Any Reason a Minitimer3 Should Work But Minitimer 4 Won't?

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jmmome

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Might just be coincidence, but I now have had two flights with different rockets & different Minitimer 4's where the staging or airstart didn't fire. I had used a Minitimer3 for several staging flights with the one rocket- upgraded to Minitimer4 and staging didn't work. Two weeks ago, tried a dual airstart with a Minitimer4, but it also didn't work.

Does the Minitimer3 send more power to the igniters? I'm baffled. When all is connected, both Minitimer4's seem to be functional when i turn them on. I guess my next step is an override test with the igniter(s) connected (outside the rocket motors, of course:D) to confirm the new Duracell 9V battery gives enough juice to fire the igniter(s). I'm flying both rockets this Saturday, so I'd like to feel confident that I've fixed this.
 

timbucktoo

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Dumb question but is your Minitimer 4 oriented in the "UP" direction?
 

jmmome

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Dumb question but is your Minitimer 4 oriented in the "UP" direction?
Never a dumb question- yes it is. Checks out fine when I turn it on.

I'm in the process of swapping out my Minitimer4's for my old Minitimer3's. I've double-checked the resistance for the igniters, and all looks well with them.

I may fly one of the Minitimer4's at a later date with an igniter on the outside of the rocket, just to see if that Minitimer's G sensor is working properly. If that works, it is simply a coincidence that two Minitimer4's failed to ignite the igniter(s).
 

timbucktoo

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I have never used mine for air start, only for separation charge on motor burnout for 2-stage and it has worked every time. I am using a 2S 180mAh lipo for what it's worth.
 

jmmome

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I may switch to the lipo's as well. I've changed out both back to a Minitimer3. Everything checks out. We'll see how they fly tomorrow. In each case, there is no danger of "augering in", as Stratologgers are controlling the chute deployments.

I REALLY need to use a Minitimer to ignite a separation charge for my two multi-stage rockets. I simply use the ignition of the upper stage to separate them, which is HARD on the booster camcorder looking up.:confused:
 

jmmome

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Single motor on two stage airstart worked- the dual motor airstart didn't on the second rocket. GREAT onboard videos from the two stage rocket- booster & upper stage Mobius camcorders. Drag separation of booster stage about two seconds before upper stage ignited. Stills & video to follow.

Was told that NOT using a LiPo battery for the two motor airstart was my doom. I'll charge up a 2S LiPo tomorrow and replace the 9V with it- test fire the Minitimer with the igniters - outside the G75 reloads- to confirm.

But another beautiful flight of Cinema X-1 even without the dual airstarts working.
 

jmmome

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Like a dope, I used the igniters that came with the G75 reloads- mistake #1. Mistake #2 was that I hooked them together in parallel instead of series.

I need low amp igniters, like Rocketflite provides with their ClusterFire kit, and they need to be hooked together in series- not parallel.

Hopefully, the weather in November will cooperate, I will buy more J800 reloads before then, and three times (third launch for this rocket with airstarts) will be a charm.

FILE0032.JPG
 

mtnmanak

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I have been using 2S LiPo's and they work great, especially with airstarts and/or if you are using WiFi modules from Marsa or Eggtimer (those really suck down the juice), but I have also found that the Energizer 9V Ultimate Lithiums work very well too. You can find them easily in the store and they are expensive for 9V batteries, but cheap compared to LiPos. I have been using them in a lot of rocketry electronics and they haven't failed yet. I find that, out of the package, they crank hot at about 9.8 V and according to Energizer's data sheet, they should push 750 mA continuous for 5 hours at room temp, with a max discharge of 1000 mA. I think this is accurate. I have some of these batteries that have 10-20 launches on them and they are still metering at above 9 V.


I have been running Eggtimers and Marsas with the LiPo on the electronics and using the Lithium 9V for the event igniter/initiator. I am fairly confident that is opposite of conventional wisdom, but it seems to work well, especially for those WiFi modules.

I have also been using the Rocketflite Clusterfire kit pyrogen and wire - awesome. They also have never failed me. I use them for recovery deployment charges as well.

If you put a pyrodex pellet in the top grain of your airstart motors, you can get away with a super low current igniter. Heck, a AA battery and a Clusterfire initiator are supposed to work if you use pyrodex (haven't tried that, but have heard of it being done anecdotally).
 
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