Thanks Steve,
Got it. Yes, that would be a great experiment - maybe if you have some
ventilation you
won't have the problem taking some of this equipment outside to pop
ematches ... let
me know if you'd like to meet up and do some experiments like that sometime
... I use
a cart and UPS to do all my RvR testing in the garage... would be perfect
for ematches.
-James
On Tue, Jul 14, 2015 at 8:17 AM, Steve Sawyer <steve@xxxxxxxxxxxxxxxx>
wrote:
Yes, it's mostly short protection. I would like to run an e-match
time-current curve (I have a curve tracer in the lab).
Steve
*From:* tccrockets-bounce@xxxxxxxxxxxxx [mailto:
tccrockets-bounce@xxxxxxxxxxxxx] *On Behalf Of *James Dougherty
*Sent:* Tuesday, July 14, 2015 7:45 AM
*To:* tccrockets@xxxxxxxxxxxxx
*Subject:* [tccrockets] Re: battery for stratologger CF
Hi Steve
Yes, but the e-match fires with much less current before the FET fails...
And those FETS ... They can take short pulses of current far beyond
What they are rated for ...
Anyhow, I thought that may be an issue but I haven't had a problem with
the setup using ematches.
I think the concern is if the ematch fires but somehow the leads get
shorted - I can see that messing things up and maybe even
actually starting a fire!
Thank you
-James
Sent from my iPhone
On Jul 14, 2015, at 7:06 AM, Steve Sawyer <steve@xxxxxxxxxxxxxxxx> wrote:
I agree with Bob, if you want to turn to later technologies, the 2S LiPo
is a very nice small package - just watch out for the FET rating for firing
the pyros. A 180mA LiPo with a 40C rating means that it can deliver 7.2A
into a 1 Ohm pyro load (this exceeds the PerfectFlite 5A FET rating).
I've also had discussions with PerfectFlite - they are fairly clear about
recommending the 9V Alkaline batteries (9V NiMH can also be used from
Harbor Freight).
However, I'm using a 3S LiPo (Turnigy nano-tech 180mah 3S ~40C from
HobbyKing or Amazon). This is very small but as I mentioned, requires the
added series resistors on the outputs. The voltage regulator on the
PerfectFlite will allow operation from either a 3S or 2S LiPo.
Steve
*From:* tccrockets-bounce@xxxxxxxxxxxxx [
mailto:tccrockets-bounce@xxxxxxxxxxxxx <tccrockets-bounce@xxxxxxxxxxxxx>] *On
Behalf Of *Bob Feretich
*Sent:* Monday, July 13, 2015 6:43 PM
*To:* tccrockets@xxxxxxxxxxxxx
*Subject:* [tccrockets] Re: battery for stratologger CF
7.4V LiPo (Li-Ion) will work in 95% of all 9V alkaline battery electronics.
The rated voltages are confusing because that 9V alkaline battery
advertises its starting voltage and the 7.4V LiPo battery advertises its
discharged voltage.
Compare the discharge curves...
http://www.feretich.com/Rocketry/Resources/lipotests.html
http://www.feretich.com/Rocketry/Resources/Pdfs/7v%20Li-Po%20vs%209v%20Alkaline.pdf
Assuming your electronics draw 100 mA of current, the cross-over point is
at 30 minutes of use. After 30-minutes, the voltage of a 7.4 V LiPo is
greater than a fresh 9V Alkaline.
A fresh (newly manufactured) 9V alkaline battery starts at 9.25V, drops to
9V after about 7 minutes of use (at 100 mA), and to 7.4V after about 2
hours. (If the battery has sat on the shelf for a while, it may start at
8.4V.) See the discharge curve at the provided link. One alkaline battery
was freshly manufactured the other had one month still remaining before its
expiration date.
A fully charged 7.4V LiPo starts at 8.4V and declines slowly to 7.4V.
Below 7.4V, the voltage on LiPo (and Li-Ion) batteries drops quickly.
Given that at the end of its rated life, a 9V alkaline battery is only
sourcing 7V, electronics designed correctly to use 9V alkaline batteries
will work fine with 7.4V LiPo batteries.
Regards,
Bob
On 7/13/2015 3:02 PM, Mike Hubble wrote:
Manual says standard 9v is all you need.
On Mon, Jul 13, 2015 at 2:39 PM, Peter Hackett <
peter.hackett@xxxxxxxxxxxxxxxx> wrote:
I've always used a standard 9V alkali battery. Never had any battery
problems with it.
On Mon, Jul 13, 2015 at 2:07 PM, Steve Sawyer <steve@xxxxxxxxxxxxxxxx>
wrote:
I've been using 180mah 3S 25~40C Lipos.
For the stratologger CF required protection of the FETs (i.e.,
short-circuit or 1 Ohm pyros), I use series 3 Ohm resistors on each output.
Lots of flights are possible.
Steve
*From:* tccrockets-bounce@xxxxxxxxxxxxx [mailto:
tccrockets-bounce@xxxxxxxxxxxxx] *On Behalf Of *Ben Sandoval
*Sent:* Saturday, July 11, 2015 11:01 AM
*To:* TCC Chat
*Subject:* [tccrockets] battery for stratologger CF
Which battery are you using for your stratologger cf. I'm getting ready to
order a few batteries and I'm still on the fence. Appreciate your input.
