Flashbulbs, Christmas Lights, and Glow Plugs

[Rock_It]

.

 

[Chrisn2]

If you used the altimeters output to trigger a sub-circuit that runs on a higher voltage to light the flash bulbs it can be done in a "chrisn2 theory"

Flash bulbs will be classed as 1.1 c explosive by the ATF soon

(they better not otherwise we will have to prove there tactics wrong on something else, pehaps a ultra light APCP).
I can help you by perhaps makeing a website/forum dedicated to proveing the ATF are a step behind us in this war.(argh dontlisten just another general rant of mine i cant help it.) :kill:

 

[Johnnie]

Flashbulbs have been around for a long time. I believe that a small company made holders for flashbulb ejection charges...Robbies Rocketry or something like that.

Christmas tree bulbs have limited success, in that they are somewhat cumbersome to make. Jimmy Yawn's website chronicals his method for this type of e-match...

Homework and ground testing is a must here when concidering these forms of recovery.

good luck!

Johnnie

 

[WillMarchant]

Originally posted by Rock_It
...
Also, I know about the EFC, but what I am looking for is for DD vehicles. The EFC will only work for single deploy. Most of the rockets I build will be DD in the future as far as my HPR stuff. Probably all of my HPR stuff will be DD.

Thanks for taking the time to read this. I'm hoping this thread will be productive and will help alot of people in need.

You could use two EFCs and do dual-deploy: just set different delays.

 

[jderimig]

I think the future is in CD spark. The advantage here is since they are not consumed you can repeatably fire them until the ejection charge is ignited. Could be very, very reliable.

Cheap prototypes exist in single-use cameras....

 

[r3tic]

Something I have recently come across is using resistors as e matches. This article covers most of what you need to know.

https://www.aeroconsystems.com/tips/dahlquist_resistor_igniter/dahlquist_igniter1.htm

 

[Rock_It]

.

 

[bobkrech]

Rock_It

The late Bob Dahlquist was a very talanted rocketeer and wrote many excellent technical papers on rocketry. The resistor method he proposed was specifically for launchers, not altimeters. The rocket altimeter pyro circuits are low voltage, high current supplies, not the high voltage capacitive discharge systems Bob described in his paper. This is not a relevant method for BP ejection charge ignition.

A high voltage capacitive discharge method, basically the same as above but with a spark plug instead of the resistor, will work if you want to custom design a multi-kilovolt electronics package, but why. It offers no advantage over proven existing methods so why do it.

The use of flash bulbs or christmas tree bulbs are simple, proven existing methods of BP ignition. When done properly they are 100% effective.

Recently AT has developed a clever reusable glow plug BP igniton system that is 100% effective when used as directed. A BP canister system employing a glow plug ignitor will work fine with any altimeter capable of delivering 2+ amps for 1 second. This is a bit different from altimeters that draw current from a capacitor to actuate an e-match. E-matches have low thermal mass and actuate in a few milleseconds so the capacitor does not have to be very large. A glow plug has a lot of mass and will take anywhere from a few tens of milleseconds to a few tenths of a second to get hot enough to set off the BP, so make sure your altimeter can supply the required current for 1 second. If you need more than 1 second to actuate the BP, you're using the wrong glow plug.

Finally, if you are going to fly HP after 10/16/06, at least for the short term, you are going to need a LEUP to buy the motors, and therefore you can buy e-matches without a problem. Don't make recovery any harder, or complicated than it needs to be, use one of the 4 established BP ignition methods discussed above with the currently available rocketry electronics and you'll be fine.

Bob

 

[rdm59]

I used xmas bulbs on my first dual-deploy. Works just fine.
I used shrink tubing and Hodgen triple7.

(Eat your heart out ATF, time to put xmas bulbs on the list!)

By the way, the Perfectflite HA45 altim. can provide up to 5 amps,
that should be enough to light higher amp draw solutions.


YMMV

 

[n3tjm]

I had 100% success with christmass bulbs till 2 flights had recovery failure. I determined that the bulbs were different in lots, even though all my bulbs were taken from the same brand of lights. Now I use e-matches. Now I am back to the drawing board....

 

[Rock_It]

.

 

[Rock_It]

.

 

[jderimig]

Originally posted by bobkrech


A high voltage capacitive discharge method, basically the same as above but with a spark plug instead of the resistor, will work if you want to custom design a multi-kilovolt electronics package, but why. It offers no advantage over proven existing methods so why do it.

I wouldn't say no advantages but maybe no practical advantages..

Some advantages:
1. No consumable bulbs or matches
2. More reliable. Bulbs are not 100% reliable (nothing is) and are one shot. With cd spark you can keep on sparking till boom.
3. Do not have to hook up anything, or less often.
4. Can double as a stun gun to keep pesky people away from your setup table.

Cons;
1. Weight
2. Safety

 

[shockwaveriderz]

rockit:

have you loked at skylighters ematch kits?

https://www.skylighter.com/mall/ignition.asp

scroll down and look at their ematch dip kit and their ematch chips

terry dean

 

[shockwaveriderz]

I wonder how good a CDI ignition or ejection charge system would be if you used some super caps?

terry dean

 

[jderimig]

Originally posted by shockwaveriderz
I wonder how good a CDI ignition or ejection charge system would be if you used some super caps?

terry dean

Super caps probably would not offer much advantage in a CDI system. CDI uses small capacitance (~1uf) but a high voltage (300-400v). Supercaps give mucho capacitance but at low voltage.

Basically you charge the cap to about 350v by switching the low voltage through a small transformer. Then discharge the cap through the primary of an ignition coil to generate the 10-25kv for the spark gap.

 

[bobkrech]

Originally posted by jderimig
I wouldn't say no advantages but maybe no practical advantages..

Some advantages:
1. No consumable bulbs or matches
2. More reliable. Bulbs are not 100% reliable (nothing is) and are one shot. With cd spark you can keep on sparking till boom.
3. Do not have to hook up anything, or less often.
4. Can double as a stun gun to keep pesky people away from your setup table.

Cons;
1. Weight
2. Safety

John

I disagree on the more reliable part.

E-matches, flash bulbs, christmas bulbs and glow plugs are very reliable provided you make sure the BP is in contact with the igniter, the BP compartment is hermatically sealed if the deployment is to be above 20 kft, and you have igniter continuity before you launch. Given these 3 conditions, I believe the probability of successful ignition of the BP charge is >99%.

The same contact and sealing requirements apply to a CD BP ignition system, and there is no continuity check possible. If the gap between the electrodes is not full of BP, you are not assured of ignition. If you were to put a thin bridgewire across the electrodes and make an exploding bridgewire ignitor (Bob Dahlquist's resistor system is a version of this), then you might have a theoretically more reliable system provided the CD portion of the system had redundancy as the high voltage components are more prone to failure than low voltage electronics.

NASA uses reduntant HV CD exploding bridgewire pyrotechnic systems for critical applications such as the pad holddown explosive bolts, SRB ignition, and other explosive bolt and staging applications where the all fire/no fire safety margins have to be high.

IMO if you want a system without consumables, a glow plug/barrel system like ATs is the way to go. It can be initiated by most conventional altimeter electronics and is without the hassle and weight of custom CD electronics.

Bob

 

[jderimig]

Fair enough Bob, makes sense to me.....

Originally posted by bobkrech
John

I disagree on the more reliable part.

E-matches, flash bulbs, christmas bulbs and glow plugs are very reliable provided you make sure the BP is in contact with the igniter, the BP compartment is hermatically sealed if the deployment is to be above 20 kft, and you have igniter continuity before you launch. Given these 3 conditions, I believe the probability of successful ignition of the BP charge is >99%.

The same contact and sealing requirements apply to a CD BP ignition system, and there is no continuity check possible. If the gap between the electrodes is not full of BP, you are not assured of ignition. If you were to put a thin bridgewire across the electrodes and make an exploding bridgewire ignitor (Bob Dahlquist's resistor system is a version of this), then you might have a theoretically more reliable system provided the CD portion of the system had redundancy as the high voltage components are more prone to failure than low voltage electronics.

NASA uses reduntant HV CD exploding bridgewire pyrotechnic systems for critical applications such as the pad holddown explosive bolts, SRB ignition, and other explosive bolt and staging applications where the all fire/no fire safety margins have to be high.

IMO if you want a system without consumables, a glow plug/barrel system like ATs is the way to go. It can be initiated by most conventional altimeter electronics and is without the hassle and weight of custom CD electronics.

Bob

 

[m85476585]

Originally posted by bobkrech
Recently AT has developed a clever reusable glow plug BP igniton system that is 100% effective when used as directed. A BP canister system employing a glow plug ignitor will work fine with any altimeter capable of delivering 2+ amps for 1 second. This is a bit different from altimeters that draw current from a capacitor to actuate an e-match. E-matches have low thermal mass and actuate in a few milleseconds so the capacitor does not have to be very large. A glow plug has a lot of mass and will take anywhere from a few tens of milleseconds to a few tenths of a second to get hot enough to set off the BP, so make sure your altimeter can supply the required current for 1 second. If you need more than 1 second to actuate the BP, you're using the wrong glow plug.

What voltage do they use? I made a circuit for my MAWD that lets it supply more current for a longer time.

 

[Rock_It]

.

 

[bobkrech]

The glowplugs used by AT require a current of 3 amps at 1.5 volts for 1 second. Most others will have similar requirements.

The ARTS supplies a maximum of 1.25 amps for 0.25 s. which is insufficient for glow plugs. Sorry.

Bob

 

[Rock_It]

.

 

[shockwaveriderz]

https://members.aol.com/nonillion/igniter.html

terry dean

 

[Rock_It]

.

 

[Art Upton]

Originally posted by Rock_It
.... I also plan to test some BP substitutes and will find equivelency for 2g charges...

Please note that BP substitutes are on the same list as BP, see smokeless powders are listed.

Just because you buy them at wally world does not mean you can treat them any different then BP you buy at the gun store or Pro Bass.

BP Substitutes only have a selling and storage exemption for "a component for use in small arms" or "a component in small arms ammunition".

Now, my Parachute Cannons are antique cannons anyway.

Smooth bore, muzzle loaded, nomex wadding with the parachute being the Ball.

 

[dwmzmm]

I used flashbulb ignition exclusively for launching my NAR competition & sport launch models back in the mid to late 1970's
and early 1980's, and had a 100% success rate. My confidence
in them were so high that I was more than happy to fly clusters
for the many demos I flew (mostly for my Estes Saturn - V and
Centuri Saturn 1-B), and the crowds just loved it!

When I returned to the hobby recently (after a 20+ year absence)
I used QuickBurst Hot Shot igniters, which are just as reliable and
dependable as flashbulb ignition, without all the prelaunch prep
hassles. I'm just hoping QuickBurst will get over with this mess by
the ATF so we can resume our enjoyment of flying clusters...

 

[Arnold Roquerre]

(edit) There are so many ways to come up with alternatives that will provide ematch type technology to everyone. One of the simplest is to use a miniature relay (e.g., https://www.radioshack.com/sm-5vdc-1...pi-2062480.html). The relay can be wired to stay closed once power is applied by any altimeter. The relay would then transfer power directly from a battery to the igniter which can be a wire with nichrome or a strand of wire from a steel wool pad soldered to a two lead wire wrapped in FFFF (note: there are other ways to make things go boom without using FFFF using sources far more ubiquitous and easily accessed, just in case the BATF takes FFFF away). The relay can be glued directly to the back of a 9 volt battery or attached to the altimeter board. It is light and cheap. Note: the relay has a 50/50% of being fried closed, so treat it as a throw away. The relay can be inserted up side down if high g forces are involved, or a two relays system could be used. One relay would be normally open and the other normally closed. If the Normally Open closed the Normally Closed will open. Now, we have a set up that can supply full battery output to any wire set used.

 

[jderimig]

Originally posted by Arnold Roquerre
(edit) There are so many ways to come up with alternatives that will provide ematch type technology to everyone. One of the simplist is to use a minature relay (e.g., https://www.radioshack.com/sm-5vdc-1a-spdt-micro-relay--pi-2062480.html). The relay can be wired to stay closed once power is applied by any altimeter. The relay would then transfer power directly from a battery to the ignitor which can be a wire with nichrome or a strand of wire from a steel wool pad soldeed to a two lead wire wrapped in FFFF (note: there are other ways to make things go boom without using FFFF using sources far more ubiquitous and easily accessed, just in case the BATF takes FFFF away). The relay can be glued directly to the back of a 9 volt battery or attached to the alimetery board. It is light and cheap. Note: the relay has a 50/50% of being fried closed, so treat it as a throw away. The relay can be inserted up side down if hight g forces are involved, or a two relays systme could be used. One relay would be normaly open and the other normaly closed. If the Normaly Open closed the Normaly Closed will open. Now, we have a set up that can supply full battery output to any wire set used.

Make sure you put a diode across the coil (against the energizing current flow). The back emf when the coil de-energizes can easily fry the altimeter output stages.....

 

[Arnold Roquerre]

If you are using a separate battery, would that be necessary?

----------------------------------------------------------------------------------

Make sure you put a diode across the coil (against the energizing current flow). The back emf when the coil de-energizes can easily fry the altimeter output stages.....

 

[UhClem]

Originally posted by Arnold Roquerre
If you are using a separate battery, would that be necessary?

----------------------------------------------------------------------------------

Make sure you put a diode across the coil (against the energizing current flow). The back emf when the coil de-energizes can easily fry the altimeter output stages.....

Absolutely.

The relationship between voltage and current in an inductor is:

V = L di/dt

Or, the voltage is proportional to the rate of change of the current. When you open up the switch/ transistor driving the coil, you are attempting to create an infinite di/dt. While real world things like coil resistance prevent an infinite voltage, it can still be very large. In fact, some DC/DC converters use this to generate very high voltages. (See recent article in Nuts & Volts where this phenomena is used to generate 200V from a 5V power supply.)

When you shut off the drive to the coil, the current still wants to flow. The voltage will tend to increase until it does. Thus the need for a diode to provide a safe path. Without it, the transistor/FET/swtich driving the coil is likely to have a very short life.