Altimeter/Battery help

[chanstevens]

OK, veteran build/flyer who's hitting stupid newbie issues trying to rig a Perfectflite MinialtWD for basic apogee deployment. I've fired two test launches with motor-based backup, and am 0 for 2. First test was probably loose power connection, as it didn't even register an altitude. Second points to a battery problem--recorded altitude fine, but didn't fire the charge. It beeped fine pre-flight signalling adequate voltage and continuity to the drogue charge.

Battery--have to fit in a BT-50, so can''t use a standard 9V. Tried using a fairly fresh N-sized 12v battery (same one used to power the alt15K I've used for years), but it doesn't pass pre-flight voltage check. Perfectflite doesn't recommend these anyway. Switched to stack of (5) 1.5v cells (Energizer 375's) with a lead taped on each end of the stack. VOM meter likes it, pre-flight liked it, igniter didn't like it.

Igniter--home-dipped using 26 gauge shooter wire, 34 gauge nichrome, same basic approach I've used flawlessly with Magnelite's MF dip. For these, though, I'm using a buddy's ematch dip, much hotter/faster burn.

After the failed tests, I tried simply firing the igniter by connecting directly to the battery stack. Nothing. Couldn't light an Estes igniter either. Tried connecting my home-dipped directly to a standard 9v, popped instantly.

Clearly I'm either using a wrong/bad battery or stacking/wiring them wrong. Any tips/suggestions? If there's a single/simple battery I should be going with that will fit in a BT-50, that's my preference.

--Chan Stevens

 

[billspad]

Use one of the new Quest igniters.

 

[madmax]

Sounds like your problem is less battery related and more igniter related. Try using an actual ematch rather than your homemade igniter. MAWDs have a very short latch time on firing the outputs which makes their use with high current devices a problem. Perfectflite corrected this with the HA45K. It has a full second of firing time and it doesn't fire from the capacitor it opens all capacity of the battery up for that second.

I can't comment on the Quest igniters recommended since I have never used them. However, I know that both the HA45K and the MAWD will fire Mtek ematches without any problems.

 

[Zeus-cat]

If you use 357/303 cells you are supposed to use six to power the altimeter. I use the special battery holder sold by Perfectflite as the N cell battery holders at Radio Shack are just a fraction too small for a stack of 6 cells.

I use the X-mas light method for charges and haven't had any problems. I have only flown my MAWD twice so far, but I fired all the charges (1 drogue, 2 main) each time using the stack of six 375 cells.

One trick I learned in ground testing with the X-mas light bulb charge is to pack the powder fairly tightly or they filament won't set off the reaction. If the powder is loose, the filament burns and only smokes the powder. I make the charges per the instructions at Perfectflite and then test them for continuity. I think I have only had 2 rejects (broken filaments) out of 25 I made.

 

[chanstevens]

I'll try a 6-cell stack (rigging electrical tape holder) with a Quest Q2 igniter, maybe even cobble together a Christmas bulb igniter as well. I'd like to go the pure ematch route, but from what I gather they still need an LEUP or at the very least get pretty darned expensive for the batch of dip to get started. Ex--Rocketflite MF-12 and dip runs $50 plus shipping. I know the stuff is goods for hundreds of igniters, but I'm just looking at an application good for a couple of flights, tops.

--Chan Stevens

 

[hardinlw]

You need a low current match or igniter. I used a MAWD at LDRS with some Oxral ematches I had left from the days when you could buy them. I'm down to one and looking for a reliable source of low current ematches.

The Quest Q2G2 igniter is supposedly a low current igniter. I don't know if it's as low as the Oxral, but that's easy to check. If you have access to a digital multimeter, you want a resistance of over 2 ohms (that's what the Oxral is rated).

The other variable is the battery. I was using an alkaline 9v. The internal resistance of the battery determines how much current is can supply and how much the voltage will drop when it tries to fire the igniter. If the battery alone won't fire the igniter, it is unlikely that the altimeter will fire it unless the altimeter is capacitive discharge and has a big capacitor. That suggests that you can screen candidate igniters/matches on the ground by connecting them directly to the battery you will be using. If they don't fire immediately, there is no need to fly them.

 

[falingtrea]

If I remember correctly, a 9V "battery" is just a bundle of 1.5V batteries (maybe AAAA sized?) in series with a shell around it. Have you tried disassembling a 9V battery to see if the parts could be reformed to fit a BT50?

 

[Handeman]

Part of the problem is the home made igniters. You really need to make ematchs. Instead of the the 36 gauge nichrome, use 44 ga. It's much smaller and you might need one of those lights with the magnifier in the center, but wrap the nichrome with as small of bridge between shooter wires as possible, 1/16" is good.

As for a dip, you can make your own. Make up some NC lacquer (3 ping pong balls in 4 oz acetone) Mix in ground BP or Pyrodex to make your dip. You only need a little bit on the bridge and it will light your charges. These may not work for other things as well as commercial ematchs, but for ejection charges with low current electronics the will work quite well. In fact, if you're using FFFFg BP for your ejection charges, you may not need to dip them at all, just make sure a few grains are in contact with the bridge wire.

Use the altimeter and battery in a vacuum chamber to ground test the ematchs. Ground test, ground test, and ground test.

 

[JimmyL]

I have used the E-matches from Quickburst. The kit does not require an LEUP. So far, every one I have tried has fired. These E-matches use 50ga nichrome and a simple pyrogen. You can ground test easily with a computer connected to the MAWD. If you want to make a large quantity of (100) E-matches, you can order the blanks from ODA enterprises. I think one hundred match heads with nichrome already soldered on cost about $12 plus shipping and for the pyrogen you can order enough of the two components for about $15 plus shipping. You can use Cat 5 wire and you end up with E-matches for about 40 cents each. You can also order shooters wire from Seminole wire if you want them to look like the commercial made ones. Hope this helps. Here is the url for ODA.

https://www.oda-ent.com/default.htm

 

[quickburst]

I'll try a 6-cell stack (rigging electrical tape holder) with a Quest Q2 igniter, maybe even cobble together a Christmas bulb igniter as well. I'd like to go the pure ematch route, but from what I gather they still need an LEUP or at the very least get pretty darned expensive for the batch of dip to get started. Ex--Rocketflite MF-12 and dip runs $50 plus shipping. I know the stuff is goods for hundreds of igniters, but I'm just looking at an application good for a couple of flights, tops.

--Chan Stevens

20 matches, less than $50.00. Plenty of material left over to dip more, all you have to do is buy more heads.

E-Match Kit: https://www.quickburst.net/e_matchkit.htm

E-Match Blanks: https://www.quickburst.net/ematch_blanks.htm

Have a permit, or a buddy that does? Buy real e-matches see: https://www.quickburst.net/q_match.htm

questions?

 

[ttabbal]

I've used the Quickburst e-match kit. It works great. Easy to use, haven't had a misfire yet.

 

[bobkrech]

Chan

The problem is you igniters, not the batteries. The MAWD has a CD pyro circuit that stores and discharges 0.19 Joules in a capacitor that is active for 50 milliseconds. It is designed to fire only low power e-matches. It will definitely not fire you home-brew igniters because the bridge wire is too large a gauge and requires more energy than the circuit can deliver.

The MAWD will fire commercial low current e-matches, the Quickbust e-match kits, the new low current Quest igniters, and the N3 hot wire canister.

Bob

 

[chanstevens]

Chan

The problem is you igniters, not the batteries. The MAWD has a CD pyro circuit that stores and discharges 0.19 Joules in a capacitor that is active for 50 milliseconds. It is designed to fire only low power e-matches. It will definitely not fire you home-brew igniters because the bridge wire is too large a gauge and requires more energy than the circuit can deliver.

The MAWD will fire commercial low current e-matches, the Quickbust e-match kits, the new low current Quest igniters, and the N3 hot wire canister.

Bob

Thanks. Not having an LEUP and not wanting to spring for $50 for a kit, I did manage to bench test successfully on a Quest Q2. I also picked up some xmas bulbs to mess around with. I guess I have a lot to learn about ematches versus regular igniters. I really thought I was getting close enough to ematch with my 26 gauge shooter wire, 36 gauge nichrome bridge, and a pretty hot dip from a buddy who air starts HPR with it all the time. It seems 36 guage nichrome is too heavy for ematch.

 

[DAllen]

Buy e-matches at the launch and use the xmas bulbs for ground testing. That way you are technically operating under the LEUP of the seller just like when we used to have to buy motors that way prior to the ATF court win.

I've done a lot of xmas bulb ground testing and find them to be somewhat reliable. Those filaments are soooo delicate I just don't trust them that much. I figure about a 1 in 4 failure rate. Maybe its the way I prep them. :confused2: If I use xmas bulbs on a flight I double them up on each charge.

-DAllen

 

[jcsalem]

I love the MAWD and find it very reliable.
bobkrech gives an accurate summary of compatible igniters.

I started with Xmas lights because no LEUP was required but they have several problems:
1) The sockets corrode easily. I was often needing to sand the contacts.
2) Xmas bulb charges are very fragile. Dropping one on concrete could be enough to break it.
3) They took too much time to prepare.
I had an 80%-90% success rate with the bulbs but I'm looking for better.

I've pretty much settled on the Newton's 3rd hot wire canisters. I've had only one failure in two dozen launches with them (which was preventable).
The canisters have graduated markings which are very helpful for consistency.

Jim

 

[Handeman]

I love the MAWD and find it very reliable.
bobkrech gives an accurate summary of compatible igniters.

I started with Xmas lights because no LEUP was required but they have several problems:
1) The sockets corrode easily. I was often needing to sand the contacts.
2) Xmas bulb charges are very fragile. Dropping one on concrete could be enough to break it.
3) They took too much time to prepare.
I had an 80%-90% success rate with the bulbs but I'm looking for better.

I've pretty much settled on the Newton's 3rd hot wire canisters. I've had only one failure in two dozen launches with them (which was preventable).
The canisters have graduated markings which are very helpful for consistency.

Jim

I agree that the xmas bulbs can be problematic, but they can be reliable. I've used them on 10 DD flights, 20 charges, [cross fingers, knock on wood] and never had a failure.[/cross fingers, knock on wood]

1. I never use the sockets.
2. I pull the wire wrapped around the filament posts out so I get a true continuity reading on just the filament.
3. I always use two bulbs in parallel.
4. I solder the lead wire to the two bulbs.
5. I use hot glue to glue the two bulbs into a wrap of paper and seal the end.
6. I make the paper tube/bulb assemblies at home, never at the launch site.

With that said, I've been experimenting with making my own ematches with 44 ga. nichrome wire. That has worked very well with my HiAlt45. They didn't work near as consistently with a MAWD.

Although I haven't had a failure with the xmas bulbs, I feel the ematches would be even more dependable.