I'm doing some testing on parachutes and want to record descent rate.   Is there a way to do this with say, a cube, without going to a pitot tube? I would think that the angular descent of a parachute would not give accurate descent rate (or would it?) due to the lateral motion.   Does the cube have an RTC to record the samples by time along with the other sensors, so I could calculate speed over time?  How about an add-on to a cube (a la arduino shield) to do the airspeed descent rate.   I'm comparing designs and sizes of chutes.  Would like as accurate of info as is cost effective. I'd want to log it onboard, to negate the need for telemetry.

Thanks

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If you're willing to connect a Raspberry Pi to the Telem2 port and read the MAVLink messages using dronekit (this requires a little programming), then you can record the changing pressure vs. time, which will give a pretty accurate descent rate with some minor calculations.  More accurate than the GPS altitude in this particular application, in my opinion.

Thanks for the info.  I do have a Pi3.   May do that.  I'd have to figure out the programming.

I was wanting a small size solution.  THe Pi may be too big.

The barometer will give you that data. Ensure you have GPS for the timing... the gps will also give you that data.

all you need to do is look at the logs.... read the alt vs the time line.

But rather than trying to measure decent 'rates' all that is really important is the final Z vib  (and x and y to a lesser degree) shock value as it hits the ground!

ptegler

you could easily do this with an arduino [nano/micro/whatever] + SD reader + MPL3115A2. If you wanted to also beam down the data in realtime you could also use a set of radios. Total cost [if buying from ebay] would be about 10 bucks. [20ish if you wanted to use a couple of radios as well] if you needed accurate time measurememt you could also just add a RTC module as well.

BMP280 https://www.ebay.com/itm/BMP280-3-3-Barometric-Pressure-Altitude-Se...
4.00

DS1302 Clock https://www.ebay.com/itm/DS1302-Clock-Module-with-Battery-Real-Time...
1.00

SPI Reader Micro SD Memory Card https://www.ebay.com/itm/SPI-Reader-Micro-SD-Memory-Card-TF-Memory-...
1.00

Arduino nano https://www.ebay.com/itm/Nano-V3-0-Mini-USB-ATmega328-5V-16M-Micro-...
4.50

Radio Link https://www.ebay.com/itm/2pcs-433Mhz-Radio-Link-RF-transmitter-Rece...
6.00

Thank you all !  This is good info.   As I'm reading these, I'm watching a vid of Limor Fried.  hehe.. Thank you again!

Thanks for the specifics.  I'm using circuit.io for wiring diagram.   They don't have the radio link, though, so how should I wire it, and what do I need on the ground for it?

Craig said:

you could easily do this with an arduino [nano/micro/whatever] + SD reader + MPL3115A2. If you wanted to also beam down the data in realtime you could also use a set of radios. Total cost [if buying from ebay] would be about 10 bucks. [20ish if you wanted to use a couple of radios as well] if you needed accurate time measurememt you could also just add a RTC module as well.

BMP280 https://www.ebay.com/itm/BMP280-3-3-Barometric-Pressure-Altitude-Se...
4.00

DS1302 Clock https://www.ebay.com/itm/DS1302-Clock-Module-with-Battery-Real-Time...
1.00

SPI Reader Micro SD Memory Card https://www.ebay.com/itm/SPI-Reader-Micro-SD-Memory-Card-TF-Memory-...
1.00

Arduino nano https://www.ebay.com/itm/Nano-V3-0-Mini-USB-ATmega328-5V-16M-Micro-...
4.50

Radio Link https://www.ebay.com/itm/2pcs-433Mhz-Radio-Link-RF-transmitter-Rece...
6.00



Ken Wilkins said:

Thanks for the specifics.  I'm using circuit.io for wiring diagram.   They don't have the radio link, though, so how should I wire it, and what do I need on the ground for it?

Personally I'd just use a set of 3DR Radios. the air unit would connect to the RX/TX/VCC/Gnd  on the arduino and the ground unit would be just a standard USB connect. For anything other than windows you would probably need an OTG cable but the range would be nice :)

Then you would just use serial1.write to beam out the info to the ground unit.

"or" you could just use those radios [same hookup for the air unit] and another arduino for the ground unit and you could just use anything from arduino ide's serial monitor or any other terminal to connect to the usb port. You could get fancy and use Processing  and make graphs and stuff :)



Craig said:

Personally I'd just use a set of 3DR Radios. the air unit would connect to the RX/TX/VCC/Gnd  on the arduino and the ground unit would be just a standard USB connect. For anything other than windows you would probably need an OTG cable but the range would be nice :)

Then you would just use serial1.write to beam out the info to the ground unit.

"or" you could just use those radios [same hookup for the air unit] and another arduino for the ground unit and you could just use anything from arduino ide's serial monitor or any other terminal to connect to the usb port. You could get fancy and use Processing  and make graphs and stuff :)

you could also get real fancy and add a cheap gps unit as well :)

https://www.ebay.com/itm/NEO-6M-GPS-Module-Aircraft-Flight-Controll...

I ordered that equipment.    Having a time finding a 5v lipo (flat).  

Craig said:

you could easily do this with an arduino [nano/micro/whatever] + SD reader + MPL3115A2. If you wanted to also beam down the data in realtime you could also use a set of radios. Total cost [if buying from ebay] would be about 10 bucks. [20ish if you wanted to use a couple of radios as well] if you needed accurate time measurememt you could also just add a RTC module as well.

BMP280 https://www.ebay.com/itm/BMP280-3-3-Barometric-Pressure-Altitude-Se...
4.00

DS1302 Clock https://www.ebay.com/itm/DS1302-Clock-Module-with-Battery-Real-Time...
1.00

SPI Reader Micro SD Memory Card https://www.ebay.com/itm/SPI-Reader-Micro-SD-Memory-Card-TF-Memory-...
1.00

Arduino nano https://www.ebay.com/itm/Nano-V3-0-Mini-USB-ATmega328-5V-16M-Micro-...
4.50

Radio Link https://www.ebay.com/itm/2pcs-433Mhz-Radio-Link-RF-transmitter-Rece...
6.00

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