Wheat Bulbs with Raven's and Tele's

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vk2icj
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Wheat Bulbs with Raven's and Tele's

Postby vk2icj » Mon Mar 11, 2013 5:43 pm

Hello all,

I am interested in using wheat bulbs for parachute deployment charges. I have several questions.

1. Does the RAVEN or Tele(metrum mini) altimeters have enough juice to use these?
2. If the above is true can one hook up the bulbs prior to modifying them to the altimeter(s) and see if the altimeter lights them during test modes?
3. If the above both are true can one use/modify the bulbs after testing with the altimeter?

Any help or experience you can share here is appreciated. I am looking at these for parachute deployment not staging btw.

cheers

Chris
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Re: Wheat Bulbs with Raven's and Tele's

Postby OverTheTop » Mon Mar 11, 2013 6:27 pm

What voltage are your wheat bulbs Chris? What are you going to use for batteries for the Raven?

If it weren't so damn hot here in Melbourne today (36deg) I could hook some up to my Raven and let you know. Unfortunately the garage is too hot to work in currently :(. Let me know what you intend using and I should be able to give it a go later in the week.
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Re: Wheat Bulbs with Raven's and Tele's

Postby vk2icj » Mon Mar 11, 2013 6:44 pm

The bulbs are 3 volt wheat bulbs from Whooshtronics. I have never used wheatbulbs before. I haven't sourced a battery yet for the Raven but intend on a Lipo

Chris
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Re: Wheat Bulbs with Raven's and Tele's

Postby OverTheTop » Mon Mar 11, 2013 7:02 pm

The Raven will more than adequately drive the 3v wheat bulbs. I have used the Whooshtronics bulbs successfully for ejection.

If you are using a single LiPo (known as a 1S) you would be able to connect a bulb (still intact, without BP!) to the Raven and it will quite happily light up when activated. If you use a much higher voltage it is likely that the bulb will flash and then burn out because of the excess voltage.

Using a higher voltage than the bulb for ejection is not a problem as it will burn out anyway.

I run a 2S (two cells in series) LiPo for my Raven.

If you are after LiPo batteries, chargers, voltage monitors, JST connectors (don't forget these!) try this site:
http://www.hobbyking.com
If you select the Australian warehouse there is less stock items but the delivery is really quite fast if the items are in stock. Be warned! This site will cause you to spend money!
:lol:
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Re: Wheat Bulbs with Raven's and Tele's

Postby strud » Mon Mar 11, 2013 9:23 pm

Be aware that these bulbs will degrade over time when the filament is exposed to BP.

I assume it is some form of corrosion, whatever it is, after a month or two I definitely recommend measuring their impedance to make sure they haven't gone bad. This has been observed a number of times hence now they are made up not too far off from when they are going to be used.

CS

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Wheat Bulbs with Raven's and Tele's

Postby kopius » Mon Mar 11, 2013 10:48 pm

Two words... Electric Matches!!!
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Re: Wheat Bulbs with Raven's and Tele's

Postby cryoscum » Tue Mar 12, 2013 6:41 am

I've used the wheat bulbs in the past and got a good success rate, i.e. maybe 1 in 20 failures, but the effort making, checking and checking again bugged me. The clincher for me, in terms of logic, was that I cannot see why it makes sense to fly a $150 kit containing $200 of electronics and a $100 reload and then you risk all of it to save $1 on the igniter for the BP.

Troy spoke of trying to get away from consumables altogether and that probably is the right idea. Problem is you have to be Troy to make that work :(
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Re: Wheat Bulbs with Raven's and Tele's

Postby rocket_troy » Tue Mar 12, 2013 10:09 am

cryoscum wrote:Troy spoke of trying to get away from consumables altogether and that probably is the right idea. Problem is you have to be Troy to make that work :(

And 2012 (100% success rate) hasn't changed my mind on that, but you're right- to get a pyroless system that's both reliable and compact, you really need to do your homework and likely have access to a CNC mill.

I will add something to the grain of wheat bulb discussion: I used to also use them, but was (almost) caught out one day when I was using a 12V globe on a 5V supply. Well, it glowed orange-yellow when activated (visible in daylight) and I just assumed that would be plenty of heat to set off BP; it wasn't, not even after a doz tries. Fortunately, I had a backup and saved the rocket, but that was the last time I used them.

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Re: Wheat Bulbs with Raven's and Tele's

Postby rocket_troy » Tue Mar 12, 2013 10:14 am

rocket_troy wrote:...but you're right- to get a pyroless system that's both reliable and compact, you really need to do your homework and likely have access to a CNC mill.


Of course, I would be very very happy for that to be wrong (call it a challenge) :)

Troy
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