The Eggfinder - A Low-Cost GPS/RF Tracking System

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Cris,

Will your unit have onboard memory to record the GPS time/position data throughout the flight ?
 
It does not, but you can record the transmitted location information on your ground station. The primary purpose of the Eggfinder is to help you recover your rocket, so the main thing that you need is the last GPS location... the ones in-between launch and landing are nice but not essential.

Cris,

Will your unit have onboard memory to record the GPS time/position data throughout the flight ?
 
One of these was flown at the Phoenix site right? How high did it fly and was successfully recovered?
 
It will be sold ONLY as a kit, due to the vaguaries of FCC regulations. If you want to pay someone else to put it together, you may, but they CAN NOT purchase the kits and sell the BUILT to you. YOU have to purchase the kit and have THEM build it.

Will a built / no soldering required version be available, or just a kit?
 
It flew twice at TRAPHX, to about 6400' and 8300'. They landed about 1/2 and 2/3 mile away, respectively. Got good data on both, the Formula 98 (K645, 6400') had the tracker fall off the shock cord, probably at main deployment judging from the data. We got both the rocket and the Eggfinder back. The GL Escape Velocity (J420, 8300') tracked from shortly before apogee all the way to the ground, we saw it in the sagebrush before we actually got to the GPS landing coordinates, which were within about 2' of the Eggfinder in the nose cone.

One of these was flown at the Phoenix site right? How high did it fly and was successfully recovered?
 
It will be sold ONLY as a kit, due to the vaguaries of FCC regulations. If you want to pay someone else to put it together, you may, but they CAN NOT purchase the kits and sell the BUILT to you. YOU have to purchase the kit and have THEM build it.

Can a 90% complete version be made legally and sold?
 
Nope.

I touched on this earlier in the thread, the FCC has a general exemption from its certification regulations FOR THE PRODUCER OF A KIT. Look at Spark Fun, Ramsey, etc., you will see that NONE of the kits that are offered have been through FCC certification; they don't need to be. If someone buys them and sells them partly or fully assembled, however, then that person is considered to be a "marketer" of an FCC-regulated product, and THEY have to submit the assembled product to the FCC for certification. It costs about $10,000-$15,000.

There has been at least one FCC action against somebody who actually did this; the FCC slapped their wrist gently and told them they couldn't do that; from what I can tell, the guy was simply trying to make it easier on people who didn't have the skills to assemble the kit (which is what I think you are going after), so he was doing it for them as a turnkey service. Last time I checked, he's still assembling the kits, but he's making the end users purchase them; offering a kit assembly service is certainly a legal business.

Like I say in the docs and on my web site, I'm not gonna lie... an Eggfinder requires previous soldering/kit-building experience. If you've successfully built an Eggtimer (or two or three...) then you probably won't have any trouble with it. If your experience with a soldering iron is limited to tinning wires, then it may not be for you. I'm a pretty old guy, and my eyes and coordination aren't the best, and of course I've built quite a few of them. The passive parts are all through-hole, and the few SMT parts are all large-pitch (at least .050"), and I include special .020" low-temperature solder, so it really isn't terribly difficult.

Can a 90% complete version be made legally and sold?
 
Receivers are a little different than transmitters, the FCC doesn't require as much of them since they theoretically shouldn't be broadcasting a signal. They only want to make sure that it's not an "unintentional radiator", i.e. that it doesn't interfere with other things. This came into being in the early 80's, when some of the home computers and video games that hooked up to TVs leaked a lot of RF, and would mess up your neighbor's TV. The original Apple II was one of the worst offenders.

Ask around your club, I bet you can find somebody that would do it for you.
 
It runs on 3.3V, that's a little too low for a 1S LiPo with a regulator. That's why I recommend a 2S. I'm specifying a 4.5V minimum.
I assume that's a linear voltage regulator? So if we wanted to run it off 1-cell LiPo could we bypass or leave out the regulator?

I'm thinking once I go timer+finder I'll probably want one power supply, low-current ignitors, and maybe a buffer cap for anti-brownout.
 
I haven't tried it because the spec for the GPS is 3.6V maximum. It would probably be OK on a 1S LiPo, but I haven't tried it... maybe I'll do it with an older one to see what it does.

I assume that's a linear voltage regulator? So if we wanted to run it off 1-cell LiPo could we bypass or leave out the regulator?

I'm thinking once I go timer+finder I'll probably want one power supply, low-current ignitors, and maybe a buffer cap for anti-brownout.
 
I haven't tried it because the spec for the GPS is 3.6V maximum. It would probably be OK on a 1S LiPo, but I haven't tried it... maybe I'll do it with an older one to see what it does.
Thanks. There's almost certainly a good way to make it work within spec, but it's hard for me to guess without having part specs and at least a partial circuit diagram.
 
Thanks. There's almost certainly a good way to make it work within spec
You use a low-dropout linear regulator that can go from 1S voltage to 3.3V. Typical 1S cells are above 3.5V until they are pretty close to empty. Derek's GPS tracker does this, for example.
 
Yes, but the very-low dropout regulators cost signficantly more, and don't handle as much current. For example, look up the price of the LM1117MPX-3.3 (DO ~ 1V, 800 mA) vs a LT1763 (DO ~ .3V, 500 mA). Adding $3-$5 for the regulator doesn't add much bang for buck in this case, except for being able to use a slightly smaller battery. There are plenty of 2S LiPo's out there cheap, i.e. from Hobby King. The weight saving is very small, under 20g, going from 2S to 1S at 300 mAH. 20g is an insignificant amount of weight in any rocket that would be using an Eggfinder.

And that is also why I added a regulator to the Eggtimer... I got a lot of requests for it from people who were used to using 9V or 2S LiPo batteries.

You use a low-dropout linear regulator that can go from 1S voltage to 3.3V. Typical 1S cells are above 3.5V until they are pretty close to empty. Derek's GPS tracker does this, for example.
 
Yes, but the very-low dropout regulators cost signficantly more, and don't handle as much current. For example, look up the price of the LM1117MPX-3.3 (DO ~ 1V, 800 mA) vs a LT1763 (DO ~ .3V, 500 mA). Adding $3-$5 for the regulator doesn't add much bang for buck in this case, except for being able to use a slightly smaller battery. There are plenty of 2S LiPo's out there cheap, i.e. from Hobby King. The weight saving is very small, under 20g, going from 2S to 1S at 300 mAH. 20g is an insignificant amount of weight in any rocket that would be using an Eggfinder.

And that is also why I added a regulator to the Eggtimer... I got a lot of requests for it from people who were used to using 9V or 2S LiPo batteries.
Completely fair :) I'm just one of those folks who is a little zealous about optimization.
 
You use a low-dropout linear regulator that can go from 1S voltage to 3.3V. Typical 1S cells are above 3.5V until they are pretty close to empty. Derek's GPS tracker does this, for example.
OTOH, a 2cell lipo would exceed Derek's trackers regulator Vin spec.
 
FYI, I'm going to start taking orders on the Eggfinder, I need to get an idea of how many I will need to kit up in the first batch and also if I need to order more parts. I expect to be ready to ship in about a week. Those of you who have already sent me your order information will get first priority. The usual procedure...

1) Send an email with what you want along with your PayPal-linked email address and the shipping address to
[email protected]
2) I'll create an invoice and send it back to you for payment via PayPal when I have the product ready to ship (I don't take money ahead of time... it's a bad business practice)
3) You pay the invoice, and I ship.

Prices for the Eggfinder are:
o $90 for the Starter Set (transmitter and receiver kits)
o $70 for an extra transmitter kit alone
o $25 for an extra receiver kit alone
o $3 each for the optional RP-SMA connectors
o Add $5 per order for shipping

Note that the first batch will probably all be on the default 915 MHz center frequency, at some point in the near future I will be shipping them on different frequencies (probably from 909 MHz - 925 MHz in 2 MHz increments) so you don't run into any frequency conflicts on the flying field, but it's so new that this is probably not going to be an issue for a little while.

Thanks for all your interest!

Cris Erving
Eggtimer Rocketry
 
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FYI, I'm going to start taking orders on the Eggfinder, I need to get an idea of how many I will need to kit up in the first batch and also if I need to order more parts. I expect to be ready to ship in about a week. Those of you who have already sent me your order information will get first priority. The usual procedure...

1) Send an email with what you want along with your PayPal-linked email address and the shipping address to
[email protected]
2) I'll create an invoice and send it back to you for payment via PayPal when I have the product ready to ship (I don't take money ahead of time... it's a bad business practice)
3) You pay the invoice, and I ship.

Prices for the Eggfinder are:
o $90 for the Starter Set (transmitter and receiver kits)
o $70 for an extra transmitter kit alone
o $25 for an extra receiver kit alone
o $3 each for the optional RP-SMA connectors
o Add $5 per order for shipping

Note that the first batch will probably all be on the default 915 MHz center frequency, at some point in the near future I will be shipping them on different frequencies (probably from 909 MHz - 925 MHz in 2 MHz increments) so you don't run into any frequency conflicts on the flying field, but it's so new that this is probably not going to be an issue for a little while.

Thanks for all your interest!

Cris Erving
Eggtimer Rocketry

Will there be a way to reconfigure the frequencies?
 
No, they'll be pre-set. When I start shipping them with reconfigured frequencies, you'll simply specify what frequency you want, or I'll give you one at random. It's like the old FM R/C radios used to be...

Will there be a way to reconfigure the frequencies?
 
Email sent.
You might need to adjust frequencies sooner than planned. As you know I fly at the TRA/PHX launches with Juan and the ROC launches in Lucerne, CA. I think you are gonna have some customers there too. Might need to record who gets what to prevent conflicts.
 
Email sent.
You might need to adjust frequencies sooner than planned. As you know I fly at the TRA/PHX launches with Juan and the ROC launches in Lucerne, CA. I think you are gonna have some customers there too. Might need to record who gets what to prevent conflicts.

I also want to fly one at TRAPHX.
 
everyone will be happy with the lay out . its very small and fits well into a rocket . I have one that fits into a nosecone with a battery . inside a 2" coupler with an attachment point for the bulk head through the middle . and there is still room . flying at thunder struck to 10-11k hope to someone take it to our limit of wavier thanks chris
 
Your prices look really good. Those hoperf modules are a lot less than expensive than the digi modules.

I don't get why you can't change the frequencies on the fly, though. The fw that 3dr provides allows you to do this. Are you using different firmware?
 
I'm using Hope RF's firmware. 3DR is the one that changes it. The Hope RF firmware allows you to reprogram the frequency and a few other parameters, but you need a MCU connected to a few other pins and you need to have a bidirectional serial connection to the module. The Eggfinder isn't that smart... it just takes serial data from the GPS and spits it out over the RF link. The goal was to make this a turnkey unit, no programming or futzing around required.
 
Ok, that makes sense, sort of. The 3dr fw allows you to change the freq over the air, so you don't need to plug anything into the tx - just run their sw on the pc.

Their sw is the only thing other than price that I really like about the 3dr (or hoperf) radios vs. the xbee stuff.
 
It's easy enough to tell if someone is on your frequency, plug in the receiver and see if the lights blink. I doubt that this will ever get to the level of having an transmitter impound and frequency clips like we used to do at R/C fields... I haven't even shipped any yet!
 
FYI, I'm going to start taking orders on the Eggfinder, I need to get an idea of how many I will need to kit up in the first batch

I really want one. Have you still got an embargo on the Antipodes?
 
LOL...

I have not had a chance to get my hands around the Australian regulations yet, other than to find out that they are similar to Canada but with some tighter frequency allocations because you have cell phones on the lower 900 MHz band up to 915 MHz. Assuming that there are no import issues, I will providing them on frequencies that are in compliance with Australian regulations, but it will probably be at least a month.

I really want one. Have you still got an embargo on the Antipodes?
 
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