What kind of circuit would I need to make?
Wednesday, July 8th, 2009 at
1:51 am
I need a timer circuit that once activated, does nothing for an adjustable amount of time, then allows a separate circuit to complete it’s connection or simply supply power to another circuit.
Basically I know enough about electronics to wire from a diagram, but I don’t know enough to find that diagram. This is for an electronic fuse for a model rocket that I designed. I want to press a button or switch, then be able to walk away before it launches (or worse if I mess something up welding it)
Tagged with: amount of time • fuse • model rocket • timer circuit
Filed under: Electronic Timer Circuit
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Edesigner’s suggestion appears clean and simple.
I figure you would want to source this from a spare fuse block from an automobile (or more likely…a standalone battery). Unfortunately, I did not find very many 12 VDC TDRs on Ebay.
I found some here though…
http://www.factorymation.com/s.nl;jsessionid=0a0104471f43e97456a14ef84e8d821dad1ae6be8305.e3eSbNqNc38Le34Pa38Ta38RbNr0?it=A&id=5554
Magnecraft On Delay / Interval Time Delay Relay, Octal 8 Pin, 0.1 Seconds to 10 Hours, 12A DPDT, 12 VDC Coil, with LED
http://factorymation.info/relays/TDR-SERIES.pdf
$25.00 for the relay + $2.50 for an octal base + shipping
I’ve built a few large rocket engines, white powder w/ cast cement nozzles (a few years back) which I really did not to be anywhere nearby (even in the remote desert) when they went off.
I’m not sure exactly how your application is working but your describing an ON-DELAY circuit…The easiest way to do this is buy an On delay relay ..look on /ebay for these …the coil voltage might be hard for you to manage but they are out there..most have variable controls form a few seconds to minutes…If you really want to make one here’s a link
http://www.circuitdb.com/show.php?cid=92
you can modify the time by changing the RC values but why not just put in a variable Resistor Pot and be don with it…Have a good time with it..I love rockets as well…from the E..
Why don’t you just run a long switch wire? If voltage drop were a problem, use a relay locally (at the rocket) to close your firing circuit.
Saves all the hassle and possible unreliability of timed firing. Plus safer, if you have suddenly remembered after triggering it to run, that you forgot to take a cap off the rocket nozzle, or left your cellphone under the exhaust or some such calamity, and try running back!