MJG/Electricmatch starters

[Joshua F Thomas]

So I ordered some blackpowder and composite starters from https://electricmatch.com/rocketry

Anyone have experience using this vendor? The prices were low enough ($0.69 for the BP starters) that I might order large quantities if they work out well. Having long wires will make clustering much easier.

 

[neil_w]

Please report on your experience with them, particularly with clustering.

 

[JDcluster]

I use them for ejection charges. They don't require a permit. I use the cheap Chinese orange wire for clustering motor starters. They burn a little longer rather than pop. I still dip the Orange wired things.

 

[Joshua F Thomas]

So these came today....




The BP igniters are 12 cm long. The composite igniters are 22 cm long.

I did the a bench test of one BP igniter on my 12V controller. The results are .... energetic.

 

[Joshua F Thomas]

First issue encountered: The composite igniters will not fit inside the Quest Q-Jet 18mm motors. Might be ok for larger composite motors.

 

[neil_w]

That’s not altogether surprising, the Qjet nozzles are really small. Did the company really recommend the composite igniters for the Qjets?

 

[Joshua F Thomas]

Not directly, they’re just listed as “composite igniters”. That’s kind of a broad category, honestly....

 

[Joshua F Thomas]

Actually, I take that back. They list them specifically for Aerotech motors. So that’s my bad.

I’ll have to ask if they have any igniters compatible with the Q-Jets

 

[rharshberger]

Actually, I take that back. They list them specifically for Aerotech motors. So that’s my bad.

I’ll have to ask if they have any igniters compatible with the Q-Jets

Odds are those igniters also will not fit Aerotech 18/20 reloadable motor nozzles, and some of the small throat AT 24/40 nozzles.

 

[Joshua F Thomas]

Hmm.
I double checked my invoice. I had ordered the Red Hot minis but they do not look like the ones on the page. I’m going to have to email then to see if I got the right product.

The BP ones look correct, however.

 

[cwbullet]

Hmm.
I double checked my invoice. I had ordered the Red Hot minis but they do not look like the ones on the page. I’m going to have to email then to see if I got the right product.

The BP ones look correct, however.

Keep us updated.

 

[Joshua F Thomas]

Vendor wasn't able to determine what my composite igniters were from pictures, gonna keep working on it.

Black powder igniter report:

1) Single motor C6-5: success
2) Three motor B6-4: two ignited. the third failed because of my own wiring fault, not the fault of the igniter.

So far, so good. If I get a few more fully successful clusters, I'm going to by like 100 pack of these.

 

[Joshua F Thomas]

I bench tested one of the black-powder igniters today for minimum current. My constant-current power supply is set for 12 V and I increase the current until ignition occurs. 18g wire of about 12" is used between the igniters and power supply.

Resistance testing on my remaining BP igniters gave these resistance values in ohms: 10, 11, 18, 20, 24, 36, 38, 48, 53

This is a pretty wide range of resistance, so people using these for clusters should consider testing their igniters ahead of time and using those that have the nearest set of resistances.

I used the worst case igniter, the 53 ohm one in my remaining group. The igniter did not trigger until 1.250A of attempted current.

I'll do some tests on my composite igniters next.

 

[Joshua F Thomas]

Composite 'Red Hot Mini' igniter tests.

Resistance in ohms: 83, 95, 107, 128, 146, 206

The 206 ohm igniter failed after a few seconds of 100 mA of current; it dropped down to 20 mA. It did not flame or burn, and a continuity test showed over 6k ohm of resistance.

I followed up with some longer-time current duration tests on the 128 ohm igniter. It did not fire or fail after 30 seconds of 50 mA, 100 mA, and 150 mA. This should be good for continuity. At 250 mA it started to smoke. I switched up to 1 A and it immediately burst into several seconds of flame.

146 ohm igniter: 30 seconds at 50 mA. Rapid fail w/o ignition at 100 mA.

107 ohm igniter: 30 seconds at 50, 60, 70, 80, 90 and 100 mA. I wanted to see how fast ignition would happen and how energetic the event was, for high amps, so I then fired it at 3 amps. Instant flame, which lasted about two seconds.

The smell of these burning is oddly pleasant. Must be some chemical which smells nice.

Conclusions: Use < 50 mA for continuity tests. 20 mA is probably better. High resistances mean you want to use a high-amperage delivery system.

 

[neil_w]

Wait, did you mean to say milliohms? I'm trying to visualize how you're driving 3A across a 107 ohm igniter.

Unless my brain is broken this morning.

 

[Joshua F Thomas]

No, these are all in ohms. The constant-current power supply will try to push that much current through the igniter. I assume the igniter breaks down before it actually hits that much current. "3 A" is closer to "just hit it with all you can".

 

[FredA]

The constant-current power supply

That PS will run out of headroom at some point.
To push 3A through a 107-Ohm resistor, you need 321 volts.
Seriously doubt your supply will do that.

 

[neil_w]

OK, so I'm looking at your numbers there. 146 ohm igniter fails without lighting at 100 mA, that' still over 14V. Using a standard 12V launch system, that's a fail, right? Those would need to fire at 50 mA or so in order to work reliably with a 12V system. Still trying to understand how these are supposed to be used.

 

[Joshua F Thomas]

Good question! I honestly am not sure.

I double and triple checked my resistance readings, and a reference resistor. The readings are correct. I'm suspect the resistance might be changing in the presence of current, or that thermal changes are causing resistance drops. I can't get a resistance reading while current is also flowing, so I'm not quite sure what to make of it.

Edit: Actually, it occurs to me I can see the real-time voltage and current and derive the resistance from it; let me do that and see what happens.

 

[Joshua F Thomas]

Oh yeah, it's clear the resistance changes as soon as you drive any current through these.

Initial reading:




40 mA gives 2.20 volts; that's 55 ohms.





50 mA gives 2.40 volts; 48 ohms.





60 mA, 2.76 v; 46 ohms.



3 volts at 70 mA; 42 ohms.





Retesting resistance with power off after have driven 70 mA for 10 seconds or so:




Jumping up to 500 mA causes it to smoke and flame fairly quickly, and tops out at 4.91 volts, or 9.82 ohms.

 

[Joshua F Thomas]

A take away here is that if you can drive 500 mA at 6 volts instantly, you will probably ignite these, at least from testing so far. The internal resistance also seems to keep lowering as you drive more current, and that makes me wonder what the long term effect is with a continuity test, or if it degrades the igniter any.

A lot of equipment uses an always-on continuity test. If you push 50 mA through this for 5 minutes while other launches on your club pad are happening, will it eventually degrade enough to fail? Maybe I should do that test.

 

[Joshua F Thomas]

10 minutes of testing later, and my last composite igniter:

Initial resistance: 96 ohm. 50mA constant current.

Start: 2.36v
30 s: 2.13 v
60 s: 2.07 v
90 s: 2.03 v
2 m: 2.00 v
3 m: 1.98 v
4 m: 1.94 v
5 m: 1.93 v
6 m: 1.91v
7 m: 1.89 v
8 m: 1.88 v
9 m: 1.87 v
10 m: 1.86v

After this 10 minutes, I bumped it to "take all the power you want" and it immediately flamed as before, so the 10 minutes @ 50 mA hadn't prevented it from working.

I'm speculating that the low level of current is slowly causing the igniter material to react, hence the gradual drop of voltage as the pyrogen either heats up and becomes more conductive or is reacting into something more conductive. On the positive side, even 10 minutes at 50 mA continuity doesn't seem to cause it to stop being useful.

 

[neil_w]

Very very interesting testing. It sounds like lower continuity currents might be desirable but not essential.

If you're ever interested in going back to the BP igniters, it would be interesting to hear how they do with weaker controllers, e.g. 4xAA or 1x9V. Clearly they should be good for 12V club launch systems.

Also, although you said it would be good to group igniters with like resistance for clustering, I'm not sure there's evidence for that yet. With 12V applied, they might all light at pretty much the same time. Might need some high-speed photography to verify (even 240 fps smartphone video should be enough).

Thanks for doing this, I'm enjoying watching from the sidelines.

 

[Joshua F Thomas]

Very very interesting testing. It sounds like lower continuity currents might be desirable but not essential.

If you're ever interested in going back to the BP igniters, it would be interesting to hear how they do with weaker controllers, e.g. 4xAA or 1x9V. Clearly they should be good for 12V club launch systems.

Also, although you said it would be good to group igniters with like resistance for clustering, I'm not sure there's evidence for that yet. With 12V applied, they might all light at pretty much the same time. Might need some high-speed photography to verify (even 240 fps smartphone video should be enough).

Thanks for doing this, I'm enjoying watching from the sidelines.

I have one of the Estes 4xAA igniters, so that should be easy enough to test. I will also be reordering the BP igniters as they've worked well for me so far and 12" leads make cluster wiring so much easier.

I don't think it can hurt, and might help, to match like resistances on the igniters. Clustering is already enough of a challenge that getting out the multimeter to check through a few igniters is not a ton of extra work.

 

[manixFan]

Hmm, it sounds like conductive pyrogen. So as you drive more current it bridges across the conductive fibers. It would also explain why it changes over time. I use the low voltage stuff for making mini-composite ignitors that will fit into 18mm AT motors.

Odds are those igniters also will not fit Aerotech 18/20 reloadable motor nozzles, and some of the small throat AT 24/40 nozzles.

Recall that AT has you build some of those motors with the ignitor in place, since even their ignitors won't fit through the nozzle. Unless you mean the wires are too big to fit through the nozzle. They are a bear to work with once built.


Tony

 

[Rocketjunkie]

I talked with Jeff @ electricmatch.com when the first BP starters came out. There may have been changes since then. However, they used a conductive pyrogen and the resistance varied a lot. Do not attempt to use these in clusters. He would not give no fire and all fire currents. Note that all starters are current driven devices. All you need is enough volts to drive the all fire current through the resistance. I do not know about the composite motor starters.
For reliable 24 mm cluster ignition use FireWire starters. Stick them in as far as they will go and tape over the nozzle to hold them in. They do not have to touch the propellant although I check in the nozzle and make sure I can see BP and no clay over it. I have not tried to light 18 mm motors this way.
I have dealt with MJG for many years with no problems. Parcel post shipping may be a problem (you will eventually get the package) as the postal service is already suffering slowdowns due to Trump's crony (Louis Dejoy) has already been tampering with service.

 

[Dugway]

I have used the MJG BP Rocket Starters in clusters to launch my Cluster Ducks (7 x black powder motors) a dozen or so times. Every motor has ignited every time AFTER I quit trying to chain them up and just wired them in parallel as suggested by the manufacturer. I also use a relay activated LiPo cluster boost box, so I'm sure that helps. These guys have been supplying electric matches to the pyrotechnic community for decades, follow their recommendations and you'll be fine.

 

[Joshua F Thomas]

I have used the MJG BP Rocket Starters in clusters to launch my Cluster Ducks (7 x black powder motors) a dozen or so times. Every motor has ignited every time AFTER I quit trying to chain them up and just wired them in parallel as suggested by the manufacturer. I also use a relay activated LiPo cluster boost box, so I'm sure that helps. These guys have been supplying electric matches to the pyrotechnic community for decades, follow their recommendations and you'll be fine.

Did you mean to say parallel? Or did you mean to say serial?

Cluster igniters should *always* be wired in parallel. I can't think of any reason you'd ever want to wire them serially.

 

[prfesser]

Did you mean to say parallel? Or did you mean to say serial?

Cluster igniters should *always* be wired in parallel. I can't think of any reason you'd ever want to wire them serially.

Actually, electric matches (the regulated ones; I dunno about others) are *always* wired in series in fireworks use. At 1.5 v per match, a 12v car battery will handle eight matches without needing anything more than 22 or 24 ga lead wires. The action time is so short that they will pop together, virtually every time. When I've done small electrically-fired shows I wire the matches in series.

Higher-current matches, and most motor starters used in rocketry, are wired in parallel, of course.

Best -- Terry

 

[Joshua F Thomas]

Indeed, that's why I asked. The rocket igniters should be wired in parallel; they're not the same as the igniters used for fireworks.

On a more practical note, if your series igniter fails for a firework the firework just doesn't go off; fail is safe. If one of your rocket igniters does not ignite, the rocket can launch with under-powered motors, and that *is* a safety problem! Parallel igniters on a rocket aren't just good wiring practice, they're a safety feature.