many a boy found out the hard way not to use mothers GOOD breadboard, and most had to stand up eating for a week.Re not an electronic breadboard, but a chunk of wood w/brass pins, old school style
I have to mention this..... I always wondered where the term came from. Not sure what she was supposed to cut the bread on...
I figure that the 7805 will be fine, I am sure I have a few, so I didn't bother looking further.Anyway, enough rambling. Getting back to the question, if you are going for a 12V gel cell to do the picaxe, it might be a bit overkill but it would certainly work. If you are using less than 100mA for the picaxe, use a LP 5V reg, eg LP2950. If 100mA to 1A, use a 7805. No heatsink needed for running just a picaxe, and if you have a 7805 already, then use that.
the 12v will also be powering radios and other gear, and I want to keep it down to one standardized power supply, with one backup. this is for a rocket, so no need to charge a second set. 7ah gel cell should tell you that even if I did need heat sinks, size doesnt matter, i've got plenty of room. might look at nicads *if* they drop a bit in price and can handle life better than gel cells.I'd seriously look at 4 nicads or NIMHs for the servos. They can handle the peak currents, and also if you have some spares, you can be charging 4 while using the other 4.
Have a look at the pic half way down the the page of the Silicon Chip mag website,Re not an electronic breadboard, but a chunk of wood w/brass pins, old school style
I have to mention this. My parents found this old bookstore recently and came home with some "Boys Own Papers" http://en.wikipedia.org/wiki/Boy's_Own_Paper from the late 1920s. So British, and exactly the sort of thing you find in a bookstore in outback South Australia. Lots of ripping yarns but also some very practical advice on how to build a homemade radio. They recommended the best way was with brass pins, screws etc, using mother's breadboard. Her real one. Just the right size. I always wondered where the term came from. Not sure what she was supposed to cut the bread on...
SLA is going on the rocket, and weight is NOT a problem. really big rocketWesty, that is my mum's breadboard!!
Oh well, off to eat my lunch standing up
Addit - tater, is the 12V SLA powering mission control on the ground or is it going in the rocket? If the latter, then we seriously need to look at weight. Every kg you lift (and a SLA weighs a few) will take x more kg of propellant. If you are going into orbit, the ratio of propellant to payload is a truly scary number. If you want to go light, what about looking at what the model helicopter people do and look at LiPo batteries?
You should have a chat with NASA. I think they're missing something!SLA is going on the rocket, and weight is NOT a problem. really big rocket
only if you are interested in maximum performance. for our flight tests we could just use supercaps if we were really worried about weight. cost and reliability are issues hereYou should have a chat with NASA. I think they're missing something!
Both they and I'll confess to it myself, thought that weight was one of the important matters in rocket design.
what the heck would anyone want that many!? yes the 7Ah is overkill, the 20watt ham radio is also overkill, but I'd prefer to have more power available in case something happens instead of a failure due to lack of power.Switching from Pb to LiPo on a 7Ahr pack would permit the fitting of ~70 PICAXE 08Ms inc PCBs.
not yet, not too worried. if it does become an issue, then we'll worry about it. fixing stuff that aint broke is not what i do.P.S.
Do you know about the affect of high accel on Pb plates?
thats the plan. if definetly questions one sanity, and I'll spare you the rants I've been having on pro-space websites who do nothing but sit and talk but never DO anythingWell I guess if you already have the battery for the 20w ham radio then it isn't overkill as you already have the battery. Heavy for the smaller rocket on that video. But probably not for the bigger one you are building. Are you really going full scale? If so (and your rockets do seem mighty impressive), do please keep us updated - I'd love to see a video.
Maybe.What are the servos for - attitude/fin control?
still thinking that one. GPS for sure, but might need a compass too, had a lively discussion with a TI worker about such things.And how are you going to steer - with the GPS or using accellerometers or some other technique? (I'm thinking of the electronics used in autonomous helicopters, which is often a hybrid of GPS, accellerometers and even magnetics/electronic compass).
nope, Different type of parachute. parafoil chute like skydivers use. fixes teh spinning issue.Re "First, I want to try a directed landing. Going to use a steerable chute and use the servos to collapse a couple cells for steering. I'f I can guarantee I can park it withing 50' of a desingated spot, the FAA should be REAL happy."
That could work. Watching the video the parachute is a lot slower than the launch. I guess the parachute should be stable enough not to spin. Hopefully not swinging from side to side too much either. And if it is rigged right the payload should be sitting horizontal. So horizontal and not spinning would be perfect for the compass to give the heading. And GPS gives the location. Then, as you say, start steering it. That would be the theory. I guess you might need a test rig where you can drop it off a height and test the parachute? How do collapsable cells work? Would 4 cells at 3,6,9 and 12 o'clock positions be enough to steer?
need a compass to know which way you are facing. been thinking of ways to eliminate that. should be able to do by keeping track of gps changes and gently turn it once it knows where it is heading.These were the links I was thinking of. Found them on my work computer:
http://autopilot.sourceforge.net/faq.html
http://www.micropilot.com/
Ok, so if you can steer a helicopter you should be able to steer a parachute. And a rocket (with fast enough math on the accellerometers during takeoff). With the parachute, assuming you are not swinging or turning, you just go forwards with a gentle turn to the right or left until facing the right direction. Use the compass/GPS for that. Then head till over the GPS waypoint making small turns for wind etc. Then circle down.
wind causes the tilt, but after it gets fast enought, the wind drops down to a insignificant fraction of overall forces on the fins, so it eventually goes strait. not steerable nozzles, but control surfaces on the fins laterFor the rocket, I guess there is the takeoff and the rocket 'falls over' briefly before the airspeed gets high enough to guide it in a straight direction. You can see that on the video - it ends up heading in a straight line, but off to an angle (and hence lands some way from the launch site). I presume you don't have steerable nozzles, so you takeoff, let it get up some airspeed, take lots of measurements on the angular rate gyro which tells you how much it 'fell over' during the launch, and then once the speed is there, steer the vanes till it is pointing straight up again.
Blimey, if a gyro is not KISS enough, you'd better completely forget about compass and/or GPS. They are 1000 fold more complex than a gyroa gyro? not KISS enough
better send me a link to whats state of the art in gyros then. maybe something has changed since I last looked at them.Blimey, if a gyro is not KISS enough, you'd better completely forget about compass and/or GPS. They are 1000 fold more complex than a gyro
Besides, if you're thinking of controlling to a GPS you'll need a gyro anyway!
How about a solid state 3-axis accelerometer?better send me a link to whats state of the art in gyros then. maybe something has changed since I last looked at them.
yeah. depends on weather we are talking flight or descent. gps for descent, somethign with faster sampling for flight, although it could do without for ascent.tater,
You can get gyros from most RC hobby stores.
Attempting to do all those calculations on the fly would be quite a task for a micro. Trying to calculate vector differences from a GPS AND do the flight control postion calculations on the fly would be much harder.
Also, don't forget, GPS updates are not very fast. Just reading the serial data strings will be several orders of magnitude slower than using either an accelerometer or gyro.