21 replies to this topic

[HerbertMunch]

Im trying to make a detonator out of a disposable camera.

Ive got it all wired up ok, but when i attach the unit to a long wire (cat5 pair) 5m, and press the fire button, A spark occurs at the button, and the ematch does not fire.

If I attach the ematch without the long wire, the ematch fires perfectly.

I have wired the capacitor up to the fire button and the output terminals, Is this right?

Does any one have an ideas?

thanks very much

[Caramanos2000]

First I dont think you need 300v to fire an ematch, I do it with 18v. Anyways no, dont hook up to the capacitor. Hook up to the two wires that were attached to the flash, the blue and red, not the white. Then interupt one of the wires with your fire switch, should be good to go.

[BrightStar]

Anyways no, dont hook up to the capacitor. Hook up to the two wires that were attached to the flash, the blue and red, not the white. Then interupt one of the wires with your fire switch, should be good to go.

In most cases, hooking up to the flash tube is the same as hooking up to the capacitor...

HerbertMunch, we'll need some numbers to help you here... the energy stored in the capacitor (0.5 * capacitance * voltage squared) will be split four ways in direct proportion to the resistance of each element of the series loop - the ESR of the cap (i'd guess about 5 to 10 ohms), the switching loss (not much), the resistance of the cable (15 ohms per 100m of bell wire), the resistance of the match (2 ohms for a commercial match).

You only need to deliver approx 0.3 joules to a commercial e-match to pop it reliably. If you're using a hefty length of nichrome it will need much more. Send us some measurements and we'll do our best

Edited by BrightStar, 15 May 2007 - 02:31 AM.

[HerbertMunch]

In most cases, hooking up to the flash tube is the same as hooking up to the capacitor...

HerbertMunch, we'll need some numbers to help you here... the energy stored in the capacitor (0.5 * capacitance * voltage squared) will be split four ways in direct proportion to the resistance of each element of the series loop - the ESR of the cap (i'd guess about 5 to 10 ohms), the switching loss (not much), the resistance of the cable (17 ohms per 100m of bell wire), the resistance of the match (2 ohms for a commercial match).

You only need to deliver approx 0.3 joules to a commercial e-match to pop it reliably. If you're using a hefty length of nichrome it will need much more. Send us some measurements and we'll do our best

Thanks, but ive discovered that the camera flash works a treat with a thick wire.

Edited by HerbertMunch, 14 May 2007 - 09:21 PM.

[dr thrust]

is that what i need then! commercial e match, my slr flash wont fire nichrome but its good at fuseing my switches together!!

[HerbertMunch]

Im just using DIY matches, and a modified disposable camera.

The matches are just a bit of 2 core mains wire with a bit of the thick outer insulation cut off.
I then remove the ends of the insulation from the two insulated inner cores, and then simply rap nichrome around the first inner wire a few times, and then the other one a few times (only one strand of nichrome connecting between the two copper cores).

I dont even bother with trying to solder it on, instead I apply and ultra thin layer of NC, let it dry for about 30 seconds, and then sprinkle fine black powder over it.

Ive put the camera up inside a tupperware container, with buttons and switches (charge,fire,cancel, etc)
Ive rigged the fire button up to the Large capacitor (300v) in series with the on position of the on/off switch, for safety reasons)

when i use the modified disposable camera with my diy matches, the nichrome wire pops and breaks, with a massive spark.
This seems to do the trick most of time, 85% success so far. Im still perfecting this though.

[HerbertMunch]

my slr flash wont fire nichrome but its good at fuseing my switches together!!

I dont quite know what you mean by sir flash, but if you are talking about using high voltages to detonate, you must be sure that the terminals of the buttons are well insulated (if close together), and also that they are rated for the voltage that you intend to switch.

[Asteroid]

I tink your problem may be that you're using mains wire, which is intended to not heat up with currents up to 13A. Try using strands of steel wool, audio wire, or just thin ni-chrome

[rocket]

I think its not sir flash but SLR flash (SLR= Single-Lens Reflex)

[dr thrust]

hi whats the swg of your nichrome mines 28 any good?

[HerbertMunch]

I think its not sir flash but SLR flash (SLR= Single-Lens Reflex)

oh, so it is.
Silly me.

[dr thrust]

I tink your problem may be that you're using mains wire, which is intended to not heat up with currents up to 13A. Try using strands of steel wool, audio wire, or just thin ni-chrome

thanks i see the prob now, firstly i started off with mains wire,and had too pop it with a car batt,then after joining this forum i found out about nichrome, went and got myself some 28 swg,but no bannana, so ive ordered some 33 and 44, never mind i could use the 28 swg for clothes hangers , car aerials ,about my switches going to try a relay to switch the power,got a few kicking about and it makes the fireing panel look a bit more interesting also i put a meter across the cap its storeing 125v but the caps rated at 330, are they rated double the volts as a safty feature?

[Asteroid]

I dont think it'd make a good aerial due to its high resistance, but i might be wrong. It's low voltage could be due to you charging it with the wrong voltage or something

[dr thrust]

I dont think it'd make a good aerial due to its high resistance, but i might be wrong.

sorry just my silly sense of humour ive got a full roll of the dam stuff!! ive got the 33 swg nichrome now and its much better and has fired some visco from 30 ft with the flash unit two out of 5 times which is much better than nothing could do with some 35-40 where can i buy?

[Asteroid]

Ebay has this which is approx 38swg from an online conversion chart. I can also personally reccomend the seller, who I bought some polymorph plastic from about a month ago.
Also try speaker wire which is made from loads of tiny strands of copper, check it's the right stuff first though.