Any appetite for cheap timers, magnetic switches or other simple components?

soopirV

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Hi All- there are a number of terrific devices available to the rocketeer these days, each with unique attributes, and with worthy price-points. I'm not a new vendor (I'm a BAR), I'm not an EE, I'm just a dude with limited funds to spend on a hobby who has a couple of alternate designs to test out. The concepts work on breadboard, and I'm looking to scale up through a micro-startup firm like seeedstudio. This means I have to buy a minimum of 5 boards, which I'm happy to do, but I'd be even happier if I could gauge interest in the final products. I'm sure there are better ways of conducting Voice Of the Customer Research, but I'm not looking to retire, just hoping to pique the interest of a few intrepid explorers. When I prove that the designs work, I will be hoping to commercialize the overrun- this is between 5 and 10 boards, depending on how they pannelize.
Anyway- Up for your consideration are the following two prototypes- even if you wouldn't accept one if it were a door prize, I would like your opinion and feedback!
1) Programmable timer - there are a few of these out there, so what makes mine unique? It's field programmable and indicated by switch position- no rotary potentiometers to leave you guessing (no PC needed) to any interval from 1-256 seconds (4"16sec). This is a huge range, and so can provide redundant apogee charge (set it to the motor burn time +1 sec to avoid multiple charges), it can also provide intermediate drogue deploy (if your motor charge/altimeter drogue charge fails, this can be set to deploy a period of time after expected drogue- if motor eject or altimeter eject worked, this is a cheap insurance policy!). Another use, however, is it's ability to operate as an air-start timer for clusters and staged configurations. Unlike other timers I've seen, this one is strictly linked to Gs, and the threshold can be customized. Other timers use reed switches, that can be fooled with g-force, or, worse yet, start timing from power-on- we all know that's a recipe for disaster!)
2) Visual Cues- the circuit requires positive Gees for >0.5 second to acknowledge flight. This kicks off the timer. After that, the G switch could fall off, and the cycle would complete (but just handling the rocket on the table is unlikely to trigger a false positive launch (see Section 3 for more)! While on the pad it includes such niceties as "power LED" to show it's powered on, "continuity LED" to show that the ejection charge is connected, and, once it lands, it features a special latched circuit that holds the FIRED LED on, so you know it's safe to approach. This output can be coupled with a siren to help you find your rocket, if desired!
3) Audible Cues- We all know that when working on a rocket, particularly complex ones, we can get tunnel vision! When in that mode of work, having visual cues to warn the user are not effective, so my design includes a beeper that is activated with the timing circuit. It beeps once per second once the G-switch circuit is activated. IF you should be unfortunate enough to have wired up your ejection charge, without safeing the circuit, the beeper will indicate that a discharge is pending- this is also useful to test out the circuit prior to launch by counting the beeps and knowing that your charge will fire!

Also up for consideration is a magnetic activation switch- this allows you to arm/acknowledge/safe virtually any electronics system without physical contact. What does this mean? Instead of having a rotary switch to arm your altimeter, you have a decal over an area of the tube on which you apply a magnet (provided, but also available from almost any fridge in a pinch!). The status of the switch may be indicated via LED , which shines through a thinned area of the cardboard tube/poly nose. The stronger the magnet, and the brighter the LED, the less modification you have to do. The unit may ship with a neodymium magnet that will work through 1/4" of non-ferrous material. I say "may" because I have neither inventory nor a business plan to retire on this. What I can say is that it will likely be significantly less expensive than the other magnetic switches on the market. My hope is to gauge interest, and even if there is no interest, I'm happy let folks know that it's possible to improve it. What sets this apart critically is that it is all solid-state, there are no moving parts like you'd find in a reed switch, so G-force in any direction would have no impact on the switch.

Combined, these two improvements can deliver safe dual deploy to motor-eject low and mid-power rockets, or provide redundancy for motor eject/ main deployment of small high power rockets.
 

Larry W

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I would like to see a cheap apogee accelerometer based deployment device. I have been using the PICO-AA1 for some time but have lost several and at 85 each it gets old. The pico does a lot more then what I use it for so I understand the price but many don't need the extras. I do a lot of ex motors in 29 and 38mm were apogee deployment is nice on the many lower flying rockets instead of dealing with delays. Small light simple to use so it could be dropped into any rocket and activated externally would be something I think could be useful to many. If someone wanted they could then use the factory delay as a back up if they wanted. Just my thoughts.
 
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conman13

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Id be interested in the 1st timer what would you be looking at in price??
 

hball55

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I would like to see a cheap apogee accelerometer based deployment device.

+1 on cheap accelerometer for apogee deployment.

I have a PICO also and am just now setting it up in one of my rockets. I have also been using Magnetic Apogee Detectors; the Robert Galejs model MAD I have used for fourteen years and with great success and now the new ZeptoMag w/accelerometer for launch detection arming which will be used for the first time soon.
 

AndyC

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+3 on cheap accelerometer. If it looks good, $30 would get me to buy; $40 maybe.
 

patelldp

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+4 on cheap accelerometer. If you could make something that records flight data, even if it's in a simple format that is loadable into Excel, that would be awesome. Basically all I'd want is a column for time, a column for acceleration, and a column for velocity.

If you could make that accelerometer have an apogee output, that would be even better! This unit wouldn't have to be at all programmable, just make it sense apogee out of the box and fire the charge. Only two terminal blocks or solder pads would be necessary for the output channel and the battery input (break positive lead for switch). I imagine that something like this would be very small.
 

Reinhard

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2) Visual Cues- the circuit requires positive Gees for >0.5 second to acknowledge flight. This kicks off the timer. After that, the G switch could fall off, and the cycle would complete (but just handling the rocket on the table is unlikely to trigger a false positive launch (see Section 3 for more)!
(emphasis mine)


Please note, that this approach will fail with certain motors:
A) Motors with a rather short burn time, e.g. the smaller core burning motors with AT Warp 9 and CTI Vmax propellant.
B) Strongly oscillating motors. This can be the case with hybrids and has caused problems with altimeters that didn't account for this in the past.

You can make a much more robust launch detection with an accelerometer and the proper signal processing. Thanks to smart phones, low range 3-axis sensors can be bought rather cheap (starting at ~$1). These sensors are perfectly fine for launch detection purposes, however, they might not be the right choice for apogee detection, because clipping the signal at 8 or 16g will create inaccuracies on high-g flights. For this, you would have to invest a little more for a sensor, but looking at this thread, there appears to be enough interest.

Reinhard
 

Maxitout

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Hi there! An acceleration based deployment did exist for awhile. I have 2 of these, it's called a Motor Topper. One of our club members, Dave Flynn, used to make these, but I haven't seen him at a lunch in awhile, and his website is no longer around. These do work great! It will deploy the parachute at apogee, and also blink out the time to apogee, and altitude reached, (within 100 feet). These originally sold for $65.00, (a little steep, for what it is). Also, these were sold for a short time by Giant Leap Rocketry, as part of the Slim-Shot system. IMG_0932.JPG
Phil L.
 
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