Re: sport rocket staging timer



Smaug Ichorfang wrote:
Found something I think will work well. Even buying the parts at retail+ (like radio Shack), the cost should be well below that of a commercial timer.

see: http://www.vernk.com/G_Switch_Timer.htm

That is unnecessarily complicated and RS has dropped their logic line. How come you can't use the g-switch alone to trigger the circuit and skip the timing from liftoff? The amateurs can't figure out how to do it? And why do you need a delay from 1st stage burnout to 2nd stage ignite, why can't you just use the g-switch dropout to trigger the 2nd stage igniter immediately?


This should do until I decide to jump into the 1990's and get the equipment to program pic's.

Picas are overkill for this simple app.


The one mod I'm thinking about is to replace the "fire" transister with an SCR. Maybe not, just somethign to play with when I breadboard the circuit.

You don't want an SCR for a few reasons such as too much terminal voltage drop in a low voltage app and they capture transients, something you want to avoid. An ideal switch would be something like the FDC637BNC N_channel MOSFET in miniature package, low voltage threshold, very small resistance, cheap and in stock at Mouser:
http://www.mouser.com/Search/Refine.aspx?Ntt=*FDC637BNZ*&N=1323038&Ntx=mode%2bmatchall&Ns=P_SField&OriginalKeyword=FDC637BNZ&Ntk=Mouser_Wildcards

.

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