Continuity tester

[Updup]

Is it possible to check coninuity without lighting a small bulb? And how do the firing systems that use normal E-matches do it? My guess is the matchs fire on say 100 mah and up, but it tests on 50 mah? <(Just an example, they may or may not fire on 100mah)

 

I'm thinking about wiring speaker jacks to this device http://cgi.ebay.com/...=item3efd5f0cea And adding a continuity tester... obviously this could work without the tester.

 

I'm not sure if you guys think that the frequency on this is too broadly used and not safe for a firing system or not, but if you have any concerns regarding this please tell me . And it claims 3000ft! Dang!

 

 

 

http://www.goodluckbuy.com/images/detailed_images/image/s12c-dc12-2.jpg

Edited September 23, 2010 by Updup

[Arthur]

DIY fuseheads are a totally variable resistance, and firing current, however professional igniters usually TEST at well less than 20mA possibly in the region of 5mA for preference. A pro igniter will typically fire at 500mA but account for needing an amp to make them all fire and on time.

[Updup]

DIY fuseheads are a totally variable resistance, and firing current, however professional igniters usually TEST at well less than 20mA possibly in the region of 5mA for preference. A pro igniter will typically fire at 500mA but account for needing an amp to make them all fire and on time.

 

So, what your saying is, they send a very low current through professional igniters for the continuity check. But X-mas light igniters are just too unpredictable to acually get a current low enough to test continuity without any chance of unintended ignition? Ahh well, any other features I could add to this DIY firing system?

[Arthur]

A proper Blaster's Safety Ohm Meter reads 0 - 200 ohms and is the best method for checking continuity, However at £200+ each they are costly and fragile.

You should be able to determine the intended resistance of each circuit and check for that value +/- say 5%.

 

Yes Updup because DIY igs are so variable there are no fixed values to work from. However WITH DUE CARE you could simply try to use a cheap economy multimeter set to an ohms scale, and test at a place and distance where inadvertent ignition would not be a problem. Conduct tests before coming to a conclusion. However in professional fireworks, prox FX and HE work in the UK it's considered that all tests should be done from a place of safety lest the charge should fire.

[Updup]

Yeah, I think I'll leave the continuity tester out of my project... Thats a little too much fr me. Thanks for the help! And do you think the pictured item above will work?

[Richtee]

A proper Blaster's Safety Ohm Meter reads 0 - 200 ohms and is the best method for checking continuity, However at £200+ each they are costly and fragile.

You should be able to determine the intended resistance of each circuit and check for that value +/- say 5%.

Seems to me the old Wheatstone Bridge circuit can be run VERY low current and is quite sensitive. I have never used electric igniters and have no experience- that just popped into my head from my electronics background.

[Peret]

Seems to me the old Wheatstone Bridge circuit can be run VERY low current and is quite sensitive. I have never used electric igniters and have no experience- that just popped into my head from my electronics background.

Right. A 20mA test current is what you needed to light a small bulb - 1930s technology. 5mA will light an LED - 1970s technology. The Blaster's Safety galvanometer does it with 50 microamps, but that's - um - 1890s technology. These days, it's perfectly feasible to have a 5 microamp continuity detector permanently hooked up on each line for a per-line cost of about 25 cents.

[patsroom]

So, what your saying is, they send a very low current through professional igniters for the continuity check. But X-mas light igniters are just too unpredictable to acually get a current low enough to test continuity without any chance of unintended ignition? Ahh well, any other features I could add to this DIY firing system?

 

 

I have fired alot of X-mas bulb igniters using LED lights for the continuity test of the igniters. Never have I ever had a prefire from the test lights as the amps and volts were well within the safety limits of my DIY system I used. I am now in the process of build a firing system with 120 cues total using the same concept.

[patsroom]

I think this well do it

 

 

wrong download see next post

thank you

Switch and or test.bmp

Edited September 24, 2010 by patsroom

[patsroom]

I think this well do it

 

That's a poor picture. Let's hope this one is better

Switch and or test.bmp

Edited September 24, 2010 by patsroom

[Miech]

I think it would be better to use a constant-current supply rather than putting the LED's direct to the battery. Even better would be to use a constant current supply in combination with a comparator. This decouples the LED from the firing circuit, bringing the current back to below 1mA, as the comparator is a voltage driven device. I got a nice schematic for it *somewhere* on my pc, as wel as a PCB design for it. If I find it back I'll post it here.

[Updup]

That's a poor picture. Let's hope this one is better

 

Hmm, that seems too simple... Does it work for you? and on what voltege are you runing your system on?

 

Mabye I could hook up my test/fire switch to the ground on all my lines, plus my resistor and LED, I can make it work where you flip an "On" switch somwhere, and than flip another switch to test, then run through on the remote pressing 1-12, and if there is continuity on the cue that your pressing the led turns on.

 

What resistor do you suppose I'll need? Hang on... How does your LED still light up? Wouldn't the current required NOT to fire the X-ms light be way less then that required my the LED? So, Miech, you said somthing about removing the LED from the direct loop, so the comparator is like a voltege sensor? How might that work?

 

 

Thoughts?

[patsroom]

Yes the system works for me. As to the volts that I have used it was a 12 volt car battery.

The resistor used depends on the LED and the voltage that you are using. I see no reasons that a higher voltages of 48 or more can not be used as the firing volts as long as the resistor is designed for that high.

Your testing curcuit is left well under the firing amps of the igniter, as long as the switch is not closed the circuit run through the LED. This will keep the LED lite as long as the ciruit is in a closed loop with the igniter or a wire in its place. When the firing switch is closed the LED is by passed and the full firing circuit is released to the igniter causing it to fire.

 

Looking the design over....The relays would be used as the switch in the circuit. This would means that you would need 12 LEDs and 12 Resistors.

Edited September 24, 2010 by patsroom

[patsroom]

http://www.robotroom.com/Launch-Controller/Schematic-of-a-simple-rocket-launch-controller.gif

Schematic of a simple rocket launch controller.

 

Found this on the net shows the design of a simple controller

 

 

[Updup]

Looking the design over....The relays would be used as the switch in the circuit. This would means that you would need 12 LEDs and 12 Resistors.

 

Thanks for the insight! I'm accually only going to need 1 LED and 1 resistor, because i'm going to be adding the test circuit on the line coming back to the device... Plus, I think i'm going to use a little buzzer I have, and not an LED, or mabye both.

 

Just orderd the main module a few minutes ago, on ebay they sell it for $32 + Free shipping, the same company however sells it for $19 + free shipping on thier website!

 

I'll make a topic or guide on how to make this... so stay tuned [=

 

Also, I did a quick test and found out that a AA won't heat an X-mas light, so that clears alot up for me. I got a device that holds 8 AA's and has a plug in for a 9v battery connecter, (and 8 AA = 12V) so that what I'll use for the field module, and then the E-matches I'll shoot with a 9v so that its nice and compact, although I might throw in another AA to power my continuity check circuit without a resistor.

[Miech]

I couldn't find the original file, so I drew a new one.

 

LowCurrentTest.pdf

 

R1 and R2 are a voltage divider, dividing the supply voltage by 2 (if R1 and R2 are equal) providing a reference voltage for the comparator. R3 and R4 are a voltage divider too, where R3 has a bigger resistance than R4 and the igniter combined. The total resistance of R3, R4 and the igniter should be high enough that the current through the igniter is about 1mA or so. R3 also serves as drain for residual voltage if the igniter would be disconnedted or fired. IC1A is the comparator, if the voltage on the + input exeeds the voltage on the - input, the output will be high (almost supply voltage). R5 limits the current through the LED. Decoupling the V+ above R4 will turn off the LED and stop any current from flowing through the firing circuit.

 

The LM324 is a quad opamp, so you can test 4 circuits using just one opamp. Please use a socket for mounting it on a PCB, they're easy to fry.

 

The exact values needed for the resistors need a little experimentation. For a 12 volt system, assuming a 1000 ohm igniter, the following values would be a good starting point:

 

R1,2: 10k

R3: 5k1

R4: 4k7

R5: 680 ohm (assuming 20mA LED)

[Updup]

Hehe, at this point, I'm going with the simple route [= thanks for all the info though!

[Miech]

I found the original files back, including the PCB design. It uses a red/green dual LED with common cathode. When red, the igniter has been fired or isn't working properly. When green, the igniter is conducting. Probably way too fancy for most of us, but heck it looks cool.

 

Schematic.pdf

Silkscreen.pdf

Transfer.pdf

 

I later added a 10k resistor between pin 3 of the opamp and the V+ connection. This prevents your opamp from hitting the rails, prolonging its life expectance significantly.

 

For members knowing how to use Cadsoft Eagle, I got the files attached below.

 

FiringBox_.zip

[Updup]

Ooh! Thats a great board layout you have there! The R/G LED is a cool idea too, helpful to determine if its your match thats messed up or your box.

 

Can't wait until my RF wireless box gets here, and it should come right when I get back from my friends farm [=

[al93535]

Why not just break open 10 light bulbs, fill them with black powder and use a multimeter to test them with? If they don't fire then you are good.

[Miech]

It's just not fancy enough if there are no LED's involved .

 

No but serious, if you want to shoot 100+ things you don't want to measure each bulb with a multi meter.

[Aquarius]

Most X-mas lightbulbs have a few turns of thin wire connected to insure that if one pops, the whole chain won't go dark. You will measure the electronflow through the "fail-safe"wire instead of the ignition filament and have a false reading of current.

[Updup]

Why not just break open 10 light bulbs, fill them with black powder and use a multimeter to test them with? If they don't fire then you are good.

 

Yeah I tried it without filling bulbs, but the filament didnt get hot... So I'm good, this was with a simple AA.

[patsroom]

Most X-mas lightbulbs have a few turns of thin wire connected to insure that if one pops, the whole chain won't go dark. You will measure the electronflow through the "fail-safe"wire instead of the ignition filament and have a false reading of current.

 

http://tlc.howstuffworks.com/family/christmas-lights1.htm

 

http://static.howstuffworks.com/gif/clights-shunt.jpg

Today's standard mini-light bulbs contain a shunt wire below the filament. If the filament burns out, the shunt activates and keeps current running through the bulb so that the rest of the strand stays lit.

 

 

Well I must say, "That's a good call".

 

But if this shunt is not activated, it should not interfer with what we are doing.

 

There might be a chance that you could burn through the oxide and make the final connection of the shunt. But I think that we push the voltage at a lower requirement and for a very short time that the shunt lacks the current needed for the connection to by pass the destroyed filament.

 

Any thought about this would be nice.

 

[Updup]

Yes, pretty much all lights have this, and its the main reason why a continuity tester on them turns out to be really easy, since that pulls some of the current, increaseing the amout of current needed to heat the filament to a point where the BP lights.

 

I don't see any problems with thier being that extra twist of wire at the base, maybe if you did a continuity check after the show to find duds, it would say it was still letting current past (It is), so that could be a problem if that bugs you...