Altimeters -How big is too big?

Hi All,

Just wondering what size you all prefer your altimeter's to be? Or if it matters...
I see the existing products all range in size quite alot.

Ive had suggestions of 1" x 4" which seems about right to me.
Currently my board design is 1.25" x 5" (same size as the CPR3000 system) but im in the process of compacting it

Also, mtwieg has been working very hard to teach me about op-amp's and FET's and has been a huge help!
The op-amps are for the continuity test and allow the device to detect carbon build up on the terminals.
However, these op-amp's take up a fair amount of board space and i'm wondering whats more important to you all;

-smaller board with simple cont. test (could detect continuity incorrectly if enough carbon builds up...)

OR

-slightly larger board with funky cont. test?

Thanks for the input,

Alec

Anyone that will fit the smallest rocket you plan to do DD with. My missile works RRC2 can barely fit into a 38mm tube and others can fit pretty easy. Just get one that works is all I can say.

Originally posted by chicagonative17
Anyone that will fit the smallest rocket you plan to do DD with. My missile works RRC2 can barely fit into a 38mm tube and others can fit pretty easy. Just get one that works is all I can say.

Click to expand...

Fair enough

As well as being for personal use, I hope to make this available to other (after testing of course!) so am trying to make it fit most people needs.

Alec, have you tested the continuity tester circuit yet? I wouldn't make any impacting decisions until you know everything is going to work out.

Also, How many channels are you checking? Do you need amplification anywhere else in the device?

Originally posted by mtwieg
Alec, have you tested the continuity tester circuit yet? I wouldn't make any impacting decisions until you know everything is going to work out.

Also, How many channels are you checking? Do you need amplification anywhere else in the device?

Click to expand...

Haven't tested it just yet.

I am trying to get some through hole components to test the op-amp bit on a breadboard as I can't afford to fork out for a prototype board if it doesnt work

I will be checking 3 channels for pyro continuity.
The only other analog signals are from the MPXA4115A pressure sensor, and the ADXL78 accelerometer, but those are full 0-5v ranges so no amplification needed

I am sorting out the last few resistor values, then I may get you to look over it If thats ok of course?

EDIT: Forgot to say, if at all possible, I am going to try squeeze all the components for the fancy cont. test onto a board small enough to fit into a 24mm tube, or 38mm at the very least.
That way, if its not needed, or doesn't work I am not left without space when I remove it

Well, I love the size of my R-DAS tiny (1.1" by 3.15"), but I can use anything up to about the size of an RRC2X (1.3" by 3.6"). Too much bigger than that, and it begins to become more difficult to fit into small electronics bays.

Originally posted by cjl
Well, I love the size of my R-DAS tiny (1.1" by 3.15"), but I can use anything up to about the size of an RRC2X (1.3" by 3.6"). Too much bigger than that, and it begins to become more difficult to fit into small electronics bays.

Click to expand...

Hmmmm I can get the width down to 1.1" without too much hassle (currently 1.25"). Its the length thats proving difficult.

Im sure I could push 4" with the current setup.

But this version will just do a locator beeper and data logging (barometric altitude, 2-axis acceleration, temperature and battery voltage) without the deployments. Using some small surface mount parts, I think I can get it all (including the battery, USB interface li-ion charger, beeper and EEPROM) into a package that will fit in an 18mm tube (C-engine minimum diameter) and be under 2 inches long. But I'm not done designing yet so we'll see.

Small surface mount parts are actually pretty easy to work with, especially the SOIC size for ICs, and resistors in the 1206 size. There are several good web sites that explain how to use a toaster oven or a $20 hot plate (what I use) to re-flow solder paste that you can squirt out with a syringe, you can get custom PCBs pretty cheap ($100 for 3), and Eagle board layout software is free for hobbyists with small boards. I find that optimizing the trace layout in Eagle is a fun and addictive puzzle, but maybe I'm just weird that way.

Originally posted by basil4j
Hmmmm I can get the width down to 1.1" without too much hassle (currently 1.25"). Its the length thats proving difficult.

Im sure I could push 4" with the current setup.

Click to expand...

That would definitely be worth considering...

The nice thing about the 1.1" width is that it can fit in a 29mm tube. The extra length is easier to deal with than extra width, at least for me...

Originally posted by Adrian A
you can get custom PCBs pretty cheap ($100 for 3), and Eagle board layout software is free for hobbyists with small boards. I find that optimizing the trace layout in Eagle is a fun and addictive puzzle, but maybe I'm just weird that way.

Click to expand...

Check out batchpcb
EDIT: ^ I hope im allowed to say this?? :\

I too have that problem lol, eagle-itus

That would definitely be worth considering...

The nice thing about the 1.1" width is that it can fit in a 29mm tube. The extra length is easier to deal with than extra width, at least for me...

Click to expand...

Ok, ill definatly reduce the width then. Will see how I get on reducing the length.
This is a full recording barometric and acceleration altimeter with 3 pyro outputs. Also has USB interface which takes a bit of board space, and whats more I hope to get it low cost! (Well, Ill try )

Originally posted by basil4j
Hi All,

Just wondering what size you all prefer your altimeter's to be? Or if it matters...
I see the existing products all range in size quite alot.

Ive had suggestions of 1" x 4" which seems about right to me.
Currently my board design is 1.25" x 5" (same size as the CPR3000 system) but im in the process of compacting it

Also, mtwieg has been working very hard to teach me about op-amp's and FET's and has been a huge help!
The op-amps are for the continuity test and allow the device to detect carbon build up on the terminals.
However, these op-amp's take up a fair amount of board space and i'm wondering whats more important to you all;

-smaller board with simple cont. test (could detect continuity incorrectly if enough carbon builds up...)

OR

-slightly larger board with funky cont. test?

Thanks for the input,

Alec

Click to expand...

Go with the smaller, easier one and just watch for crbon build up. clean it off after every flight and you should be fine.

Originally posted by runandgun13
Go with the smaller, easier one and just watch for crbon build up. clean it off after every flight and you should be fine.

Click to expand...

Thanks for the input I will try to do the fancy test in the given board space, but if it gets too difficult I may have to do that...

Thing's are looking good though for small board with lots of gizmos!

Originally posted by basil4j
Ive had suggestions of 1" x 4" which seems about right to me.
Currently my board design is 1.25" x 5" (same size as the CPR3000 system) but im in the process of compacting it

Click to expand...

With or without battery? The RRC2 is a reasonable size - but you have to add a battery. The Perfect Flite HiALT is a great size but it's not very feature rich.

If it fits into a LOC 3" e-bay I'll be happy - don't forget THICKNESS - an OLSEN is a TIGHT fit in a LOC 3" ebay if you use a traditional sled mounted design.

Originally posted by uncle_vanya
With or without battery? The RRC2 is a reasonable size - but you have to add a battery. The Perfect Flite HiALT is a great size but it's not very feature rich.

If it fits into a LOC 3" e-bay I'll be happy - don't forget THICKNESS - an OLSEN is a TIGHT fit in a LOC 3" ebay if you use a traditional sled mounted design.

Click to expand...

At the moment, that size is without battery (which is to be connected via terminal blocks). However, I will be adding one of those 9V battery clips like PML use on their timers, only thing stopping me is I need to find a data sheet for the PAD sizing (I also don't know how to add components to the bottom of a board in the software i'm using, but thats easy to get around )

Thickness. The highest component would be the terminals at about 8.5mm, add the 1.6mm board and a few mm for solder connections id say 12mm max (without add-on boards, still deciding wether to stack or run 'bus cables' all over the place to allow placement anywhere)

Ok, ill definatly reduce the width then. Will see how I get on reducing the length.
This is a full recording barometric and acceleration altimeter with 3 pyro outputs. Also has USB interface which takes a bit of board space, and whats more I hope to get it low cost! (Well, Ill try )

Click to expand...

Yeah - that's what I love so much about the R-das. 4 output baro and dual axis accel, recording at 200hz for up to half an hour, complete with USB interface. I don't know how they crammed it all onto a 1.1" by 3.15" board. If you could get even close to all that functionality for significantly less than the cost of the R-DAS (currently about $280), it would definitely be a great choice.

Originally posted by cjl
Yeah - that's what I love so much about the R-das. 4 output baro and dual axis accel, recording at 200hz for up to half an hour, complete with USB interface. I don't know how they crammed it all onto a 1.1" by 3.15" board. If you could get even close to all that functionality for significantly less than the cost of the R-DAS (currently about $280), it would definitely be a great choice.

Click to expand...

So far I can get about 5minutes recording (at 100Hz) on flash memory, which is not even close to half an hour!
They must of used something other than flash memory

I am hoping to add SD card storage, which will give a minimum of...3 months recording on a 16MB card (If I do my maths right )

EDIT: Is that $280 is USD?

Yep. More specifically, 220 euros, as it is made in the Netherlands. Here is their site...

From what I can find, it has 1024kB flash...

Originally posted by cjl
Yep. More specifically, 220 euros, as it is made in the Netherlands. Here is their site...

From what I can find, it has 1024kB flash...

Click to expand...

Wow! Thats about $500NZD! Shouldn't be hard to beat that then considering my target is $150NDZ or there abouts...

Wow - for the features that you want to put in it, that's a really good price...

Originally posted by cjl
Wow - for the features that you want to put in it, that's a really good price...

Click to expand...

Lets just hope I can stick to that lol.

I'm getting quote at the moment and just finalising a few things with the hardware (E.g. SD Card, battery holder and size)

Just realised you said it had 1024k memory! its amazing they cram so much data in!

Hmmm, I think I may have to look at what im saving lol

Have you considered something like the atmel dataflash? These devices are quite small and cheap, but they provide plenty of storage. The AT45DB161D costs less than 3$, but provides 16Mbit, more than every altimeter that I know (not counting the compact flash card in the gwiz DCS)

Reinhard

Hmmmm looks interesting.

I think for now Ill stick with the memory I am using as it is i2c and using the same bus as my program memory. Makes it alot easier to squeeze it all on the board

The memory can handle 4 mins storage total, which will all be transfered to the SD card a the end of the flight if SD card is installed.

Otherwise, the data is just left on the flash memory. I will look info adding that memory as a memory module maybe

Thanks,

Alec

EDIT: I take that back! After looking at my schematic, turns out I have enough spare IO on the MCU to deal with the extra SPI bus and whats more, its easier to route!

Brilliant Will design it in and figure out how to use it!

Originally posted by basil4j
Hmmmm looks interesting.

I think for now Ill stick with the memory I am using as it is i2c and using the same bus as my program memory. Makes it alot easier to squeeze it all on the board

The memory can handle 4 mins storage total, which will all be transfered to the SD card a the end of the flight if SD card is installed.

Otherwise, the data is just left on the flash memory. I will look info adding that memory as a memory module maybe

Thanks,

Alec

EDIT: I take that back! After looking at my schematic, turns out I have enough spare IO on the MCU to deal with the extra SPI bus and whats more, its easier to route!

Brilliant Will design it in and figure out how to use it!

Click to expand...

I have a 4gb SD card and a 512MB. Why not make it so you can use an extra one if you want? I think 4min of memory is low. I would go for 15-20min. By the time you click it on at the away p ad an launch it 10-15 min can go by.

Ben

Ben

Oh, I should probably explain a bit more.

The pre-launch data will be held in a 1 second (time to be confirmed) circular buffer which will be constantly refreshed prior to launch.
Once launch is detected, that 1 seconds will be trasnfered the the main memory and all further data recorded after it.

That way, 1 seconds of data will be recorded prior to launch to save memory, and also acommodate and delays in launch detection (which is when data logging of the flight begins normally)

I may extend this 1 second is needed.

About SD cards. I think 1 SD card is al that is needed To give you an idea of how much you can store on your 4GB card...

5 bytes data per 10ms = 500 bytes per second
There are 4294967296 bytes in 4GB which means you can record 8589934 seconds of data.
8589934 seconds = 143165 minutes = 2386 hours = 99 days= 3 months constant flying...thats a whole lot of 3 miunte flights

Now there may be some mistake in my calculations, but I can't be too far off

Originally posted by ben
I have a 4gb SD card and a 512MB. Why not make it so you can use an extra one if you want? I think 4min of memory is low. I would go for 15-20min. By the time you click it on at the away p ad an launch it 10-15 min can go by.

Ben

Ben

Click to expand...

Uhh, ben...

Recording alts don't start recording until they detect liftoff...

Originally posted by cjl
Uhh, ben...

Recording alts don't start recording until they detect liftoff...

Click to expand...

whoops I am thinking of video. But still I think 4min is a little short

Ben

Originally posted by basil4j
Oh, I should probably explain a bit more.

The pre-launch data will be held in a 1 second (time to be confirmed) circular buffer which will be constantly refreshed prior to launch.
Once launch is detected, that 1 seconds will be trasnfered the the main memory and all further data recorded after it.

That way, 1 seconds of data will be recorded prior to launch to save memory, and also acommodate and delays in launch detection (which is when data logging of the flight begins normally)

I may extend this 1 second is needed.

About SD cards. I think 1 SD card is al that is needed To give you an idea of how much you can store on your 4GB card...

5 bytes data per 10ms = 500 bytes per second
There are 4294967296 bytes in 4GB which means you can record 8589934 seconds of data.
8589934 seconds = 143165 minutes = 2386 hours = 99 days= 3 months constant flying...thats a whole lot of 3 miunte flights

Now there may be some mistake in my calculations, but I can't be too far off

Click to expand...

I am an avid flyer What about going to pluto! Can't forget pluto

Ben

Good news, I am designing in the 16MBit memory which Reinhard suggested

As well as extra memory, it is also simplifying board layout!

Should get about 64 minutes recording out of this one

Originally posted by ben
I am an avid flyer What about going to pluto! Can't forget pluto

Ben

Click to expand...