Introducing 'AltiLogger', a new high accuracy altimeter

Leo said:

A note on this:

I have been using this method on my own built altimeters for some time. While the altitude measurements are more precise, they are still off because you are measuring temperature differences inside the ebay. If you really want precision then you need to have a temperature probe outside of the rocket and shielded from sunlight.
Also, at times I had the impression of people not really trusting my altitude readouts because they were off compared to commercial altimeters.
I have since made it possible via my UI software that one can choose to ignore or select "Ambient air temperature altitude correction". For most flights I elect to ignore this option simply for better mainstream comparisons

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Leo
This is a very nice user interface. Is it .net? Java?

It's written with Processing. Not the smartest thing to do but it works well

Leo said:

It's written with Processing. Not the smartest thing to do but it works well

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Is your software available for others to use? It looks really nice.

CarVac said:

That I would very likely buy.

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Ditto.

I am building something similar in Java for free and I should have a new version out soon
https://rocket.payload.free.fr/index.php?option=com_content&view=article&id=13&Itemid=11&lang=en
all the altimeter configuration is softcoded in the microcontroler EEPROM

Hi Guys,

I'm just giving a progress update on the development of this Altimeter for those who are interested. So the V2 prototypes have been produced and I've been adapting the firmware for the new microcontroller and hardware. So far I verified that all functions are working correctly, the board logs all sensor data (pressure, temperature, acceleration, magnetometer) that can be downloaded via USB. I have also verified the accuracy of the new crystal oscillator so all that is left to do is to finish the firmware and optimize current consumption. I also want to add firmware update capability via USB before I send units to anyone so that new features and improvements can be made with updates. I managed to route an I/O line to one of the metal plated mounting holes. I'm thinking that it should be possible to secure a wire there with a screw to deploy a parachute using an external MOSFET so that is something I might exploit at some stage.

I've put some photos of the new boards up on the project's facebook page: https://www.facebook.com/flytrak

I'm looking forward to your device when it's available as I would like to do a lot of comparison tests.

Leo said:

I'm looking forward to your device when it's available as I would like to do a lot of comparison tests.

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I should have a spare prototype I can send you soon. I just want to get firmware update via USB working first as I imagine there will be a lot of firmware changes in the next 3-6 months.

stefel said:

I should have a spare prototype I can send you soon. I just want to get firmware update via USB working first as I imagine there will be a lot of firmware changes in the next 3-6 months.

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That's fine with me

I just found about this "Electronics Etsy" through reddit. It's a website called Tindie where you can setup a shop, tailored to electronics. You can set up a fundraiser where people pledge to purchase, and as long as you get X number of orders, it rolls over into an actual purchase. I.e. if your board is 14mm and the company is enforcing that you make 64 of them at a time, you can do a "fundraiser" (pledges) to make sure you at least break even. Might be a good place to advertise?

wetmelon said:

I just found about this "Electronics Etsy" through reddit. It's a website called Tindie where you can setup a shop, tailored to electronics. You can set up a fundraiser where people pledge to purchase, and as long as you get X number of orders, it rolls over into an actual purchase. I.e. if your board is 14mm and the company is enforcing that you make 64 of them at a time, you can do a "fundraiser" (pledges) to make sure you at least break even. Might be a good place to advertise?

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Cool thanks for the tip, I'll check it out. I don't really need people to place pre-orders or anything, I just need to have a rough idea of how many people are interested, e.g. 5-10 or 50-100 and then I know approximately how many parts to order and how many boards to produce so in the meantime if anyone is interested feel free to post here, send me a PM or Like/comment on the project's facebook page.

By the way the new boards are looking sharp so far, I have not found any hardware issues, the firmware has been adapted to use the 32kHz oscillator for timing and to use the bigger 2MBit EEPROM for logging. There are a couple of firmware issues I'm trying to debug now related to accelerometer interrupt handling. Accelerometer data looks fine but there is something funny with the interrupt handling that can be seen on the oscilloscope so I have to investigate what's going on...

I hope I can launch the board on a real rocket soon...

Bump. Any update on this? Would love an accelerometer such as this to run alongside my Baro altimeters.

patelldp said:

Bump. Any update on this? Would love an accelerometer such as this to run alongside my Baro altimeters.

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I've been working on enabling firmware update capability via USB and it's taking me quite a bit longer than I expected. This is not very interesting from the rocketry side but I need to get this working before I ship any boards because I want to be able to provide fixes, improvements and added functionality through firmware updates. Basically the firmware image can be downloaded into the EEPROM of the device via USB, then a CRC check is performed and finally the bootloader reads data from the EEPROM and programs it into the flash of the microcotroller. I have all the data transfer/CRC stuff working and I'm currently working on the last step of the firmware update process (flash programming). Then I'll be making the production test jig where the boards will be programmed and tested after assembly. So getting there...

Hi everyone,

I just wanted to let you guys know that there won't be any production version of this altimeter due to lack of interest. I'll keep developing it for myself though as now there is a new variant of the barometer I'm using which more compact and uses less power and the accelerometer/magnetometer chip I've been using is being phased out by the manufacturer, so the idea now is to change the barometer and then I should have more space available to fit a higher-G accelerometer and a stand-alone magnetometer IC.

In that case, would you be willing to release the schematics to those of us who would like one for personal use?

wetmelon said:

In that case, would you be willing to release the schematics to those of us who would like one for personal use?

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I'd be happy to make it open. The problem is though, that it's not so straight forward to program the micro as there is no room for a connector to connect to a picKit (and you'll need a PICkit 3 to program the processor). Instead there are test points at certain locations of the board and a pin bed has to be made to connect to those points, to allow you to program it. I did the layout for such a board a couple of weeks ago so that I don't have to solder wires onto the test points. Also, last time I checked, for some reason Microchip don't allow you to release your source code if you use their USB stack (which I do), and at the time I did the firmware there was no other USB driver available that will work on this chip, and I didn't want to spend months making my own, I'll have to check if that changed in the meantime. I think that after the next redesign we'll see if there's enough interest with a higher-G accelerometer to do a production version?

Reviving this thread to say I'm definitely interested -- I'd like a board with higher range than an Altimiter2, but less expensive than a Raven. I want to be able to verify Mach.

Zeroignite said:

Reviving this thread to say I'm definitely interested -- I'd like a board with higher range than an Altimiter2, but less expensive than a Raven. I want to be able to verify Mach.

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There are a number of ways to verify your rocket has exceed Mach 1 that won't cost you anything.

Why makes you think a commercial version of a state-of-the art high-G IMU with deployment in low quantity production would have a retail price lower than a Raven? I can't see the OP selling it for anything less than $250 and at that price it would be a bargain.

Bob

Logging baro can tell me I busted mach, but not accurately how fast I did go. What other methods are you thinking? Sims are only as good as the design input and simulation method, and the latter often is unstable at transsonic and faster. RASPaero is a better sim but has limited design input.

Regarding cost, that's a pretty good point.

I'm not sure why you think sims go unstable at transonic velocity or higher. They don't. They may not be accurate, but this does not mean they go unstable.

To sim a flight properly, all you need is the rocket pad weight, the motor thrust curve, the aerodynamic cross-sectional area, and the Cd as a function of velocity plus the equations of motion. If you sim matches the principal flight profile features, then the velocity profile generated will be accurate.

See https://www.rocketryforum.com/showthread.php?69192-Interpreting-velocity-from-SL100-data

Bob

Poor wording on my part. I meant inaccurate