy stored in the relay's coil when you switch the current off. Without the diode, the energy has no place to go and will cause a large and probably destructive voltage spike. – zebonaut Feb 18 '14 at 11:26

Yes!

 

[Greg Furtman]

Where did you get the "Fire Missile" switch?

 

[scadaman29325]

Where did you get the "Fire Missile" switch?

There is a variety on Amazon. That's where I got mine.