Launch Control

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Here’s my DIY launcher. I have the battery pack on order. I thought I might try a 9v battery but determined that it won’t ignite the starters. So why will 4x 1.5v batteries ignite but not one 9v battery? What is the comparison in amps?

The delivered current can be calculated by dividing the battery voltage by the total resistance. The resistance is mostly summed up by the igniter resistance, the contact resistance of the alligator clips, the wire resistance and the internal resistance of the battery. 9V batteries usually contain 6 tiny AAAA cells, with lots of internal resistance (especially off-brand batteries). The 1.5V batteries are bigger and have less internal resistance.
If you really want to use 9V batteries, you can connect multiple ones in parallel (same brand and discharge state), but I wouldn't do it. If you need more power, you can replace your 1.5V batteries with 14500 size Li-Ion batteries. This will increase the power output a lot (higher voltage AND lower internal resistance), but not every launcher can handle them safely, so you would need to check that first before attempting it.

Reinhard
 
All batteries have an internal resistance. That internal resistance will limit the current that the battery can provide. Different battery chemistries have wildly different internal resistance. Lithium batteries have very little internal resistance so sometimes current limiting circuitry is built into lithium cells.
As Reinhard says the 9 volt battery you tried had a higher total internal resistance than the larger cells that you placed in series.
 
In answer to why a 9v won't work, look at this page on what's inside a 9v battery. Basically, a 9v is 6 batteries, all smaller than a AAA (AAAA? AAAAA?) Not enough current to work properly.
 
I previously looked up resistance comparison and 9v has 10x more than AA but in my head, I was thinking that more is better. Doh. Good thing I’m not a rocket scientist.
I previously looked up resistance comparison and 9v has 10x more than AA but in my head, I was thinking that more is better. Doh. Good thing I’m not a rocket scientist.
ohms law Current (I ) equals Volt/Resistance
 
Someone did the 9 v battery analogy a few weeks ago. I never knew it was made up of smaller batteries. They do fire the older ignitors. Nice looking box that is one big switch and contin light.
 
About a month ago, I built a mid power launch pad that is similar to one that Pratt Hobbies used to sell. Very inexpensive to build given the low cost of PVC.

I would like to build a 12 volt launch controller. I'm not sure exactly what specific components to buy and where to buy them. Years ago I used to do a lot of soldering so I am comfortable around a soldering iron.

Any input is appreciated.
 
Thanks for the information. You did a great job.
I would like to have a continuity light, a launch button and another switch that must be on in order to launch. I would like that switch to spring back to the off position after you release it. I like those launch buttons that have the cover that has to be lifted up.

Just wondering where people buy electronic parts these days? RIP Radio Shack.
 
Thanks for the information. You did a great job.
I would like to have a continuity light, a launch button and another switch that must be on in order to launch. I would like that switch to spring back to the off position after you release it. I like those launch buttons that have the cover that has to be lifted up.

Just wondering where people buy electronic parts these days? RIP Radio Shack.
All Electronics (www.allelectronics.com) is one place to get parts. eBay also has lots of options as well.
 
Over the years, I have settled in on 12V launcher systems. I make my battery connection to fit a lawn mower or car battery. I normally keep a battery in a home-built box with a handle-just for launches. Use a cheap mower battery from Menards. Replace it every 5 years. The alternative: just drive the mower or the car to the launch site. This works when I'm launching with the kids at home.
 
I built a 12v launch controller based on James Fletcher's design from this thread.

https://www.rocketryforum.com/threads/next-launch-controller.34774/post-329902

Just make sure that you use relays that are designed to work with LEDs and other lower current devices. These types of relays have an internal diode.

I also used a 12v 7AH lead acid gel battery like those used in computer UPS's. Around $20 new.
 
Thank you all for your replies. Very helpful.
OverTheTop asked about Fry's. We used to have one around the Boston area but I think they are long gone.

Someone in my club mentioned You Do It Electronics in Needham, MA.
If I went over with a diagram, I wonder if they would be able to grab the parts for me?


Check out the diagram at 1:53. That looks like what I would want to do. Seems simple enough.
 
Someone in my club mentioned You Do It Electronics in Needham, MA.
If I went over with a diagram, I wonder if they would be able to grab the parts for me?
Not if it's the diagram at 1:53 in the video, which just shows generic symbols for all the components. For each of them, there are about a 6.4 million (I counted) variations available. You'll need to get a whole lot more specific than that, if not actual part numbers than at the very least some reasonably detailed specs for each part.
 
Not if it's the diagram at 1:53 in the video, which just shows generic symbols for all the components. For each of them, there are about a 6.4 million (I counted) variations available. You'll need to get a whole lot more specific than that, if not actual part numbers than at the very least some reasonably detailed specs for each part.
I was hoping I could go to an electronics store, tell them I want to build a 12 volt system and give them a description of each part in addition to the diagram.
Work Box
Push button switch
Toggle switch that springs back
Resistor (I think he uses 2 Ohms)
LED
Wire
Aligator clips
Male and female banana connectors (Am I describing that correctly)
Some kind of connector for the battery.
I need a soldering iron. My soldering gun from 1964 doesn't heat up anymore.
Solder.
 
I was hoping I could go to an electronics store, tell them I want to build a 12 volt system and give them a description of each part in addition to the diagram.
You can try, but in my opinion that is somewhat above and beyond what I would ever ask for in a store. Those folks are unlikely to have any idea about the behaviors and requirements of a launch controller. A few of the items they could guide you to (work box, soldering iron, solder) but not everything else. IMHO.

If you're not familiar enough with electronics to at least be able to spec out those parts, I would suggest working from a more detailed plan that gives a detailed parts list.
 
Does Aerotech still sell their launch controller? (controller, not the Mantis launch pad) It is ideally set up to run from any number of power sources and is a good option for personal launches. I have one and just thought about switching the power connections from the alligator clips for a car battery to a set of Deans plugs so I can use a 3S 50C 6000mAh battery pack I have.
 
You can try, but in my opinion that is somewhat above and beyond what I would ever ask for in a store. Those folks are unlikely to have any idea about the behaviors and requirements of a launch controller. A few of the items they could guide you to (work box, soldering iron, solder) but not everything else. IMHO.

If you're not familiar enough with electronics to at least be able to spec out those parts, I would suggest working from a more detailed plan that gives a detailed parts list.

I was thinking about when I go to the Micro Center computer store. I give them a list, we discuss the brands and what the computer will be used for. Then we walk around the store with a basket, the sales consultabt helps me pick out what I need, and I'm off to build the computer.
 
Does Aerotech still sell their launch controller? (controller, not the Mantis launch pad) It is ideally set up to run from any number of power sources and is a good option for personal launches. I have one and just thought about switching the power connections from the alligator clips for a car battery to a set of Deans plugs so I can use a 3S 50C 6000mAh battery pack I have.

I think I know the one you are referring to.
https://www.siriusrocketry.biz/isho...MItdWB5pzk6gIVuQiICR2CwAiSEAYYASABEgKJ_vD_BwE
It is impressive looking. Thanks for the advice.
 
I was thinking about when I go to the Micro Center computer store. I give them a list, we discuss the brands and what the computer will be used for. Then we walk around the store with a basket, the sales consultabt helps me pick out what I need, and I'm off to build the computer.
Not the same thing, unfortunately. IMHO.
 
Unless you're lucky enough to live close a place like Orvac Electronics in SoCal, storefront electronics stores are few and far between. Fry's is getting out of the parts business, so you can scratch them off the list. Apparently they'd rather lose money on major-brand appliances and consumer electronics than make money on high-margin parts... that's what killed off Radio Shack.
 
Thanks for the information. You did a great job.
I would like to have a continuity light, a launch button and another switch that must be on in order to launch. I would like that switch to spring back to the off position after you release it. I like those launch buttons that have the cover that has to be lifted up.

Just wondering where people buy electronic parts these days? RIP Radio Shack.
There were a few discussions this week on launch controllers this week..do a search on the forum....the initial topic was on clustering and Estes PSII controller. It has been brought up numerous times this year...
 
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