Will this work?

computer guy

Hi there everyone,

I am creating a box to light some matches.
The matches are wound in nicrome wire.

I am wanting a led to light when the fire button is pressed and go out when the wire has broken.

Will this circuit work?
I don't think it will but can't think of an easy way to make it work.



Thank you

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Building Blocks To The Propeller Chip A web site designed to help people who are new to the propeller chip.

Guitar Hero controller using the prop (WIP) --> HERE

PJAllen

No, it won't work.

Both ends of the R1-LED1 circuit are always at GND.

Leon

Moving the LH R1 connection to the other side of the 'match' will work.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Phil Pilgrim (PhiPi)

Simply moving the LED circuitry to the other side of the match will only indicate whether the button is pressed — not whether the nichrome wire has broken.

What you really need is a current sensor, wherein the LED lights up when the nichrome wire is drawing current. The attached circuit should do this. You will need to select a value for R such that when the wire is fully incandescent, the voltage drop across R is at least 0.6V. This will cause the transistor to conduct and the LED to light. When the wire breaks, the transistor's base is pulled back to the positive supply, causing it to shut off and the LED to go out. Also, make sure resistor R is rated for the wattage it will be dissipating. You don't want it to become incandescent as well!

-Phil

Dgswaner

sooo, you've peek my curiosity, any more info on what your building?

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

computer guy

I am creating a way to light gun powder and other cool explosive/flammable materials from a distance in a given order.

I have a match, with the tip wrapped in nicrome wire. When current is passed through the wire it heats up and lights the match.
Looks cool.

Thank you

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Building Blocks To The Propeller Chip A web site designed to help people who are new to the propeller chip.

Guitar Hero controller using the prop (WIP) --> HERE

Franklin

Passing a LOW voltage LOW current signal through the match and testing for a loop would work

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- Stephen

computer guy

I am wanting to use as little components as possible and only use parts I have already.
I am using a 12v battery to light the match (probably not necessary but it does the job).

The only regulator I have is an LM1086 5v regulator. I am assuming this would probably still heat up the wire.
The wire I am using is copper wire from a multi stranded wire. So it is really thin. I would guess about 0.2mm - 0.4mm.

I like the idea of the current sensor and the idea of using a low voltage low current to test for a loop.

The only problem I see with the current sensor is that if R is to high a value the wire may not heat up.
Also how would I find the value of R without going through lots of wire and the risk of melting my breadboard?


Thank you

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Building Blocks To The Propeller Chip A web site designed to help people who are new to the propeller chip.

Guitar Hero controller using the prop (WIP) --> HERE

computer guy

I just tested the following circuit and it seems to work.
What are peoples thoughts on it?



Thank you

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Building Blocks To The Propeller Chip A web site designed to help people who are new to the propeller chip.

Guitar Hero controller using the prop (WIP) --> HERE

sam_sam_sam

computer guy

What you have will work and should work good

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··Thanks for any··that you may have and all of your time finding them

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Sam

computer guy

Thanks. I was hoping that would be the case.

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Building Blocks To The Propeller Chip A web site designed to help people who are new to the propeller chip.

Guitar Hero controller using the prop (WIP) --> HERE

PJAllen

It seems to "work"?

When the switch is open, the LED/resistor will conduct through the wire/element.· When the switch closes it presents a short across the LED/resistor.· So, the LED will be on till the switch is closed.

Phil Pilgrim (PhiPi)

computer guy (in his first post) said...
I am wanting a led to light when the fire button is pressed and go out when the wire has broken.

Even though your latest circuit doesn't satisfy your original specs, as long as it works for you, that's all that matters. The only catch, of course, is that you can't know if the wire is broken until you turn off the switch.

-Phil

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'Still some PropSTICK Kit bare PCBs left!

computer guy

I basically want the led to show if the wire has broken.
The switch will only be closed for a short period of time (less than 3 seconds).


Thank you

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Building Blocks To The Propeller Chip A web site designed to help people who are new to the propeller chip.

Guitar Hero controller using the prop (WIP) --> HERE

GICU812

What would happen if you put the LED and resistor in paralell with the heating wire? Wouldnt the electricity in theory take the easier path through the wire, and only pass enough power through the LED when the wire was broken?

I just dont know how much resistance is in the heating wire when its red hot, it might be enough to light the LED. Im basing this on how you calculate the resistance of 2 resistors in paralell, but assuming the heating wire would be 0 ohms, at least until it warmed up, then I dont know.

It might be worth testing.

sylvie369

What you're doing is basically building a rocket launch controller. If you Google that, you should find quite a few examples of circuits. Generally we pass a very low current through the system to light an LED or sound a buzzer to indicate continuity (that is, that there's a current passing through the igniter, or the nichrome wire, in your case) and then using a second switch, pass a high current through to light the thing.

StarMan

Instead of nichrome wire and a match, I have successfully used a 10 ohm, 1/4 watt·resistor connected (with alligator clips) to leads I held against the terminals of a car battery.· It should work well in your circuit.

See attached photo.

Chris I.

SRLM

Is the nichrome wire ruined after a single use? It appears that the resistor is...

Phil Pilgrim (PhiPi)

Resistors are two cents a "pop". I suspect nichrome wire is a tad more expensive. Chris, nice photo, BTW. I've been witness to that very phenomenon — but not intentionally!

-Phil

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'Still some PropSTICK Kit bare PCBs left!

VIRAND

You can recycle Nichrome wire out of old hair dryers and toasters and some kinds of soldering irons.