String Task

jinhusong
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Re: String Task

Post by jinhusong » December 7th, 2018, 9:34 am

Last time, the kids here used relay to control the nichrome. Then a limit switch to cut the power to it after next task started.

This time, no single battery bonus, maybe you can use dedicated battery for it.

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Re: String Task

Post by ScottMaurer19 » December 7th, 2018, 7:17 pm

jinhusong wrote:Last time, the kids here used relay to control the nichrome. Then a limit switch to cut the power to it after next task started.

This time, no single battery bonus, maybe you can use dedicated battery for it.
I can confirm i had to use a separate battery for this
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Re: String Task

Post by Flavorflav » December 9th, 2018, 3:16 pm

absolutezerok3 wrote:
honorstoise wrote:How long does it take for nichrome wire to break a fishing line or string
It should be almost instantaneous. Otherwise, you probably don't enough current to sufficiently heat up the wire.
Many years ago we made one suck up some time - can't remember how much, exactly, but probably at least ten or fifteen seconds. There's no particular reason to want to do that this year unless you don't have a good timer, but it is possible with a battery with a high capacity and a low C rate.

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Re: String Task

Post by dragonfruit35 » December 10th, 2018, 6:59 am

Flavorflav wrote:
absolutezerok3 wrote:
honorstoise wrote:How long does it take for nichrome wire to break a fishing line or string
It should be almost instantaneous. Otherwise, you probably don't enough current to sufficiently heat up the wire.
Many years ago we made one suck up some time - can't remember how much, exactly, but probably at least ten or fifteen seconds. There's no particular reason to want to do that this year unless you don't have a good timer, but it is possible with a battery with a high capacity and a low C rate.
Be careful with that- I'd think there's a definite case for that to be considered an electrical timer if it ran for more than 10 seconds.

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Re: String Task

Post by erico.vert » December 10th, 2018, 5:00 pm

dragonfruit35 wrote:
Flavorflav wrote:
absolutezerok3 wrote: It should be almost instantaneous. Otherwise, you probably don't enough current to sufficiently heat up the wire.
Many years ago we made one suck up some time - can't remember how much, exactly, but probably at least ten or fifteen seconds. There's no particular reason to want to do that this year unless you don't have a good timer, but it is possible with a battery with a high capacity and a low C rate.
Be careful with that- I'd think there's a definite case for that to be considered an electrical timer if it ran for more than 10 seconds.
Would definitely think that would be an electrical timer

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Re: String Task

Post by C8H10N4O2! » February 4th, 2019, 1:25 pm

If I have the nichrome wire in a closed circuit for almost the entirety of my run time (it's the 1st action), would that be considered 'unsafe' operation? It glows pretty brightly when the circuit is closed. I'm trying to find a place for a parallel action to shut it off (allowed by the FAQs), but am having trouble.

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Re: String Task

Post by PM2017 » February 4th, 2019, 2:26 pm

C8H10N4O2! wrote:If I have the nichrome wire in a closed circuit for almost the entirety of my run time (it's the 1st action), would that be considered 'unsafe' operation? It glows pretty brightly when the circuit is closed. I'm trying to find a place for a parallel action to shut it off (allowed by the FAQs), but am having trouble.
Our alternate team had the genius idea of having a battery power the nichrome being held up by the line thats broken. As soon as the line breaks and the battery falls, the circuit is disconnected. The falling battery acts as a weight and initiates the next action.
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Re: String Task

Post by Dreamz » February 20th, 2019, 4:03 pm

Hey guys, I'm currently passing current directly from a 9V battery through a ~2cm length of 38 AWG nichrome (pretty darn thin). The way my machine is built is that the current stops immediately after the string is broken, so the wire only glows red hot for a fraction of a second.

However, I would like to make some changes to my machine that would essentially keep the current running through the (glowing) wire for a good while (~1 minute). Would my wire potentially burn out and break? Will safety be an issue? Should I add a resistor?

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Re: String Task

Post by C8H10N4O2! » February 20th, 2019, 5:51 pm

Dreamz wrote:Hey guys, I'm currently passing current directly from a 9V battery through a ~2cm length of 38 AWG nichrome (pretty darn thin). The way my machine is built is that the current stops immediately after the string is broken, so the wire only glows red hot for a fraction of a second.

However, I would like to make some changes to my machine that would essentially keep the current running through the (glowing) wire for a good while (~1 minute). Would my wire potentially burn out and break? Will safety be an issue? Should I add a resistor?
For whether or not the wire will break, I believe testing it is the best answer (unless you have limited amounts). Same answer for the resistor question.
As to whether or not safety is an issue, if the wore is only glowing, and not near anything flammable, I do not see why it is a safety issue. In VA at least, I asked the ES if it would be (I have a kill switch to turn off the nichrome), and they said that they have no problem with it glowing for the duration of my run, and if i really wanted to, I could turn it off without counting it as a touch if the kill switch did not work.
While this is obviously only the VA ES's perspective, I cant imagine that many others will think a glowing nichrome wire is a big deal... after all they did use to have actual matches and flames in mission possible.

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Re: String Task

Post by Dreamz » February 20th, 2019, 5:57 pm

C8H10N4O2! wrote:
Dreamz wrote:Hey guys, I'm currently passing current directly from a 9V battery through a ~2cm length of 38 AWG nichrome (pretty darn thin). The way my machine is built is that the current stops immediately after the string is broken, so the wire only glows red hot for a fraction of a second.

However, I would like to make some changes to my machine that would essentially keep the current running through the (glowing) wire for a good while (~1 minute). Would my wire potentially burn out and break? Will safety be an issue? Should I add a resistor?
For whether or not the wire will break, I believe testing it is the best answer (unless you have limited amounts). Same answer for the resistor question.
As to whether or not safety is an issue, if the wore is only glowing, and not near anything flammable, I do not see why it is a safety issue. In VA at least, I asked the ES if it would be (I have a kill switch to turn off the nichrome), and they said that they have no problem with it glowing for the duration of my run, and if i really wanted to, I could turn it off without counting it as a touch if the kill switch did not work.
While this is obviously only the VA ES's perspective, I cant imagine that many others will think a glowing nichrome wire is a big deal... after all they did use to have actual matches and flames in mission possible.
Thanks for the suggestions! My main concern though is that the battery may not be able to withstand a long nichrome action duration for more than a few trials. Would it cause the battery to overheat and possibly blow up? Don't want to test that one for obvious reasons....

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