Stampede Wiring Question: Electronic component

Hey guys,
Ive recently upgraded my stampede to sgnerfs SMG stampede =P



anyways, just wanted to see if anyone else has done this and if so wat did they do with this little resister looking thing?



Im asking as my gun heated up badly at the back where this resister was and its fried...





Ive removed it and reconnected the wire without this peice and seems to run ok. Any insight would be greatly appreciated.

Thanks guys!
Richie

It looks like it is just a radio noise supressor. Not overly needed unless you like to shoot stuff while listening to the radio

Is that a resistor, or a capacitor? It's a little hard to tell from the pic.

Also, I'd be a little concerned personally. I've modded 5 Stampede's to 16.8v, and never had an issue with any of them over-heating, let alone melting any equipment. But all my connections have been made via the terminals on the battery sled.

Seeing as you're not using the battery sled, where have you connected the wire's from the battery pack to?

Cheers,

Hi Clunk,
Yeh my friend was playin with it and didnt load the darts properly so it jammed. And from wat i can see the motor kept tryin to run so it overheated and melt the component. I just connected the battery pack straight to the wires that were soldered to the old battery sled prongs (if that made any sense lol)

Seems to be fine now i think. I just wanted to see if that little component is unnecessary at all?

Hey, I'm a complete novice with electronic's, but I had a feeling that the piece in question was a capacitor, but I can't remember if it's connected to the + or - solder tail.

If it's connected to the negative terminal, then it's not a capacitor, and may be what Dietzie said.

Maybe someone like 238232 could shed some more light on this.

Cheers,

yeh same with me, Im pretty bad with component names. Anyways, if it helps the component is connected to the positive terminal before everything else.

resistor or current regulator of some sort. I think it reduces the current when the stampede draws too much. I asked my dad that question and that's what he said (he's builds electrical control systems).

You legend ungodlyfreak. Thanks for asking for me. So seems like I shud find some sort of current regulator? Or shud be ok without it?

Is it possible for you to get the heatshrink off so we can get a better look at the component?

Based on its position I'd go with some kind of resistor as well at a first guess, but I equally wouldn't be surprised if it were a diode.

yeh, that's what I meant, a diode, not a capacitor...

Crap, I really need to start playing with electronic's more!!

Cheers,

well the components fried so cant really see wat it is. But looking from these its the the yellow component under the big silver one at the 4cm mark)

That component under the silver one is a capacitor.

You said that it was connected to the positive terminal, was it connected...

Positive terminal - component - wire to rest of system

OR

Positive terminal - component - negative terminal

If the latter, then that makes sense, but if it's the former then that physically cannot work.

the capacitor is wired in series.

+ terminal - component - switch - motor - negative terminal

Well, it's not a capacitor then. A capacitor wired in that way would block pretty much all current from going past it.

Even if it's fried, any chance of a look?

cant seem to get a good shot of it. Just looks like a metal plate....

but heres wat its sposed to look like. Just above the bottom prong.

Well, I just got curious enough to open up my own Stampede. This is much more interesting than I anticipated.

The writing on it is:

JK16
250E

Googling JK16 helpfully turned up this page.

So it's a PTC self-resettable fuse (wiki link here). This is really neat, and helps explain a lot of things. Essentially this is a limit on how high a current (and implicitly, voltage) you can put through the Stampede. Presumably there's a similar component inside the Vulcan and the Barricade (e.g. why you can't put three 14500s in the Barricade). If you put too much current through then the resistance gets jacked up a lot (PTC stands for positive temperature coefficient), thus reducing the amount of current going through it, at which point the resistance drops again.

So... in response to the original question of whether you're fine without it, I'd say yes. Just don't expect to have a functional Stampede if you start experimenting on how high a voltage you can feed through it.

wow cheers for all your help mate! Thats really interesting that its got a fuse in it. Yeh i wudnt go any higher than the 4 batteries. I might swing by jaycar and replace it just in case it happens again :S Shouldve seen the gun wen it started heating up. Went bright red!! Sooo scary.... Is there anything else i can put in to ensure it doesnt heat up that crazy again?

I don't know if Jaycar sells those, you'd have to go to one of the proper electronics suppliers to find it. Here's one. If I'm reading the code on the one in the Stampede right that should be an acceptable substitute but I take no responsibility if things die/burn/explode on you.

Here's their search for all the PTC resettable fuses:

http://au.element14.com/ptc-resettable-fuses

Set the operating voltage to 16V (note that there's 16VDC and 16V, just select both). The specific part I linked you to had a holding current of 2.5A and a tripping current of 5A. If you want to play it safer you could dig around for something with a lower holding and tripping current.

Other than that, all I can really say is to remember that if things jam the absolute first thing you should do (and do it quickly!) is to flip the safety switch to break the circuit.

So that explains why my overvoltaged Barricade works longer before shutdown in colder weather.
It takes longer to heat up to the critical temperature for the PTC to kick in.

Good job, 238232.

See, I told you 238232 would get it sorted!!!

haha - our official electonic's guru!! Nice work mate.

Cheers,

Ahh, that is what the PTC is there for.

It is there to protect the motor from burning out. You often see PTC's in the wiring leading to an electric motor and its reason is simple, to protect the motor.

The PTC is a cheap component so therefore its better to burn out the PTC than to burn out the motors which cost a lot more.

So, if you want too run motors at high voltages and are prepared to risk the motor, simply remove the PTC and you will be able to do this.

Is it safer to buy the protected TR14500 batteries instead? Wat makes it different to the unprotected one?

rykitt wrote:Is it safer to buy the protected TR14500 batteries instead? Wat makes it different to the unprotected one?

Protected 14500 Li-on batteries cannot provide enough current to fire stronger springs like Servulus's or SgNerf's, you need unprotected version.

Protected cells have a PCB at the end that prevents (theoretically at least):

* Drawing too high a current.
* Discharging the cell under a certain voltage.
* Charging the cell over a certain voltage.

All of the above can lead to the cell being damaged over time in various ways. Unfortunately, as AA said this means that they can't provide enough current for the Stampede.

Or even enough current for a Barricade.

238232 - if I remove the plastic wrapping of a protected 14500, discard the PCB and connecting strip, add a magnet or similar for a positive nipple, and replace the wrapping with heatshrink, theoretically, it should work in our application?

I only ask, because I've got about 16 protected TF's, that I'd like to find a use for, rather than discarding them.

Cheers,

Yep, that should be perfectly fine.

Just make sure that you don't short +ve and -ve together, especially when you're adding the magnet.

If you short it and don't notice, it'll tell you real quick.

Thanks mate,

I'll just go google what you warned me about, so I have some idea in what you're saying.

But, yeh, had a mate do the Stampede voltage mod, and connected the battery to the wrong terminals on the sled (the linked end). When he connected the battery pack, he did learn very quickly that something was wrong.

Cheers,

Ooh, I just remembered another one. Keep the unwrapped batteries separate and ideally all pointing in the same direction if you're shelling a lot at the same time to reduce the chances of one rolling and shorting out another.

The cause behind both of these two is the same. From memory the outer casing of most batteries has the outer casing as one terminal, while the other is just a disc at the top, the clearance between them is rather small (given the battery dia it's kind of expected), so it's easy to short them if you're not attentive. If you open one up you'll see what I mean.

Thanks again mate,

I pulled one apart the other day, but didn't remove the PCB yet. Something I'll look in to once I've to an appropriate sized heat shrink. Don't really want to put alot of heat on the batt!! haha

Cheers,