Suggestion for the next Open Propeller Project
WBA Consulting
Posts: 2,934
After seeing this thread posted, I was thinking that a STEM compliant Rocket Payload Control Board would be an excellent Open Propeller Project. Thoughts from anyone?
http://forums.parallax.com/showthread.php/155368-Rocket-Payload-for-STEM
http://forums.parallax.com/showthread.php/155368-Rocket-Payload-for-STEM
Comments
That sounds like is along the line of a Hoverfy platform.
Might just fit in nicely.
My thoughts were:
- Standard Propeller setup in ~3"x4" formfactor
- USB
- Dual 64k EEPROMs
- micro SD socket
- ADC
- 3 axis gyro/accel
- temperature
- humidity?
- pressure
- expansion port
Not sure what else is typical for rocket telemetry.I'm not sure how closely the sensor needs of a quadcopter and the sensor needs of a rocket align.
I also wonder about a uSD socket in a rocket. I'd be concerned about vibrations causing intermittent breaks with the contacts on the card and the brushes/fingers in the socket. I'd think some sort of flash chip would be safer.
I do think a rocket data logger would be fun.
I agree that there is a difference between quadcopter and rocketry needs, but what could be made for rocketry could work for many other things. Essentially, it would be a versatile datalogger.
The uSD could be used in the rocket with appropriate risk mitigation, but my intent was more for offloading logged data with having to connect a PC to the board directly. Also, for other datalogging applications, the uSD may not have any vibration issues.
I think it could be fun as well, especially for the Propeller. You could even go as far as plugging in a composite video display to your rocket and have the Propeller generate various graphs/displays from the results of your launch. How cool would that be!?!
Good, because I have an idea I think would be useful in a lot of RC type projects. It's kind of along the lines of Ken's desire to have the Propeller take the place of an ESC programming card. I'm thinking I should probably start a different thread about the idea and add a link to it from this thread.
I agree. I attended a science teacher convention about 20 years ago and rocketry was a popular topic at the convention. I think of the tools we have now and how much more interesting a rocket launch could be if there were a lot of data that could be collected and analyzed.
I've often wished I has a datalogger like this.
I'm not sure if vibrations would cause a problem for a uSD card, I've just seen a lot of videos of things in rockets getting ripped apart/open from the extreme acceleration the rockets experience. I think adding additional memory of some soft as a backup to the uSD card might be needed but I'm not sure. I wonder if some uSD sockets would be better suited for this task than others?
I suppose a bit of experimentation is in order.
IMO, very!
It's been years since I've set off a rocket. I know I have several and I also have some (pretty old) rocket motors. This has sure got me thinking of dusting off some of my rockets.
I noticed the datalogger in the other thread looks very large and must have been used in a very large rocket. I'm thinking a datalogger would get more use if it could fit in "normal" sized rockets. I'll measure one I have in mind. I have a two stage rocket with a clear payload section. The payload section is 24mm ID. I think a datalogger that was able to fit in a 24mm ID tube could be used by a lot of schools and organizations.
Did you have a size in mind?
Yes, this could be a lot of fun.
Edit: I see from an earlier post you're thinking of a 3" x 4" size. I'm inclined to think a long thin board would see more use. Maybe 24mm x 72mm? Some of the sensors may need to be external to the board with very secure wiring.
Yes, I like this idea. We will probably need to do some thinking about how to use SPI like this. Each SPI device needs its own chip select line.
I do wonder if we want to take advantage of some of the very inexpensive sensors available from ebay and have a way to securely connect these small cards to the main board.
Using those, you're back to a motherboard type thing with a set of connectors to plug each sensor into (not bad but not as cool)
I know some SPI devices can be daisy chained but I think they all have to be the same type of device in order to daisy chain them.
I know the AS5055 magnetic encoders I've experimented with can be daisy chained but I don't think they could be daisy chained with other SPI devices.
One problem with daisy chaining items is the need for two connectors instead of one. Connectors take up a lot of space on a PCB and they cost a bit of money.
I think figuring out how to connect external sensors could be a big challenge especially since different sensors require different numbers of pins and supply voltages.
Do they make smaller gauge bullet type connectors? Those might give some flexibility for reconfiguring.
That same setup would work for rocketry and be very durable. There are other methods as well that could use the same footprint on the PCB. From a PCB size standpoint, I guess I would say whatever is the widest you can have that would still provide the largest customer base (AKA variety of rocket diameters that could use it) It would be rather easy to put a large amount of versatility into a 24mmx100mm PCBA.
For interconnects, go with a standard set of connectors on each end but also add some accessibility to additional IO as mentioned. Since the board would more than likely be doublesided SMT, you can have connectors on both sides for each end. A 5 or 6 pin connector on top and bottom at each end? Keep parts on one side of the board to a very low height and that side could be used to stack add-on boards using the expansion IO holes.
In searching for an example "narrow" PCB picture, I came across this one that runs $321 at Apogee Rockets but does require a HAM license for use in the US:
TeleMetrum (open source)
This is a recording dual-deploy altimeter for high power model rocketry with integrated GPS and telemetry link.