Simple timer system recommendation

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Rex Fynns
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Simple timer system recommendation

Postby Rex Fynns » Wed Sep 27, 2017 4:15 pm

G'day Folks,

I am in the market for a simple timer deployment system, I will likely only being using a single chute deployment initially but possibly progress to dual staged deployment.

I am a novice but recently built the Eggfinder system without any real difficulty, which works fine, I was also very impressed with the helpfulness and support from Cris, so more than happy to use his little Eggtimer.

However perhaps there is something that for around the $50 mark would be better.

Anyone have an opinion on timers?

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Re: Simple timer system recommendation

Postby OverTheTop » Wed Sep 27, 2017 5:41 pm

Timers are generally ok for staging, but for deployment altimeters are the norm.

I fly Featherweight Ravens and Altus Metrum Telemegas generally. Eggtimer also do an altimeter kit, they even have a WiFi enabled one I think. There are some cheapish altimeters to be found.

Give on a go and you won't go back to motor ejection (or timers :wink: ) again.
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Re: Simple timer system recommendation

Postby Rex Fynns » Wed Sep 27, 2017 10:26 pm

Thanks OTT,

Give on a go and you won't go back to motor ejection (or timers ) again.


I have no doubt about that.

I had a look at both the units you described, very impressed with their small size and capability, not cheap though and I am still in the losing and wrecking stages of the hobby.

The Eggtimer Quark is basic, the first baro detected signal for the drogue is at apogee or can be set up to 1 second after apogee, the second baro signal for the main can be set for various altitudes below 1000'.

At $20 USD it is pretty cheap and although you have to assemble them, I enjoy the challenge and skill process of doing so, I'm thinking I might grab a couple or 3 for that price.

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Re: Simple timer system recommendation

Postby OverTheTop » Thu Sep 28, 2017 7:29 am

The Quarks are great if you need low $ altimeters. Just follow the instructions carefully, and maybe ask some questions here, and you will end up with functioning altimeters.

The TeleMegas are particularly expensive to purchase. The design is open-source, so I could consider making my own to reduce the $400USD price tag. Time is my biggest problem though. Never enough for rockets :(
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Re: Simple timer system recommendation

Postby drew » Fri Sep 29, 2017 10:29 am

Hi Rex,

If you have a look a the tread below this one you'll notice a "magnetic apogee detector + timer" thread. In there's a link to a Magnetic apogee detector as well as timer that is $59usd. A little more pricey than what you might be after but it would be dead simple to use for apogee deployment.
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Re: Simple timer system recommendation

Postby Rex Fynns » Sat Sep 30, 2017 11:19 pm

G'day Drew,

That is a neat little device, I suspect a flux gate system for apogee detection is the way to go, odd they didn't seem to make it a dual deploy baro for a lower altitude main deployment, guess they will soon though, or I miss read the specs.

Not sure what the sport uses as a safety redundancy system for wayward rockets but with a flux gate style of system paired with a timer armed at takeoff the possibility exists to have a deployment in the event of a non vertical initial flight path. Not sure if that concept is desirable though??

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Re: Simple timer system recommendation

Postby Stewart » Sun Oct 01, 2017 1:54 am

Another ready built cheap alt is :- http://www.ebay.com.au/itm/Mini-AltiDuo ... 1438.l2649
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Re: Simple timer system recommendation

Postby Rex Fynns » Sun Oct 01, 2017 10:14 am

Hi Stewart,

That's what I was looking for, I didn't even consider searching ebay, the price is right too.

I had a look at the Bear Altimetry web site and have concluded that whilst the little Altiduo SMT is effectively the same as what Cris Erving is offering although you have to assemble Cris's product.

Cris's customer support is likely going to be better, his web site is very helpful and past experience dealing with him with the Eggfinder was second to none. I could not find info on whether or not the Altiduo is mach proof, the Eggtimer is.

So I'll place an order with Cris for a Quark.

If anyone wants an Eggtimer/finder etc. product from Cris and wants to save a $$ or two on shipping let me know (PM me if you wish) and I can include it with my purchase and send it on when it arrives, I'll place an order Tuesday.

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Re: Simple timer system recommendation

Postby kopius » Sun Oct 01, 2017 1:06 pm

We generally recommend avoiding timers for recovery as they are more of a 'hail Mary' type device and we have seen far too many issues with incorrect configurations or wayward rockets relying on an event that is either too early or late.

In saying that, if there is an automated process e.g. an altimeter with a trigger + timer, that is far better, but as OTT mentioned, often this is for staging etc. or known descents from a set altitude (again if there is baro or similar available).

Looks like you may have some cheap altimeter options from the other posts, but do your research to confirm their reliability.
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Re: Simple timer system recommendation

Postby OverTheTop » Sun Oct 01, 2017 6:15 pm

I suspect a flux gate system for apogee detection is the way to go


The current crop of magnetic sensors are much simpler than the fluxgate compasses. They basically have magnetically sensitive resistors (in a bridge configuration IIRC) and the support circuitry around that to provide degausing functions and usually a calibrated output.

Fluxgate was great in its time (1970's I think), but silicon technology has progressed, much to our advantage :)

I used to like the idea of a magnetic apogee detector, better than baro based altimeters. I have flown them quite a few times, in both simple and microcontroller monitored versions. Nowadays I just normally use Ravens and TeleMegas that deploy on baro.

Feel free to give the MAD (magnetic apogee detection) systems a go. They work. The single-axis analog sensors are getting harder to get (obsoleted by the manufacturer), and a lot of the magnetometer chips these days are I2C or SPI serial interface, therefore requiring a microcontroller life-support system. If you end up with a big horizontal component in your velocity at apogee the MAD system will probably make deployment a bit more severe on your rocket (likely deploys later, depending on how you have it set and which direction it is facing).
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Re: Simple timer system recommendation

Postby Rex Fynns » Sun Oct 01, 2017 9:04 pm

Kopius,

We generally recommend avoiding timers for recovery as they are more of a 'hail Mary' type device and we have seen far too many issues with incorrect configurations or wayward rockets relying on an event that is either too early or late.


Perhaps Eggtimer is a bit of a misnomer they are baro.

OTT,

Sorry my knowledge of flux systems and magnetometers is pretty basic in so far as I understand the basic principals, I am aware that the modern generation of sensors are as small as match head and can easily run to decimal points of a degree but beyond that I start to grey out a little.

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Re: Simple timer system recommendation

Postby kopius » Sun Oct 01, 2017 9:11 pm

Rex Fynns wrote:Perhaps Eggtimer is a bit of a misnomer they are baro.

Then they aren’t just a timer and should be more reliable.


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Re: Simple timer system recommendation

Postby OverTheTop » Mon Oct 02, 2017 6:37 am

Sorry my knowledge of flux systems and magnetometers is pretty basic in so far as I understand the basic principals, I am aware that the modern generation of sensors are as small as match head and can easily run to decimal points of a degree but beyond that I start to grey out a little.


No sweat. Just informational! I remember buying the magazine that brought the fluxgate magnetometer to the public attention. Wireless World, 1982. I think I still have it. One of the few I deemed worthy to keep.
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