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AlexM

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Here is my dillema. I have a Perfectflite timer with a built in G switch. I have been using a simulated breakwire to test it. I have it hooked up to one 9 volt battery, and tested it on an estes ematch first. It worked, so I moved on to the copperhead. I could not get it to fire. Figureing that the copperhead was just living up to its reputation, I got a brand new one out of the package and it still would not light. I am lighting two F's on the pad with an airstart on a G., and instead of copperheads, I am using the more reliable and conventional Firstfire Jr. ignitors. I only have three, and not enough time to get more before the launch.:kill: I was wondering, is it the ignitor or the battery?
 

Omega_D

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Most definitely the copperhead. These igniters take a ton of current, and they are notorious for being shorted right out of the package. I'm not familiar with the igniters you're going to use but I'm guessing that if you can light an Estes igniter, you shouldn't have any problems.

My $0.02
 

Stymye

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sometimes the edges of the copperhead are rounded over (from the cutter/shear mabey?)..I have read that scraping the edge helps..haven't tried it myself
 

Justin Horne

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That's true, but most copperheads won't light without a 12 volt system, drawing quite a few amps, that I'm almost certain the timer couldn't give. And if you are going to be clustering, you might get into dipping your own...
 

AlexM

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Can the timer light a firstfire?
 

Zippy

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First Fire's are also meant for 12 volt systems. You really need a low current dipped ematch. Something like a Daveyfire N28-B dipped in Magnelite. They could be hard to get into the nozzle of SU motors but with reloadables you can assemble them with the ignitors inside.
 

bobkrech

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Tarc3

There's a lot of really useful and practical information in the manual for the timer where they discuss these issues.

http://www.perfectflite.com/Downloads/UT2MT3manual.pdf

Are you using their recommended 9 volt battery? Most 9 volt batteries will not supply enough current because their internal resistance is too high. Check out page 10 for the info on the batteries and on which ignitors have been shown to work with the timers.

The current capacity of the timer is not the issue. The energy is stored in a capacitor and it will deliver 40 amps into a short which is plenty of current for any ignitor, provided you use heavy gauge wire (at least 18 or better 16 gauge wire.)

The biggest problem for firing a copper head may be the voltage limitation with the Perfectflite timer. It is designed to operate on a 9 volt battery (max voltage 10.5 volts). A 12 volt direct ignition system delivers at least (12/9)^2= 1.77x (and in practice probably >3x) the power to the ignitor so it is possible that you can't deliver the required power to light a copperhead.

Bob Krech
 

AlexM

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Thanks, I justg bought a box of 30 Daveyfire 23F igniters and some firestar pyrogen, so i feel confident that it will work now...:rolleyes:
 

UhClem

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Bob,
Judging from the manual, that big capacitor on the Perfectflight timer is there to provide power to the electronics in the event that the battery voltage drops too low when firing the igniter. The manual says that the timer has "brownout protection" and this would be it.

If it were there to fire the igniter, it couldn't possibly store enough energy to light a Copperhead. It would only work with low energy igniters like the Daveyfire and Oxral.
 

bobkrech

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David

Good point. You're absolutely right about the cap. I missed that the cap is for brownout protection only and not for the pyro.

Perfectflite uses a honkin FET transistor that can pass 40 amps in the timer pyro circuit, but they specify that the maximum input voltage is only 10.5 V. That's only an 8 NiCad or NiH cell pack at the most, but I think that the timer will reliably fire a copperhead if you use a low impedence battery. (Not that you have to or should since there are better ignitors for airstarts.)

While there is little question that the timer can deliver sufficient current to fire a copperhead, and as most Copperheads are fired with a 12 volt system (drawing up to 20 amps peak), there may not be enough voltage behind it to develop the power required to reliably fire the copperhead.

I could not find a definative statement on the electrical resistance properties of a copperhead, but I was able to find the patent and the instructions for copperheads on the Aerotech website. The operationing instructions states that a 12 volt ignition system capable of delivering a minimum of 3 amps or more to the ignitor is sufficient to fire the ignitor.

http://www.aerotech-rocketry.com/cu...oryDocuments/Patents/copperhead_5123355#1.pdf

http://www.aerotech-rocketry.com/cu.../Misc_Instructions/how_to_use_copperheads.pdf

Using the experimental data on Copperhead igniton at the reference below, I have analyzed the ignition data from Figure 3 which shows that it takes about 10 amps from 12 volt launcher to promptly fire the copperhead. (That's determined by the initial current surge, and my interpretation that the later time current rise is due to a conductivity increase in the hot propellant gases.) After doing the math, that would make the resistance of the copperhead approximately 1 ohm, and using Aerotech's 3 amp all-fire rating, if you can deliver at least 3 amps into a 1 ohm load, you can fire a copperhead. (That's a voltage of 3 volts developed across the copperhead.

http://www.gwiz-partners.com/igniters.pdf

If my interpretation and assumptions are correct, using the data from page 11 of the Perfectflite manual, I predict that Sanyo 7.2 NiCad battery and last 3 rechargable battery packs will fire a copperhead if that's what you want to do.

http://sanyo.wslogic.com/pdf/pdfs/N-6PT.pdf

I don't have a PerfectFlite timer, but it would be a fun one to try.

Bob Krech
 

XAVIEN

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It sounds like your battery can't support the requirements of the E-match, as many people have stated already. This is more of an FYI then anything, when designing my timers I tested various e-matches for the outputs. I found that the QUICKBURST "HOTSHOT" e-matches work like a champ. I have used one of my "XCIC-1" to start 5 motors using these bad boys. If you are airstarting something I would really recommend using another product, the Copperhead is notorious for its current / voltage requirements.

Good luck,
Steve
 

jwagner61

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Hi all,

Being somewhat new to the hobby and just starting to use electronic deployment, the topic of this thread is of great interest.

Bob Krech's information is particularly useful, especially the link on the 7.2V Sanyo NiCd cell specification. However, the current for the high rate discharge curves appears to be confusing. The curves are labeled 4 lt, 2lt and 1 lt. It seems clear that these are related to test current loads, but the units are not amps.

Using a capacity of 110 mAh and an approximate discharge time of 10 min for the 4 lt load gives an average current of 0.660 mA (0.66 A ) for the actual current.

The discussion seems based on a 3 A load, 5 times that for the 4 lt data. It's not clear to me that any NiCd "9 V" battery can actually deliver this type of current, even if its just for 5 seconds.

I've done tests on 7-cell, 8.4V NiCd batteries and have found these don't even come close to sourcing 1 amp even at a few volts.

The 6cell, 7.2V NiCd batteries may be better, but I'm not sure they can reliablely light anything that requires a 3 A load. Just what I've observed in my own tinkering. I would appreciate comments from those with more experience.

Thanks,
John Wagner
 

bobkrech

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John

From what I gather, Perfectflite did current measurements for the Sanyo battery and present the test results on page 11 of the timer manual. I performed a sanity check to his numbers by simply using the internal resistance of the battery as measured at 1000 Hz in the Sanyo data sheet to determine the short circuit current delivered for a millesecond.

R = .210 ohms, V ~ 8 volts, I = V/R = 8/.21=38 amps for 1 msec.

You can't pull that much current for a second due to diffusion limitations and other physical chemical phenomenon within the battery. (I won't go into details here, because it 's pretty high level chemistry.) (To add to the confusion, the Sayno data sheet use "lt" as the 1 hour rate current instead of the "C" (Capacity in AH) that is found in the American data sheets.)

The point I was trying to make (which was also pointed out by Steve) was that you have to pick out the right battery to fire high current ignitors. It's the current, not the voltage that fires an ignitor, and the internal resistance (impedence) of the battery is the determining factor. (The voltage is simply the force required to push the current through the circuit.)

For a given A-H capacity, a battery with a low internal resistance can deliver higher currents for shorter periods of time than a same capacity battery with a higher internal resistance.

Modern NiCad and NiMH batteries in a "9 volt transistor battery case" are made from either 6, 7 or 8 individual batteries connected in series rated at 7.2, 8.4 and 9.6 volts respectively.

Most 7.2 volt versions are made by packaging 6 1.2 volt cylinderical "AAAA" cells in the case. The cells have a large electrode area and therefore have a low internal resistance and are designed to deliver a lot of current in a short period of time. The 8.4 volt versions are typically 7 "pancake" cells with a relatively small electrode area (higher resistance) which is good for supplying lesser currents for longer periods of time. (The 9.6 volt versions are relatively new and I don't know much about them but are most likely "pancake" construction.)

Only the 7.2 volt versions can deliver the currents required to fire ignitors promptly.

What most folks don't know is that the most rapid ignition of an ignitor occurs when the resistance of the timer circuit is equal to that of the ignitor. That because the maximum possible power is being delivered to the ignitor so it heats up in the shortest possible time. I have attached a graph of the power delivered to an ignitor as a percentage of it's resistance in the firing circuit. For example if the ignitor has a resistance of 1 ohm, optimum igintion speed occurs when the resistance of the battery, firing circuit, and wires equals 1 ohm, but anything less is ok because that means you get higher current than required but it is way about the minimum all-fire current. If the circuit resistance is greater than that of the ignitor, you might not be able to deliver the minimum all fire current if the battery is not fresh.

Most ignitors are not well characterized, but DaveyFire had some great info that is no longer posed. For their e-matches, a current 3x larger than their all-fire rating usually resulted in a sub-millesecond ignition delay.

Hope this is not too confusing.

Bob Krech
 

shockwaveriderz

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you might want to consider using some super capacitors in place of batteries:

http://www.cooperet.com/products_supercapacitors.asp

I know of at least one instance where a modeler replaced batteries with these super caps and his perfectflite micro timer can now fire estes igniters all day long......

They also have a handy excel spreadsheet there to determine the optimal super cap to use.....

check out the series B 1-50 FARADS!!!!
 

Rockaholic

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Originally posted by XAVIEN
It sounds like your battery can't support the requirements of the E-match, as many people have stated already. This is more of an FYI then anything, when designing my timers I tested various e-matches for the outputs. I found that the QUICKBURST "HOTSHOT" e-matches work like a champ. I have used one of my "XCIC-1" to start 5 motors using these bad boys. If you are airstarting something I would really recommend using another product, the Copperhead is notorious for its current / voltage requirements.

Good luck,
Steve
Hey Steve,
What battery did you use to start 5 motors?

I just started a thread on airstarting E9's....
I'm looking to start four with your XCIC (my first electronics project).
Anyway, is this possible with one 9volt battery? , if not could two 9volts be wired in parallel. Or, is there an alternate battery choice?
Looking forward to your reply. Thanks to you and the others here for all of the good info.
Dave
 

XAVIEN

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Dave,

I airstarted 5 Estes D motors using the XCIC-1 and HOTSHOTS. I wired the batteries in parallel and I used 2 of the SANYO "N-6PT" Nickel cadmium batteries. These batteries can momentarily source up to 20A fully charged, not bad for a 9V battery "size". You can get the batteries as well as the charger from PerfectFlite ( www.perfectflite.com ). Their part numbers are "NC9V" (battery) and "BC9V" (charger).

Best of luck!

Steve
 

stevem

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I too am waist deep in my first air-start project -

where does one buy Daveyfire ignitors?
 

Rockaholic

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Originally posted by XAVIEN
Dave,

I airstarted 5 Estes D motors using the XCIC-1 and HOTSHOTS. I wired the batteries in parallel and I used 2 of the SANYO "N-6PT" Nickel cadmium batteries. These batteries can momentarily source up to 20A fully charged, not bad for a 9V battery "size". You can get the batteries as well as the charger from PerfectFlite ( www.perfectflite.com ). Their part numbers are "NC9V" (battery) and "BC9V" (charger).

Best of luck!

Steve
Thanks Steve. I started the air start project as a "gentle" introduction to electronics....based on how economical your air start boards are.

I now see, like everything in this hobby, that it can add up fast (the batteries will cost more than the electronics).

Quick quesition, do you think one N-6PT battery could light 4 E9s (using hotshot ignitors)?

Is there a reason you used 2 batteries? (was this overkill or necessary).

I half way would like to keep weight down (too late for that) and cost down too (too late for that too!).
Dave
 

quickburst

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Originally posted by Rockaholic
Thanks Steve. I started the air start project as a "gentle" introduction to electronics....based on how economical your air start boards are.

I now see, like everything in this hobby, that it can add up fast (the batteries will cost more than the electronics).

Quick quesition, do you think one N-6PT battery could light 4 E9s (using hotshot ignitors)?

Is there a reason you used 2 batteries? (was this overkill or necessary).

I half way would like to keep weight down (too late for that) and cost down too (too late for that too!).
Dave
Buy the batteries at:
http://www.nicdlady.com/

You can get them for half the price, you have been quoted.
 

BobCox

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Originally posted by bobkrech
What most folks don't know is that the most rapid ignition of an ignitor occurs when the resistance of the timer circuit is equal to that of the ignitor. That because the maximum possible power is being delivered to the ignitor so it heats up in the shortest possible time. I have attached a graph of the power delivered to an ignitor as a percentage of it's resistance in the firing circuit. For example if the ignitor has a resistance of 1 ohm, optimum igintion speed occurs when the resistance of the battery, firing circuit, and wires equals 1 ohm, but anything less is ok because that means you get higher current than required but it is way about the minimum all-fire current. If the circuit resistance is greater than that of the ignitor, you might not be able to deliver the minimum all fire current if the battery is not fresh.
Um, not quite right.


{Equation 1} IgniterPower = IgniterResistance * IgniterCurrent^2,
{Equation 2} IgniterCurrent= BatteryVoltage / (IgniterResistance + ParasiticResistance),
where ParasticResitance is the internal resistance of the battery, plus the resistance of leads, connectors, switches, relays, etc.

Combining equations {1} and {2}, we get
{Equation 3} IgniterPower = BatteryVoltage^2 * IgniterResistance /(IgniterResistance+ParasiticResistance)^2

Bob K's graph is correct if you are working with a fixed parastic resistance and can vary the igniter resistance. Note that for very small igniter resistance, the numerator is small and the igniter power is also small. For very large values of igniter resistance, the denominator get huge and again the igniter power is small. The maximum igniter power will occur when the the igniter resistance matches the parasitic resistance.

However, the reverse is not true. If you are using a fixed igniter resistance, then maximum igniter power happens when the parastic resistance is zero. If parasitic resistance is increased until it matches the igniter resistance, the total current will be cut in half and the igniter power will be one-fourth.

Parasitic resistance is all bad, and should be minimized wherever possible.
 

gregzo

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Hopefully this is not considered hi-jacking the thread - but I have some other questions on airstarts.
Dave B - love your products. I love your Twiggy's for 24/40 and 29/40-120 motors. I also used your FatBoys for the first time on an AMW K560RR and an AMW L1100RR in June - both lit with no problems!!
Anyway - Sounds like the HotShot is just the ticket for airstarting BP motors. What about AP? I am just starting a project with a central 54mm and two outboard 38mm mounts. What do you recommend for the 38mm's (or 29mm w/ adapters) outboards for airstarting? Most likely a pair of H128W. I have your M-Tec e-matches and have been using those for deployment. Is an M-Tec dipped in Magnalite a good combo for airstarts?
Steve (Xavien) - I plan on using your XDSRT-1 in this project. Is one battery sufficient for dual airstarts - or do you recommend a parallel double battery configuration (or maybe part of that answer is from Dave). Also - Did you get my e-mail about a custom timer with off board LEDs??
Thanks guys
 

XAVIEN

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Dave (Rockaholic) -

The HotShots work great, as do the Poppers. With a N-6PT battery you should have no problem lighting 4 of them. I have used HOTSHOTs for BP motors, no problems. I have tried using them standard to lite BP motors as an experiment, never worked (tried on an Ellis and Aerotech). I have never tried them "dipped", so I couldn't give you any info there. I used two batteries so I would have the old "warm fuzzy", I tend to over build sometimes.



Greg (Gregzo) -

I replied to your email a few days ago, perhaps it was "lost in the shuffle", I'll give it another go and forward you what I sent.


Dave (Quickburst) -

Thanks for the link, as always I learn something new everyday....


Best regards,
Steve
 

Rockaholic

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Awesome David!
You and Steve have been so helpful.
I'm getting my ignitor and electronics orders ready.
Thanks SO much!
Dave
 

jraice

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Would the micro timer light two CTI ignitor's?
 
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