The Eggtimer Quasar - A WiFi-enabled GPS/Altimeter

[MProcket]

How does the OpenLog module fit on the board? From the top, it looks like it would get blocked by the rectifier, or else have to sit on top of the GPS patch antenna, hindering its signal. Is there enough room for it to clear the drivers on the bottom?

 

[cerving]

I'm going to add something about that "soon" in the manual, you can either use a cable or you can bend the rectifier down 90 degrees when you mount it and the OpenLog will clear it.

 

[Crayok]

The 900 MHz transmitter is compatible with the current Eggtimer GPS receiver equipment.

I finally figured out what you meant here, I'm slow. Yes compatible in two forms, it is a low power transmitter and a 90 degree orientation from TX antenna and the GPS receive (adds a few dB isolation). My comments where around student built devices using, for example, an RFD900 (1 watt, +30dB). GPS filtering seem to have very good SAW filters on the current crop, to drop anything out of the GPS band by 60-70dB.
dB

 

[gsjames]

Mine is done. Everything checks out perfectly. I plan to use it in my Level 2 qual bird. Thanks, Cris

 

[pwrwgnwalt]

Yippee! Built my first Eggtimer items and all seem to working as intended.
Haven’t gone out into the sub-zero weather to do any testing, but around the house (indoors)
the telemetry appears to work perfectly, as does the voice module.

The builds were straightforward, following the explicit & good series of instructions Cris provides.
I did remote-mount the earphone jack on the right side of the case, and added (in the upper space
indicated inside the case) a small piece of 6mm (1/4”) fiber optic cable to enhance the LED readability.
I may, or may not, simplify the LiPo battery charging leads hanging out of the left side of the case.
The only thing I had to adjust was the LCD display dashpot - the readout first showed as very dark boxes,
barely readable at an acute angle. A small clockwise tweak of the dashpot provided a clear and easily
readable display (even in bright, direct sunlight) without any backlighting.

LCD-GPS (in the yellow Black Aero Pro v3 case)
Voice Module (below the LCD & GPS in the case)
Quasar (picture from when it was almost completed)

 

[DarthMuffin]

It works! Boy was that rough fitting it, a battery, and a threaded rod in a 1.5" bay. Rod had to be off-center a little.

 

[John Kemker]

Just received mine in the mail! Yippee!

Mine has the 70cm transmitter module, but the antenna looks to be tuned for 900MHz. Did I get the correct antenna?

 

[Simon Auty]

Quasar assembly finished and powered on for first time

 

[Simon Auty]

Testing Quasar

 

[mtnmanak]

This may have been answered somewhere else, but what is the best setting for the LCD receiver when using the Quasar so I get telemetry and GPS data? I looked in the manuals, but couldn't find anything (may have missed it). In the first post of this thread, Cris notes the LCD thinks the Quasar is a TRS, but that it can be set to the Mini/TX setting to avoid the long wait time of the TRS. But, if I set it to Mini/TX, that won't pull telemetry, correct? So, should I use Quantum or Proton instead?

 

[cerving]

This may have been answered somewhere else, but what is the best setting for the LCD receiver when using the Quasar so I get telemetry and GPS data? I looked in the manuals, but couldn't find anything (may have missed it). In the first post of this thread, Cris notes the LCD thinks the Quasar is a TRS, but that it can be set to the Mini/TX setting to avoid the long wait time of the TRS. But, if I set it to Mini/TX, that won't pull telemetry, correct? So, should I use Quantum or Proton instead?

Use the TX/Mini setting. The Quasar sends out TRS-formatted telemetry, which the GPS routines can pick up. DO NOT use the altimeter device settings, they won't decode GPS location or the TRS telemetry. You could also use the TRS or the default (TX/Mini/TRS) setting, but you'd have to wait for the TRS pairing timeout... since the Quasar doesn't pair with the LCD receiver like the TRS did, it's just a waste of your time.

 

[rAUM]

Answers to your questions...

1) The standard COCOM altitude limit is 18 km, with a 515 m/s and 4G accel limit. That's why you lose GPS data at boost... pretty much the same with all non-military GPS's. The GPS has a "balloon mode" that will go up to 80 km, with reduced accel/velocity limits... we intend to make that a settings option at some point in the future, you'll be trading off increased altitude limit for reduced sampling rate (like once maybe every 5 or 10 seconds instead of 20x/second.)

2) Like all Eggtimer products, you need a separate receiver for each transmitter. However, like the TRS, the GPS and altimeter telemetry are integrated so you only need a single receiver for both types of data. We intend to expand the telemetry that you can get out of a Quasar... real-time apogee comes to mind (you don't get that on a TRS). That will require some LCD firmware changes, our goal in the initial release was to replicate what the TRS did since the TRS is now EOL, so we didn't want to have to make you update the LCD firmware too.

3) The 70cm version looks identical... the antenna is the same form factor, except with a different color stripe (it's red instead of yellow). Ditto for the 869 MHz EU/UK version... the stripe is teal.

4) We're calling the build a 5 out of 5, based on our Focus Group. The build is similar to a Proton. All the itsy bitsy parts are on the bottom side.

A bit late, but lets say that till 30km (100k feet) you use a barometer, what would happen between the 30km and 80km altitude? Do I only get signals near apogee when the speed is lower? How would an ejection charge work then?

 

[cerving]

It sounds like you're considering the Quasar for an 80K shot...

The baro will work up until the pressure falls below the single-bit resolution of the sensor, at which point the pressure will read zero from that point on. That's at about 38 km, however the difference between a sensor reading of "1" and "2" is almost a km at that altitude... pressure altitude is very non-linear at low pressures. The resolution of the sensor at 30 km translates to a pressure altitude difference of about 40 meters, so if you're still moving at 30 km the baro should still be able to detect apogee reasonably if it occurs at that point.

Regarding the radio, you'll get data up until the range of the radio... which is dependent on a lot of things, but is probably not going to be 30 km. I have had reports of Eggfinders working to about 15 km in rockets, and 20 km in balloons (which move slowly so there's no Doppler shift or velocity lockouts). A more realistic range is about 10 km.

I'm going to add that the Quasar (and Eggtimer products in general) are not designed nor are they recommended for space shots. Very few hobbyists will every exceed the 10 km range of our radios... nevermind going to space. Our target audience is the thousands of hobbyists who launch at local sites to a few km... if you want to go to space, there are other products that are better suited for that task. Be prepared to pay a lot more... but going to space isn't cheap anyway.

 

[rAUM]

It sounds like you're considering the Quasar for an 80K shot...

The baro will work up until the pressure falls below the single-bit resolution of the sensor, at which point the pressure will read zero from that point on. That's at about 38 km, however the difference between a sensor reading of "1" and "2" is almost a km at that altitude... pressure altitude is very non-linear at low pressures. The resolution of the sensor at 30 km translates to a pressure altitude difference of about 40 meters, so if you're still moving at 30 km the baro should still be able to detect apogee reasonably if it occurs at that point.

Regarding the radio, you'll get data up until the range of the radio... which is dependent on a lot of things, but is probably not going to be 30 km. I have had reports of Eggfinders working to about 15 km in rockets, and 20 km in balloons (which move slowly so there's no Doppler shift or velocity lockouts). A more realistic range is about 10 km.

I'm going to add that the Quasar (and Eggtimer products in general) are not designed nor are they recommended for space shots. Very few hobbyists will every exceed the 10 km range of our radios... nevermind going to space. Our target audience is the thousands of hobbyists who launch at local sites to a few km... if you want to go to space, there are other products that are better suited for that task. Be prepared to pay a lot more... but going to space isn't cheap anyway.

Yeah I figured that much,KATE for example (great, but a pretty penny). So I was thinking about using a ms5611, which roughly measures till the altitude you mentioned, but what after? An accelerometer (ADXL375) should be able to measure till space, but I heard that they may become less reliable over extended flight times. That leaves me with the gps, which doesn't work (limits) at mach 3/4. Any solution?

 

[cerving]

Yeah I figured that much,KATE for example (great, but a pretty penny). So I was thinking about using a ms5611, which roughly measures till the altitude you mentioned, but what after? An accelerometer (ADXL375) should be able to measure till space, but I heard that they may become less reliable over extended flight times. That leaves me with the gps, which doesn't work (limits) at mach 3/4. Any solution?

If you're going to space, get a Kate... he's using an unlocked GPS with a really good antenna to determine apogee and trigger high-altitude events. The problem with accelerometers is that you can either have range or resolution... you can't get both. That's why most of the altimeters with high-G accels also have a low-G accel on board, then it becomes a matter of sensor fusion, and maintaining accuracy between multiple sensors can be a non-trivial problem. You'll also need a gyro, so you're looking at three sensors to deal with, at least. Better to let somebody who's done it already work that out for you. You're going to have enough problems just getting to 80K... including figuring out how to pay for it.

 

[rAUM]

If you're going to space, get a Kate... he's using an unlocked GPS with a really good antenna to determine apogee and trigger high-altitude events. The problem with accelerometers is that you can either have range or resolution... you can't get both. That's why most of the altimeters with high-G accels also have a low-G accel on board, then it becomes a matter of sensor fusion, and maintaining accuracy between multiple sensors can be a non-trivial problem. You'll also need a gyro, so you're looking at three sensors to deal with, at least. Better to let somebody who's done it already work that out for you. You're going to have enough problems just getting to 80K... including figuring out how to pay for it.

You are right, the issue is that Kate is utilizing a frequency band that is not permitted under European regulations.

 

[cerving]

I've received a lot of feedback that the manual is not clear about how/when GPS data is sent out from the Quasar to the LCD receiver. Re-reading the manual, I understand the concern, so I have added a section in the User's Guide that explains how/when GPS data is sent out to the LCD receiver compared to the TX and Mini GPS transmitters. If you have not flown your Quasar yet (or if you haven't built it...), I recommend that you download and read the latest version of the manual... that should clear up a lot of confusion about how the GPS data is sent out.

 

[Chris in Idaho]

Is wifi the only method to arm the altimeter or is there a provision to do it manually?

 

[cerving]

You can set it to auto-arm on power-up just like the other WiFI-enabled altimeters. It's a settings option... the default is to arm remotely.

 

[pwrwgnwalt]

Is wifi the only method to arm the altimeter or is there a provision to do it manually?

Chris, if you’re like we are in Montana and your launch site is remote (no cell service), know that the WiFi arming by cell phone works great.
It is a direct phone-to-altimeter WiFi connection that does not require cell service, internet, etc. out at the launch site to set and arm the altimeter, should you choose to do it by Wifi.

 

[Chris in Idaho]

You can set it to auto-arm on power-up just like the other WiFI-enabled altimeters. It's a settings option... the default is to arm remotely.

Perfect, thank you.

Chris, if you’re like we are in Montana and your launch site is remote (no cell service), know that the WiFi arming by cell phone works great.
It is a direct phone-to-altimeter WiFi connection that does not require cell service, internet, etc. out at the launch site to set and arm the altimeter, should you choose to do it by Wifi.

Good to know, but I was more wondering if I could still launch if my phone got dropped or battery ran out. Sounds like I'm good to go.

 

[Chris in Idaho]

Cris, on your website it tells me if I put the Quasar in an av bay next to steel all threads it will reduce the signal strength but (I'm paraphrasing) not enough to cause issue for 99% of situations.
Then for the mini GPS transmitter it clearly says not to run it in an av bay next to all thread and an altimeter.
Is there a difference in the way these two gadgets are affected by the metal, or do all of these comments apply equally to both products?

 

[KenECoyote]

The only thing I had to adjust was the LCD display dashpot - the readout first showed as very dark boxes,
barely readable at an acute angle. A small clockwise tweak of the dashpot provided a clear and easily
readable display (even in bright, direct sunlight) without any backlighting.

Hi, where is the dashpot? Mine is also too blocked out to see when I use anything over 1s/6v.

Also I'm loving the Quasar!

 

[rokit]

Hi, where is the dashpot? Mine is also too blocked out to see when I use anything over 1s/6v.

Also I'm loving the Quasar!

It's the potentiometer. The assembly manual shows it better than I can describe it.