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I am working on a design for an model rocket launcher. I have an Arduino Nano Every in the design, and am hoping to use that of the continuity test. When the user presses the cont. check button, it will flip a relay, connecting the igniter directly to the batteries. The problem is that I have no way to tell if the circuit is complete, or if the igniter has a fault. I need some way to tell if current is flowing and the circuit is complete.

I don't think I can connect the igniter to the Arduino's IO pins, as they are only limited to 40 mA. I know a relay could work but I think there must be something better. I also know I could run the wire through a inductor, but that wouldn't really work for a PCB. (The end goal of the project)

Does anyone know of a component or process that can do this?

Thanks!

EDIT: Could something like this be useful? What is "Arduino Optocoupler Disease"?

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  • \$\begingroup\$ Put an LED lamp in series with a resistor to limit current to no more than 20 mA (e.g., for a blue or white LED, ~3 V drop, with a 5 VDC supply, a 100 Ω resistor). That's enough current for the LED to be visible even in daylight, but likely not enough to set off the igniter. \$\endgroup\$
    – DrMoishe Pippik
    Commented May 30 at 23:24
  • \$\begingroup\$ You should revise the title - you might have stated what you want backwards. Anyway, what voltage does your setup run on? \$\endgroup\$
    – MOSFET
    Commented May 31 at 3:16
  • \$\begingroup\$ How would you do this "continuity test" manually? What battery is connected (voltage), and what measurement is done? My question: if the battery you mentioned is connected to the ignitor, does that cause the ignitor to ignite? If not, then what causes ignition? \$\endgroup\$
    – Fabio Barone
    Commented May 31 at 9:06

1 Answer 1

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schematic

simulate this circuit – Schematic created using CircuitLab

here out1 enablec the continuity measurement when high accepting upto about 120uA and 1n1 will show logic high if more than 100uA flows

Q2 is to fire the ignitor r2 prevents more than about 500mA from flowing in-case there is a short circuit.

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    \$\begingroup\$ IN_1 will always be high if OUT_1 is high, even if the ignitor is broken or absent, because the base-emitter junction of Q1 will pull it high. \$\endgroup\$
    – Simon Fitch
    Commented May 31 at 5:28
  • \$\begingroup\$ That's a good point! I have now added R4 to prevent that. \$\endgroup\$
    – Jasen Слава Україні
    Commented May 31 at 13:19

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