Rocketry recovery deployment timer - Electronic Circuits Projects Diagrams Free

Shax · 9th January 2007, 02:11 PM

I've attached a foto (if it uploads!!) of a 2 channel G-Switch activated timer for deploying the recovery system of my high power rockets..

Fully programmable dual channel output
30Amp mosfet outputs to fire the charges..
Launch detect
16X2 LCD to show status of the timer.
Clumsy user detection prevents premature ejection charge firing.
Usable to about 4 minutes straight up at Mach 2... Dunno how high that is!!!

Uses a 16F676 pic.
coded using Proton Plus + Compiler

I'll put a zip of the PCB and HEX file up if anyone is interested..

ljcox · 10th January 2007, 04:06 AM

Thanks for the photo.

What is the G switch? I presume it is an acceleration sensor. Are they easily obtainable?

Shax · 10th January 2007, 09:27 AM

Len,

the G-Switches are simply acceleration triggered switches, and are very easily available. They come in a range of different activation levels too..
The ones I use are produced by Assemtech, and every major component reseller seems to stock them. UK price is about £2.50 each..

I've attached another foto, if you look under the LCD, you can just make out the gold coloured G-Switch.

William At MyBlueRoom · 10th January 2007, 06:18 PM

Pretty neat, looks like the Robin PCB I just had made. Do you have a schematic you can post?

Does it launch with the rocket or stay on the ground? If it stays on the ground what is the acceleration switch for?

**Nigel Goodwin** · 10th January 2007, 06:40 PM

Quote:

Originally Posted by William At MyBlueRoom

Does it launch with the rocket or stay on the ground? If it stays on the ground what is the acceleration switch for?

I think you already answered your own question?.

Shax · 10th January 2007, 07:07 PM

It goes up with the rocket... And hopefully, back down under a parachute... Ballistic recovery has a tendency to bollox the electronics and airframe!!!!!

I don't have a schematic as such, it was all done as a direct pcb layout from scraps of paper, direct into Sprint..

The pcb layout does have the comp overlay. It's such a simple circuit, that it should be easy to follow what's going on from the overlay...
Took longer to get the code working right.... All done in Proton picbasic, over a couple of evenings..

I'll post a link to the zip soon...

philba · 10th January 2007, 09:26 PM

I had a sort of related question - why does it have an LCD on it? I think I'd figure out a way to remove it for flight.

William At MyBlueRoom · 10th January 2007, 09:26 PM

I thought it did, but isn't weight and size a problem? Why are you sending the LCD display up?

Shax · 10th January 2007, 11:12 PM

People tend to think that a light rocket will perform better than a heavier (note, not heavy) one.... Try throwing a feather and then try throwing a pea.... A pea will go further.. Most rockets NEED some extra weight in the nose, to keep the CG in front of the center of pressure.. The display goes up with the rest of the avionics because it is easier that way.. And I have immediate visual confirmation of the flight events.. My timer is used as a backup for the primary flight logging avionics.. Big rockets are expensive to lose... And that's why I also use an RF beacon to locate it on the ground... All designed, coded and built by me!!!

The LCD is a standard 16x2 parallel LED backlit display, used in 4 bit mode. I think I paid about £2.00 on ebay... (Futurlec do some great deals on LCD's too...)
But at the end of the day, there was nothing available on the market that did the job, so I built my own... And got a great deal of satisfaction doing it. OOOPS.. rambling on.. SORRY!

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10th January 2007, 04:06 AM	(permalink)
ljcox	Thanks for the photo. What is the G switch? I presume it is an acceleration sensor. Are they easily obtainable? __________________ Len

10th January 2007, 06:18 PM	(permalink)
William At MyBlueRoom	Pretty neat, looks like the Robin PCB I just had made. Do you have a schematic you can post? Does it launch with the rocket or stay on the ground? If it stays on the ground what is the acceleration switch for? __________________ Bill Home of the Firefly PIC Tutor Inchworm ICD2 http://www.blueroomelectronics.com

10th January 2007, 07:07 PM	(permalink)
Shax	It goes up with the rocket... And hopefully, back down under a parachute... Ballistic recovery has a tendency to bollox the electronics and airframe!!!!! I don't have a schematic as such, it was all done as a direct pcb layout from scraps of paper, direct into Sprint.. The pcb layout does have the comp overlay. It's such a simple circuit, that it should be easy to follow what's going on from the overlay... Took longer to get the code working right.... All done in Proton picbasic, over a couple of evenings.. I'll post a link to the zip soon... __________________ ==== Shax. ==== A bus station is where a bus stops... A train station is where a train stops... On my desk I have a work station... Nuff Sed!!!

10th January 2007, 09:26 PM	(permalink)
philba	I had a sort of related question - why does it have an LCD on it? I think I'd figure out a way to remove it for flight.

10th January 2007, 11:12 PM	(permalink)
Shax	People tend to think that a light rocket will perform better than a heavier (note, not heavy) one.... Try throwing a feather and then try throwing a pea.... A pea will go further.. Most rockets NEED some extra weight in the nose, to keep the CG in front of the center of pressure.. The display goes up with the rest of the avionics because it is easier that way.. And I have immediate visual confirmation of the flight events.. My timer is used as a backup for the primary flight logging avionics.. Big rockets are expensive to lose... And that's why I also use an RF beacon to locate it on the ground... All designed, coded and built by me!!! The LCD is a standard 16x2 parallel LED backlit display, used in 4 bit mode. I think I paid about £2.00 on ebay... (Futurlec do some great deals on LCD's too...) But at the end of the day, there was nothing available on the market that did the job, so I built my own... And got a great deal of satisfaction doing it. OOOPS.. rambling on.. SORRY! __________________ ==== Shax. ==== A bus station is where a bus stops... A train station is where a train stops... On my desk I have a work station... Nuff Sed!!!