Pyro Firing Times - How long to fire e-matches?

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I'm using a Altus Telemega and saw you can set the Pyro Firing Times. Is there a recommended duration when firing e-matches with a 1S LiPo (800Mah), does the recommendation change if I add a 2S as a separate Pyro battery?
 
I'm not sure what you are asking. Is Pyro Firing Times the duration of the firing pulse, or the amount of time between some event and the start of the pyro firing?

I've don't have the telemega, but none of the altimeters I've had allow setting the width of the firing pulse. Most are fixed at 1 second. What they do allow is adjusting how long after a trigger event the firing pulse occurs. The most common is the delay after apogee event. If your altimeter is the back-up in a two altimeter system, you might want the firing delayed a second or two after apogee.
 
Yes, with TeleMegas you can set the duration of the firing pulse on the Pyro channels. You can't set them on the Main and Apogee channels as you noted.

I'm using the Pyro channels for staging, first for separation, then ignition. Upper stage is Cesaroni Red Lightning 38mm which uses a e-match type igniter.

1 seconds seems too long for an e-match. I'm thinking between .1 and .5 seconds, probably going to use .25.
 
Yes, with TeleMegas you can set the duration of the firing pulse on the Pyro channels. You can't set them on the Main and Apogee channels as you noted.

I'm using the Pyro channels for staging, first for separation, then ignition. Upper stage is Cesaroni Red Lightning 38mm which uses a e-match type igniter.

1 seconds seems too long for an e-match. I'm thinking between .1 and .5 seconds, probably going to use .25.

Would a 1 second pulse hurt you? Most e matches fire pretty fast. That said, I cannot see how a 1 second pulse will hurt you.

The above said, I do not have much knowledge of the Telemega. What are the outputs rated at and what is the resistance of the e match?
 
The ematches tend to open when fired and current flow will stop even if the pyro channel stays on a bit longer. I can understand why there would be no adjustment for the main and apogee channels since they would always be used with matches. With that said, maybe the adjustment of the pyro channels is so they can be used with other things beside matches. I think I would leave the channel at 1 second like the main and apogee if I was using it for matches since I can't see an advantage in shortening it.
Just MHO
 
The ematches tend to open when fired and current flow will stop even if the pyro channel stays on a bit longer.

If I understand correctly this is one of the reasons I can't figure the "series" wiring thing vs. "parallel" when trying for redundancy....or cluster airstarts -

If an ematch fires but fails to completely ignite, - ie. pops the pyrogen off, doesn't that break the chain?
 
If I understand correctly this is one of the reasons I can't figure the "series" wiring thing vs. "parallel" when trying for redundancy....or cluster airstarts -

If an ematch fires but fails to completely ignite, - ie. pops the pyrogen off, doesn't that break the chain?

The firing time is so fast that it does not matter. If you are using Lipo’s, which can source a lot of current, and you do not want to the have your resistance too low- you could over current the output transistors and fry them. The devil is in the details- ohms law is a useful tool. You need to look at this from source to match. What can the battery source? What can the output circuits take, and are they current limited? What is the resistance of the load/ematch?
 
The firing time is so fast that it does not matter. If you are using Lipo’s, which can source a lot of current, and you do not want to the have your resistance too low- you could over current the output transistors and fry them. The devil is in the details- ohms law is a useful tool. You need to look at this from source to match. What can the battery source? What can the output circuits take, and are they current limited? What is the resistance of the load/ematch?

Thanks, - I read the big redundancy thread awhile back (IIRC discussion may have mentioned that) and I still wasn't getting it.
Makes sense, I guess.
 
Last edited:
Thanks, - I read the big redundancy thread awhile back (IIRC discussion may have mentioned that) and I still wasn't getting it.
Makes sense, I guess.

What part are you not sure of?
 
If I understand correctly this is one of the reasons I can't figure the "series" wiring thing vs. "parallel" when trying for redundancy....or cluster airstarts -

If an ematch fires but fails to completely ignite, - ie. pops the pyrogen off, doesn't that break the chain?

Only if the bridge wire burns through causing an open circuit. The only times I’ve seen (or had) ematches fail without lighting they still had continuity.
 
If I understand correctly this is one of the reasons I can't figure the "series" wiring thing vs. "parallel" when trying for redundancy....or cluster airstarts -

If an ematch fires but fails to completely ignite, - ie. pops the pyrogen off, doesn't that break the chain?

When the current flows the bridgewire temperature starts to rise, quickly. If the ematches are in series the wire in each match heats at the same rate (nominally). The temperature that the pyrogen ignites is well below the temperature that the wire melts. So both wires will be well above the pyrogen ignition temperature before one of them melts and opens.
 
Only if the bridge wire burns through causing an open circuit. The only times I’ve seen (or had) ematches fail without lighting they still had continuity.

Also, ignitors used for airstarts can have a long time at high current because the gas inside the motor is highly conductive. If you use head-end ignition you can count on having a hard short for as long as the output is active.
 
Only if the bridge wire burns through causing an open circuit. The only times I’ve seen (or had) ematches fail without lighting they still had continuity.

I had several ematches that tested about 0.7 ohm and failed to fire and where open afterwards. I fact, I had two on the same flight, both different brand commercial ematches. Fortunately the rocket fell flat from 4400 ft and was recovered without damage. Should have bought a lottery ticket that day!
 
I had several ematches that tested about 0.7 ohm and failed to fire and where open afterwards. I fact, I had two on the same flight, both different brand commercial ematches. Fortunately the rocket fell flat from 4400 ft and was recovered without damage. Should have bought a lottery ticket that day!

Wow!
 
I had a successful flight last weekend using .25 sec for the pyro times for the separation charge and sustainer igniter (e-match). The battery was a 1S 800 mah. I also learned that it took 1.2seconds to achieve pressure after the igniter fired for the CTI H120-RL in the sustainer.
 
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