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Old 12-27-2011, 01:08 PM   #1
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Is this capacitor fully needed?


Hi everyone,
I'm into estes model rocketry and am currently trying to wire a wireless controller for the ignition. I am re-purposing a R/C car to be the brains of the operation.

However, I've run into some issues with the controller fitting into its new case(a Radioshack project box 3x2x1). I could easily chop off part of the board to fit it, but i run into a capacitor that i guess is just used for security of the batteries. Ive obtained the schematic off of the FCC ID and would be happy to share.

The capacitor in question is labeled "C1" in the top middle of the drawing( or far right middle, sorry the pdf is rotated). The parts list from the FCC account says "C1-104(0603)". Can this be removed and ignored? Or is it extremely needed?

Heres the pdfs
Schematic - https://apps.fcc.gov/eas/GetApplicat...tml?id=1045910

Parts - https://apps.fcc.gov/eas/GetApplicat...tml?id=1045908

Internal Photos - https://apps.fcc.gov/eas/GetApplicat...tml?id=1045913

C1 on the board is just off the negative battery input.
Thanks for your time, and helping a newbie.

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Old 12-27-2011, 01:49 PM   #2
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Is this capacitor fully needed?


can't view any of your links.

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Old 12-27-2011, 01:56 PM   #3
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Is this capacitor fully needed?


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Originally Posted by bob22 View Post
can't view any of your links.
I am so sorry, I've attached them now.
Attached Files
File Type: pdf Shematic.pdf (26.0 KB, 66 views)
File Type: pdf Parts.pdf (34.8 KB, 94 views)
File Type: pdf Photos.pdf (63.1 KB, 55 views)
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Old 12-27-2011, 01:59 PM   #4
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Is this capacitor fully needed?


Well.....look at it this way....considering how manuf are trying to keep costs down, I doubt they are going to add something that is not really needed......I would not remove it.

But.....you could unsolder it....attach a couple of insulated wires to it and relocate it.
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Old 12-27-2011, 02:10 PM   #5
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Is this capacitor fully needed?


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Well.....look at it this way....considering how manuf are trying to keep costs down, I doubt they are going to add something that is not really needed......I would not remove it.

But.....you could unsolder it....attach a couple of insulated wires to it and relocate it.
Yeah, i thought that too, but I really have no good idea how to desolder a surface mount component. Too darn small.

Upon closer inseption, it seems damaged slightly, the plastic cover is chipped and wire is exposed...
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Old 12-27-2011, 02:55 PM   #6
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Yeah, i thought that too, but I really have no good idea how to desolder a surface mount component. Too darn small.

Upon closer inseption, it seems damaged slightly, the plastic cover is chipped and wire is exposed...
Any tips on how to desolder a surface mount component?
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Old 12-27-2011, 03:02 PM   #7
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Is this capacitor fully needed?


Solder wick.....it looks like braided copper strap...but real small.
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Old 12-27-2011, 03:04 PM   #8
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Is this capacitor fully needed?


I think you'll find it won't work without it.
Dawg's suggestions are good ones.
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Old 12-27-2011, 03:19 PM   #9
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Is this capacitor fully needed?


BTW...don't use a big honking iron....you will distroy the cap and board....a pencile iron will work fine.....

In case your wondering....surface mount components are typically soldered using a solder bath (production line) or hot air....real hot air.
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Old 12-27-2011, 03:24 PM   #10
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Originally Posted by ddawg16 View Post
BTW...don't use a big honking iron....you will distroy the cap and board....a pencile iron will work fine.....

In case your wondering....surface mount components are typically soldered using a solder bath (production line) or hot air....real hot air.
I have a 30W radioshack pencil iron, now im really worried about ruining the little dot capacitor.
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Old 12-27-2011, 04:00 PM   #11
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Is this capacitor fully needed?


Redid it all and it wont work anymore...

Thanks anyways guys!
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Old 12-27-2011, 06:00 PM   #12
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Is this capacitor fully needed?


Can you give better pics of what you're doing and how you're doing it.

I've taken a few soldering classes, and a few ET classes.

You can't possibly damage a circuit to where it's inoperable. Anything/everything can be fixed.

How to desolder a capacitor


Explain the exact problem, and post photos of the exact circuit, with details of what you did.
EDIT

This is how to solder on a new capacitor.



To reroute a new conductor pathway, just strip tiny bits of 14 awg wire (or 16, or 20 depending on the charge of the capacitor) and you can solder that wiring onto the point to make an electrical connection. Just make sure you have the ends facing the appropriate direction between the negative and positive feeds

This is a good vid for someone who doesn't know how to solder, it's a very generic, basic instruction how to go about doing it.

http://www.youtube.com/watch?v=ieoM_...eature=related

Last edited by BigGuy01; 12-27-2011 at 06:08 PM.
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Old 12-27-2011, 09:26 PM   #13
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Is this capacitor fully needed?


Good Lord






And that's all I've got to say.....about that.
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Old 12-27-2011, 09:30 PM   #14
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Originally Posted by BigGuy01 View Post
Can you give better pics of what you're doing and how you're doing it.

(I shortened the post)

This is a good vid for someone who doesn't know how to solder, it's a very generic, basic instruction how to go about doing it.

http://www.youtube.com/watch?v=ieoM_...eature=related
Thank you for the helpful tutorials, but the capacitor in question is a surface mount without a large cap. It has somehow been damaged and i think my sketchy desoldering finally broke it. The research to find and cost of shipping of an identical part just isn't plausible.

But I did learn how to desolder caps, which is always helpful.
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Old 12-27-2011, 11:29 PM   #15
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Is this capacitor fully needed?


C1 is a bypass capacitor. It is the least necessary capacitor in the circuit, and it should theoretically work without it. But it probably won't. I would not recommend removing it, unless you replace it in a different location. Regardless, the capacitor is not your biggest problem. I have a lot to say about wireless launch controls:

As Greg said in the other thread, this isn't the best approach to building a wireless launch controller - something I've built a few of myself. You could do it with this hardware, but I wouldn't advise it. Safety is the biggest concern when building any launch controller, and a wireless one introduces new issues. A radio glitch igniting a K-class composite rocket motor while you're standing near the pad could be disastrous.

With that said, I definitely think you should build a wireless launch controller. They're really cool, convenient to use, and safe when properly implemented.

Now I'm going to briefly summarize everything I know about wireless launch controller design.

My approach to designing a safe wireless launch controller includes three independent safety elements: Interference rejection, control redundancy, and physical separation.

Interference rejection is very important. Many radio control devices, like the one you have, are not designed to prevent accidental activation. In fact, many systems are designed to prioritize sensitivity over interference rejection. Nikko would rather have your RC car work at somewhat longer range at the expense of it occasionally acting crazy. They certainly won't spend any additional money on things like encryption to ensure that someone else's controller won't operate your car. In fact, chances are that every controller like that one will operate your car. If that doesn't scare you about launching rockets with it, then find a different hobby.

You need a radio system with encryption. Modern garage door openers, vehicle alarm controllers, vehicle keyless entry systems, and remote engine start controllers are perfect for this. They prioritize security over range and cost. A remote start kit is probably the easiest way to accomplish what you need. They often have multiple control channels and long range. Some even have two-way communication, which is necessary if you want to be able to do continuity checking. Which you definitely should.

The second safety factor is control redundancy. You do not want a single button press to launch the rocket. You NEED to have an arming control separate from the fire control. Ideally, the arming control should not only require you to press an arm button before firing, but should actually activate a separate relay that un-shunts the firing circuit and connects the firing battery to the final firing relay. This is not hard to do.

The final safety factor is physical separation. Your "wireless" firing system needs to have some wires. You want enough separation between the pad and the firing controller that you can connect a cable set to the igniter first, then to the launch controller second, without the risk of injury if the rocket accidentally fires. This also protects the controller from damage due to rocket blast. The length of this cable could be anywhere from 10 to 100 feet or more, depending on the size of the rocket being launched.

So my final recommendation is this: Begin with a two-way remote vehicle start controller or alarm controller. Use one of the control channels (perhaps intended for activating lights or something) to operate a SPDT relay as an arming control. In the de-energized position, the relay shunts the positive firing lead to ground. In the energized position, the relay connects the positive firing lead to the positive battery terminal through a resistor for continuity checking. Something around 1K should be good for a 12V battery, giving a 12mA continuity check current. Use one of the two-way return channels on the remote start controller (perhaps the one intended to tell you if your lights are on) to read the voltage on the battery-side terminal of the relay. It will show 12V (a "lights on" reading) before arming the system, and zero when armed if the igniter has continuity. Use a different control channel to activate a second relay which closes across the continuity checking resistor to fire the igniter. This is merely a wireless version of the most basic Estes launch controller circuit.

Be sure you have a manual arming switch on the device as well which completely disconnects the battery and shunts the two firing leads together. Install a loud audio alarm on the device that alerts you when it is manually armed. You may also want to install an alarm on the firing terminals, but this complicates the continuity checking system (it is a solvable problem, but can be challenging).

You can get much fancier than this, and there are plenty of other ways to do it. However, any safe system incorporates all of these safety measures.

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Last edited by mpoulton; 12-27-2011 at 11:45 PM.
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