Low Cost Servo Deploy System

This may be of interest to some of you who are looking for an inexpensive deploy timer that can drive single or dual servo motors for parachute deploy.

We call it "ServoChron", and it's based on the MSP430 LaunchPad Eval Kit from TI, so total cost is under $10.

Complete instructions can be found on our website, and we're happy to answer any questions you may have.

https://www.uswaterrockets.com/construction_&_tutorials/ServoChron_2/tutorial.htm

HMMM, Interesting---this makes me rethink a couple projects !!

The Eggtimer will also do servo deployment, it's a baro altimeter/flight recorder so if your deployment needs go beyond a timer actuated by a breakwire then you may want to look at it... www.eggtimerrocketry.com

You could do that with the airstart channel...

pick1e said:

Cool! Maybe it needs to release some fall-off boosters too

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If you have cost constraints, use expendable boosters, or otherwise are risk averse, you can always make the "ServoChron Lite" version... essentially does the same thing, only it costs less than $4.00 (if you use an HXT900 servo).

That could be done too, it's not very hard to drive a servo from a logic level. A 555 timer and a transistor or optoisolator will do. I could also make the Eggtimer drive the "B" channel just like an airstart but with a servo pulse, but at the higher sampling rate (10-20/sec) it might be a problem, and it's such a specialized application that it probably wouldn't be worth using what little code space I have left.

I've been looking at water rockets for awhile, they look like an easy and cheap way to test electronics, at least to a point. Altitude is an issue, of course, but they don't need any special waivers or fire marshal permission like you do for rockets in CA, so flying them at a big local park may be an option. One challenge is that water rockets are a lot like the old B14 motor... you get a big kick for a very short time, then nothing. I suppose you may be able to play around with nozzle diameters a little to get a more "classic" thrust curve, but since they're so heavy you really need that kick to get them going. Maybe two fall-away boosters and a lower-thrust sustainer...

pick1e said:

I mean with the servos- I see them pulling lynch pins on booster attachments.

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Water Rockets can produce the prolonged burn that you are accustomed to with some minor tweaks. You need to reduce the nozzle diameter and you need to add a foaming agent to the water. The foam causes the volume of the pressure vessel to completely fill with reaction mass, so it does not come out in bulk at the start of the flight. With plain water, the ullage above the water contains only compressed air, which contributes a bit of thrust when the water runs out, but the majority of the acceleration comes from the water, which is what most people think of. A foam water rocket behaves more like a steam rocket, but does not get the same boost provided by a C/D nozzle. There's some debate weather the foam benefits from such a nozzle at all.

Amateur water rockets routinely fly over 500 feet, and some of the more skilled hobbyists are now able to break 1000 feet.

These rockets have the advantage of being able to easily loft very heavy payloads, so they make great experiment platforms.