The Eggtimer - A full-function multiple-deployment flight computer for only $40

[cerving]

The Eggtimer is a full-function barometric flight computer kit, featuring:

o Two high-current deployment channels (Main and drogue/airstart)
o Three logic-level channels (drogue, main, landing detect), easily interfaced to high-current drivers
o Outputs are opto-isolated from the low-voltage logic, completely brownout-proof
o Native support for standard R/C servos as well as igniters
o Connectors for external deployment continuity LEDs, buzzer, and Ready status LED
o 32-flight memory, sampling selectable from 4-33 samples/sec
o Kalman filtered altitude/velocity, "mach immune" so deployments can't happen until you're past apogee
o Airstart support, requires three events for ignition (breakwire, minimum altitude, burn/delay timer expiration)
o Flight summary downloadable as a standard text file
o Flight details downloadable as a standard .CSV file, can be imported into Excel or virtually any stat program
o Uses standard VT100/ANSI text terminal programs for programming, programmable with virtually any type if computer
o Eight pre-programmed flight profiles, so you can program it out in the field without a computer
o Easy to build, SMT parts are pre-mounted; you only have to solder the through-hole parts
o Operates from 3-4v, works great with a single 3.7V LiPo cell or a 3V lithium battery (like a CR123)
o $40 INCLUDING the USB-Serial data transfer cable

For more details, see www.eggtimerrocketry.com
Cris Erving
Eggtimer Rocketry
Questions? Drop us a line at [email protected]

 

[DAllen]

The Eggtimer is a full-function barometric flight computer kit, featuring:

o Two high-current deployment channels (Main and drogue/airstart)
o Three logic-level channels (drogue, main, landing detect), easily interfaced to high-current drivers
o Outputs are opto-isolated from the low-voltage logic, completely brownout-proof
o Native support for standard R/C servos as well as igniters
o Connectors for external deployment continuity LEDs, buzzer, and Ready status LED
o 32-flight memory, sampling selectable from 4-33 samples/sec
o Kalman filtered altitude/velocity, "mach immune" so deployments can't happen until you're past apogee
o Airstart support, requires three events for ignition (breakwire, minimum altitude, burn/delay timer expiration)
o Flight summary downloadable as a standard text file
o Flight details downloadable as a standard .CSV file, can be imported into Excel or virtually any stat program
o Uses standard VT100/ANSI text terminal programs for programming, programmable with virtually any type if computer
o Eight pre-programmed flight profiles, so you can program it out in the field without a computer
o Easy to build, SMT parts are pre-mounted; you only have to solder the through-hole parts
o Operates from 3-4v, works great with a single 3.7V LiPo cell or a 3V lithium battery (like a CR123)
o $40 INCLUDING the USB-Serial data transfer cable

For more details, see www.eggtimerrocketry.com
Cris Erving
Eggtimer Rocketry
Questions? Drop us a line at [email protected]

Just a suggestion, I would put some photos on your web site of the products and maybe even a video of the assembly process. Sounds like an interesting product.

 

[cerving]

Thanks, feedback is a good thing! At some point I'll probably put a picture of the Eggtimer on the top of the web pages, I've been too busy with development and now production to try to get too pretty with the web site.

There is a Photos section on the web site with step-by-step assembly pictures that go along with the assembly manual, so if you're not familiar with the various components you can get it sorted out. I'm not sure anybody would want to see a video though... watching me solder is like watching grass grow!

Just a suggestion, I would put some photos on your web site of the products and maybe even a video of the assembly process. Sounds like an interesting product.

 

[powderskierman]

Mine arrived today, thanks for getting it to me so quickly. The quality looks good. Time to practice some soldering before I dive in.

 

[cerving]

Any and all feedback is greatly appreciated! Thanks!

Cris Erving
Eggtimer Rocketry

 

[DAllen]

Thanks, feedback is a good thing! At some point I'll probably put a picture of the Eggtimer on the top of the web pages, I've been too busy with development and now production to try to get too pretty with the web site.

There is a Photos section on the web site with step-by-step assembly pictures that go along with the assembly manual, so if you're not familiar with the various components you can get it sorted out. I'm not sure anybody would want to see a video though... watching me solder is like watching grass grow!

Ahhh I see the photos section now. BUT I think photos of the final product ought to be on your products page. Sounds like you are on your way to making that happen though.

What I meant by the video would be maybe some examples of the soldering and/or installation of one of the parts. Something like a summary. Certainly not an entire assembly of course.

Gotta say, I am really liking the functionality to dollar ratio here even if there is a little assembly required. Nice!

-Dave

 

[Pantherjon]

I am really intrigued! Especially with the two-fer deal!

Quick question: If I order, what revision board would I get, A,B, or C? I presume C, but have to ask...

 

[cerving]

I can do that... I think. I'll have to admit that the web tool that I'm using is a little sketchy... I have lots of trouble getting the fonts right (I like Comic Sans Serif). I'll take a look at it, of course I need to make a soldering video first.

Ahhh I see the photos section now. BUT I think photos of the final product ought to be on your products page. Sounds like you are on your way to making that happen though.

What I meant by the video would be maybe some examples of the soldering and/or installation of one of the parts. Something like a summary. Certainly not an entire assembly of course.

Gotta say, I am really liking the functionality to dollar ratio here even if there is a little assembly required. Nice!

-Dave

 

[cerving]

It's RevC. The RevA and RevB pictures are still on the web site for the benefit of the few beta testers that got those boards.

I am really intrigued! Especially with the two-fer deal!

Quick question: If I order, what revision board would I get, A,B, or C? I presume C, but have to ask...

 

[awseiger]

I'm dying over here in budapest knowing my egg timers are at home, waiting to be built...

I'm extremely excited about these, mostly the use of a simple terminal interface and the dedicated solder pads.
It seems to be the altimeter I have always wanted. I don't think I will be let down... My Dad sent me a picture, looks marvelous!

My rockets are going to have a terminal connection! I'm so excited!

 

[Derek]

what barometer are you using?

 

[cerving]

Bosch BMP-series. Same as on the Altimeter One/Two.

I have also flight tested with the Meas Spec MS5607/11, they are more expensive and there is only one distributor in the US. In flight testing with both baro sensors running simultaneously, there was almost no difference between the two in terms of noise/resolution. The MS56xx does have better temperature sensor resolution, so it does a little better job at determining compensated ASL, but it's AGL that we're after so it's "good enough". They are also both rated to about 30,000', the MS56xx has an "extended" range whose accuracy is not rated or guaranteed; some of the other altimeters using this sensor have found that it works to 100,000' with reduced accuracy. I would assume the Bosch would as well, but quite frankly I am personally very unlikely to test the limits of the sensor in a flight.

what barometer are you using?

 

[ClayD]

I have to admit.........
This product hits a soft spot for me. I never got in this hobby to shell out cash for something that I can do on my own. But, guess what, I am not an electric engineer, or as i have found out electronic theory is hard for my head to understand and i cannot do this on my own. This kit Fosters the DIY personality i have, and is IMO perfect for learning how to do this. My son says its Chip- (i guess he is using it as a new term for cool) and my wife says, "this is well documented".(my woman has binders of documentation)lol. So, we will soon see how they fare...

I would like to discuss the posibility of makin a 2m or 70cm RDF beacon that pulses at different rates depending on state.... and in a kit form. use the external channels to fire extra charges, and output a beacon RF...
a beep every 5-10 seconds at pad state.
a beep every 2 seconds on accent
a beep ever .5 seconds under decent
a beep every 1-3 seconds on landing

 

[awseiger]

I have to admit.........
This product hits a soft spot for me. I never got in this hobby to shell out cash for something that I can do on my own. But, guess what, I am not an electric engineer, or as i have found out electronic theory is hard for my head to understand and i cannot do this on my own. This kit Fosters the DIY personality i have, and is IMO perfect for learning how to do this. My son says its Chip- (i guess he is using it as a new term for cool) and my wife says, "this is well documented".(my woman has binders of documentation)lol. So, we will soon see how they fare...

I would like to discuss the posibility of makin a 2m or 70cm RDF beacon that pulses at different rates depending on state.... and in a kit form. use the external channels to fire extra charges, and output a beacon RF...
a beep every 5-10 seconds at pad state.
a beep every 2 seconds on accent
a beep ever .5 seconds under decent
a beep every 1-3 seconds on landing

I'll admit this interests me as well. If you'll look around at the Amateur radio TNC's available you may find a good way to send the real time Eggtimer data via a 70cm link. A small, cheap, dual band transceiver can be found for as low as 35 dollars.

I think the main problem with a VHF or UHF kit is that the RF section is very susceptible to errors in soldering techniques. The front end would require pre-soldering. And besides the frontend, there's not much else that goes into a tracking transmitter.

 

[cerving]

The XBee Pro radios look like a good bet, they're about $35-$40 for each end. Because they're 900 MHz or 2.4 GHz, you don't need a ham license (not that it's a big deal to get one, but it does put some people off). I agree with you the RF stuff is tough to kit, it's certainly outside my comfort zone, so you're not gonna see an Eggtimer with integrated RF unless somebody comes up with a cheap and reasonably useful RF module. It wouldn't be very hard to vary the beeps at the different flight phases if the RF module was on-board.

I'll admit this interests me as well. If you'll look around at the Amateur radio TNC's available you may find a good way to send the real time Eggtimer data via a 70cm link. A small, cheap, dual band transceiver can be found for as low as 35 dollars.

I think the main problem with a VHF or UHF kit is that the RF section is very susceptible to errors in soldering techniques. The front end would require pre-soldering. And besides the frontend, there's not much else that goes into a tracking transmitter.

 

[xenon]

Just got both of mine in the mail. Going to pick up some IC sockets tomorrow and dig out my soldering iron (if I can find it) and hopefully get them together to test out the airstart functionality with some estes motors on a LOC IV in a few weeks, then step it up at URRF with a K & a few I's.

 

[cerving]

I recommend that you do NOT socket the ICs, G forces can pop the DIP ICs right out of the sockets, especially the 8-pin optoisolators. Had it happen on some early prototypes, fortunately not DD flights. Just double-check (or triple-check) that they're pointed in the right direction, solder two opposite corners, check it again, then solder the rest of the pins. If you stick with a 15W or equivalent iron, you are extremely unlikely to damage the ICs by soldering them.

I overcooked a board in the reflow oven, it was literally black. After I cooled it down, I tested it, and dang if the baro sensor and EEPROM chip didn't work just fine. It's amazing how tough these chips are...

Just got both of mine in the mail. Going to pick up some IC sockets tomorrow and dig out my soldering iron (if I can find it) and hopefully get them together to test out the airstart functionality with some estes motors on a LOC IV in a few weeks, then step it up at URRF with a K & a few I's.

 

[Yoehahn]

Any idea when the chips will be in or ready for the outputs? thats the only think keeping me from ordering one right now

 

[xenon]

I recommend that you do NOT socket the ICs, G forces can pop the DIP ICs right out of the sockets, especially the 8-pin optoisolators. Had it happen on some early prototypes, fortunately not DD flights. Just double-check (or triple-check) that they're pointed in the right direction, solder two opposite corners, check it again, then solder the rest of the pins. If you stick with a 15W or equivalent iron, you are extremely unlikely to damage the ICs by soldering them.

I overcooked a board in the reflow oven, it was literally black. After I cooled it down, I tested it, and dang if the baro sensor and EEPROM chip didn't work just fine. It's amazing how tough these chips are...

Good point on the G forces. Now to find that soldering iron...

 

[cerving]

I have stock right now, just email your shipping info and PayPal email address to [email protected] and they'll be on their way. $40 for one kit with the data cable, $70 for TWO kits with ONE data cable, plus $3.50 for shipping.

Any idea when the chips will be in or ready for the outputs? thats the only think keeping me from ordering one right now

 

[CarVac]

I recommend that you do NOT socket the ICs, G forces can pop the DIP ICs right out of the sockets, especially the 8-pin optoisolators. Had it happen on some early prototypes, fortunately not DD flights. Just double-check (or triple-check) that they're pointed in the right direction, solder two opposite corners, check it again, then solder the rest of the pins. If you stick with a 15W or equivalent iron, you are extremely unlikely to damage the ICs by soldering them.

I overcooked a board in the reflow oven, it was literally black. After I cooled it down, I tested it, and dang if the baro sensor and EEPROM chip didn't work just fine. It's amazing how tough these chips are...

It definitely depends on the IC socket. My tailcone rocket data logger has its op-amps in sockets because I put them in there at one point and they refused to come out: I bent a chip puller trying.

 

[markjos]

I just built my eggtimer yesterday - it arrived while I was at USLI, and I finally got around to it. I've been testing it on the bench a bit, and it looks great - different, but great. Now I just need to decide the first project in which it will fly...

It's a really nice board, and thorough design. Good job!

Mark Joseph
NAR/TRA L2
Central Illinois Aerospace

 

[cerving]

Good machined-pin sockets can handle it, but unless you have a really good electronics store nearby you can't get them off the shelf. They cost more than the chips, too. G forces will definitely pop smaller ICs out of the sockets if you're using the Radio Shack stamped-pin variety; since that's what most hobbyists have ready access to, it's better just not to go there.

It definitely depends on the IC socket. My tailcone rocket data logger has its op-amps in sockets because I put them in there at one point and they refused to come out: I bent a chip puller trying.

 

[CarVac]

Good machined-pin sockets can handle it, but unless you have a really good electronics store nearby you can't get them off the shelf. They cost more than the chips, too. G forces will definitely pop smaller ICs out of the sockets if you're using the Radio Shack stamped-pin variety; since that's what most hobbyists have ready access to, it's better just not to go there.

Yeah, I don't know exactly what kind I have...I took them from my school stockroom.

 

[awseiger]

What would be the point in socketing the chips anyway? I dont see what difference it would make, really. Desoldering through hole chips is not terribly tough.

You could also wrap a zip tie around the board where the chips are to hold them in.

 

[ksaves2]

I've built three of them with little problem. I did have one with a micro solder glob I had to debug but other than that, the third one went together in two hours.
I do have a board holder for soldering purposes, light and head magnifier. I REALLY like the startup. Takes a little while but if the ET doesn't find any problem with your programming, it goes into a fluttering tone mode that says it's ready to go. If you program it for dual deploy and one channel is defective such as no battery or a poor ematch connection, you get a hi/lo warning twitter that will tell you which channel is defective. There is no mistaking the error code. I like it.
Yes, one has to come up with their own wiring stratagem as it doesn't use the ubiquitous screw terminals. Heck, you can buy the screw terminals dirt cheap and put them on a board next to the ET if you like. If one is going to do a high G flight in a really screaming meeme, they can directly hardwire (solder) the connections to the ET. I bought 100 JST connectors on ebay and since I'm not going to be doing "high stress" flights, I'm just going to plug connectors together and apply duct tape for security. Also with the optoisolators shouldn't be as much of a problem of interference from radio tracking transmitters
This is a very nice replacement for the Adept 22. $40.00 for the first one and the extra ones are a bit cheaper. Plus it's programmable and the data downloadable via computer. This is really a price breakthrough for a deployment computer. Kurt Savegnago

 

[ksaves2]

I recommend that you do NOT socket the ICs, G forces can pop the DIP ICs right out of the sockets, especially the 8-pin optoisolators. Had it happen on some early prototypes, fortunately not DD flights. Just double-check (or triple-check) that they're pointed in the right direction, solder two opposite corners, check it again, then solder the rest of the pins. If you stick with a 15W or equivalent iron, you are extremely unlikely to damage the ICs by soldering them.

I overcooked a board in the reflow oven, it was literally black. After I cooled it down, I tested it, and dang if the baro sensor and EEPROM chip didn't work just fine. It's amazing how tough these chips are...

I agree, there is no reason to use sockets with this device. What you gonna do? Use the components in another project later on?:no:

I've built three of them and all of them bench test fine. Do what cerving says above and all will be well. Go over the board with a magnifier to make sure the soldering is clean and you will be good to go.

My only caution is if you don't use a switch on the pyro battery, the circuit does draw some current even with the ET off. I found this out with bench testing and using LEDS on the ematch circuit. I didn't measure the draw but it could be a problem if you let a loaded project sit overnight or longer before firing and you use a small capacity battery. One could use 3.7V lipos if just using ematches.
Again, if one preloads a rocket before bringing to the field, depending on the time frame, the pyro battery might be in jeopardy if there is not a switch to turn the circuit off. If one preps and flies onsite, shouldn't be a problem.
Kurt Savegnago

 

[troj]

I agree, there is no reason to use sockets with this device. What you gonna do? Use the components in another project later on?

The upside is you don't have to worry about frying an IC with a soldering iron.

-Kevin

 

[Area66]

at the price the rework/soldering station are on the bay. I see no reason to use a soldering iron

https://www.ebay.com/itm/NEW-852D-2...542?pt=LH_DefaultDomain_0&hash=item4ac33b49ce

 

[accpool]

at the price the rework/soldering station are on the bay. I see no reason to use a soldering iron

https://www.ebay.com/itm/NEW-852D-2...542?pt=LH_DefaultDomain_0&hash=item4ac33b49ce

sorry for my stupidity but, how do you use a rework/soldering station?