I put this up on Facebook and then realized this is the better place to discuss this. And this may have been beaten down in the past, but I'm new to the group, so my apology.
First - On Facebook I asked this: I was putting together my list of electronics and accessories to buy for my current project and foreseeable future projects. I had planned on using the Easymini as my redundant computer (with a Telemetrum as the main) when I noted its bottom of voltage operation range is 3.7 volts, which is right at the fully charge single cell lipo rating. (It would seem it was designed for a 9V, which I'd rather avoid using if possible.) It's got a voltage range of 3.7V-12V per the website, but it would seem that it would require a 2 cell lipo to get above that minimum voltage. That would mean a different charger and other complications. And then I'd have to find a 2-cell lipo without the current limiting built in. I also noted the manual makes this statement- "EasyMini and TeleMini v2 are designed to use either a lithium polymer battery or any other battery producing between 4 and 12 volts, such as a rectangular 9V battery." So while its says it will operate at 3.7 on the website, the manual seems to point you back to above 4 volts supply for the Easymini. And if it does run on 3.7V, (which appears to be the ragged edge) it would seem that using a separate pyro battery would be a must to keep the processor's voltage from sagging during a pyro event. (It's not a big deal to run a separate pyro battery.) I was told on Facebook that a single cell lipo reads 4.2 volts when fully charged. After a bit more looking, I found this study on Lipos from USC which includes discharge rates VS voltage on page 18. http://www-scf.usc.edu/~rzhao/LFP_study.pdf So it would seem that I may have had my questions answered, but thought I'd still post here. It seems I can indeed run the Easymini on a single cell lipo, use a separate pyro battery to keep the processor's supply rail on the Easymini from dropping below 3.7V and everything will function properly. If I'm missing something or have misinterpreted something, please let me know. Thanks, Scott Myers From: altusmetrum [mailto:[email protected]] On Behalf Of Reinhard Rath Sent: Monday, May 15, 2017 5:59 AM To: Keith Packard; [email protected] Subject: Re: [altusmetrum] Behaviour of EasyMini on high altitude flights exceeding sensor range On 09.05.2017 at 19:20 Keith Packard wrote: I really haven't thought much about flying EasyMini above 100k' -- lacking any additional sensors, you're essentially flying a timer. As you say, you might be able to get it to also perform recovery if the flight didn't go as expected. Thanks. I think we will try this route. EasyMega, with its ability to detect rotation, would be a far better choice as you could program it to fire the apogee event when the airframe tilted over by more than 90 degrees. This is a very reliable indication of apogee, and fails only when the rocket back-slides. EasyMega won't easily fit in our ebay. That being said, I'm kinda concerned when and how the rocket finally tilts over (probably a good bit after apogee, given the low density atmosphere and maybe some spin) and for how long the tilt detection stays accurate (gyro drift on extended flights). Reinhard
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