Hi 
i'm totally new to arduino. I want to make a circuit that will activate the second stage of a rocket. So the circut that i have in mind is : a flame sensor which will be connected to an arduino UNO, and when the flame sensor detect the flames of the first stage he send a "message" to the arduino. Once the message is received there is a delay of 5s and then the board activate a led that will be detected by a light sensor which will power on an aux circuit and light up the fuse of the second stage. The part with the led and the light sensor, it is to replace the conventional relay, which i don't have right now.
So my actual question is, how do i code this in the editor ??? Because i don't have like 0% ideas!
Thanks for your help in advance !
do you want to learn or do you want someone to code this for you?
if you want to learn, you should start with simple tutorials going through the language (C++) and the Arduino functions and build from there. You can find plenty flame sensor tutorials on line, here is one
https://create.arduino.cc/projecthub/SURYATEJA/arduino-modules-flame-sensor-6322fb
if you want to get someone to do this, then the Jobs and Paid Consultancy - Arduino Forum is probably the best place. Make sure you mention your budget.
Flame sensor seems a bit overly complex, run a thin wire across the nozzle of the first stage engine and detect when it burns through.
You can get smaller and lighter Arduino boards.
You might be able to do this directly with a transistor, MOSFET or small relay.
Tell us about your rocket, and the "aux circuit" design.
a7
A "Rube Goldberg machine" approach, then. Sounds like fun!
that's what I thought too!
might be better and more useful to consider using mcu 6050 accelerometer instead of a flame detector
I assume the flame are from ignition of the rocket.
if OP were to turn on the arduino with the same switch that turns on the rocket, then you just need a delay() in the setup and then use some sort of transistor to activate the second stage.
Attiny13 would be more than sufficient, no way do you want the weight of an UNO just for a timer.
yeah but that’s the problem: i can’t buy right now a mofset so i searched on the web and i saw that we can do a kind of mofset with a led and a light detector.
In big lines the circuit looks like this
The flame detector is on the top of the stage not in the nozzle. It will detect the fire just when the first stage will burn entirely
i know i thought the same but it’s the most easier way actually with the components i have
I want to learn but i don’t know from where to start this is why i described the project to you so that maybe you can orientate me.
But thanks for your advice i will start then by learning C++ .
I see, THX and nice drawing.
Theoretically your igniter idea looks good on paper as a concept.
But I do not think the current and resistance of the igniter will match the current and resistance of the light sensor.
I don't think a simple series circuit (voltage divider) as you have drawn it will function properly.
If you already have the parts, try some simple experiments, you may get lucky.
If you don't have the parts, look at the specifications of the three components in the firing circuit and see if it is practical.
I also recommend including a switch so that during transport and setup the igniter can be switched out, so there is less possibility of a misfire.
a7
yeah it might be a good idea 
i didn’t thought about that
but i have the parts actually, and i tried the circuit and it’s working fine ,even i a series circuit
the only problem i have is that i do not know how to code this on a arduino 
thanks for your advice
and good evening
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