Quantcast

Arduino Continuity Circuit and Low Power Launcher

The Rocketry Forum

Help Support The Rocketry Forum:

DaveW6DPS

Well-Known Member
Joined
May 28, 2013
Messages
474
Reaction score
226
Location
Barstow, CA
I just happened to be working on project to build with my 4H group, when I saw this "Ultimate Arduino Challenge". Since I have the basics roughed out, I thought it was worth an entry.

A few parts to procure, and we can build it. I am having the kids do the Arduino sketch, and will add it when they are done...

https://arduinochallenge.com/project/140
 

kc9qzf

TRA/NAR Member
Joined
Sep 12, 2015
Messages
59
Reaction score
15
Dave,
Something you might consider: Add a series resistor (1K or so) series to the pad, also consider putting a diode biased to the pad.
The series resistor will prevent any inductance from the leads from creating a negative voltage which could cause the processor to lock-up.
The diode (1N5817 or so) will protect the circuit if there is something north of VCC.
 

kc9qzf

TRA/NAR Member
Joined
Sep 12, 2015
Messages
59
Reaction score
15
I was looking at the little schematic below the block diagram.
 

kc9qzf

TRA/NAR Member
Joined
Sep 12, 2015
Messages
59
Reaction score
15
I had problems with long leads latching up a processor in the continuity circuit some years back. By adding the series resistance to the output lead protected the digital input pin. It was hard to figure out, but it seemed to happen more when the leads were shorted. At the time the leads were about 25ft long. I also used another output to turn the continuity source on or off. I used a 2.2K to the source with no ground resistor. The digital input was changed some years later to an analog input and can detect short to ground, short to battery or open easier than looking for the digital switch point to determine good continuity.
 

DaveW6DPS

Well-Known Member
Joined
May 28, 2013
Messages
474
Reaction score
226
Location
Barstow, CA
launch controller continuity circuit more details.jpg
This is the actual continuity circuit.View attachment 379026
I had problems with long leads latching up a processor in the continuity circuit some years back. By adding the series resistance to the output lead protected the digital input pin. It was hard to figure out, but it seemed to happen more when the leads were shorted. At the time the leads were about 25ft long. I also used another output to turn the continuity source on or off. I used a 2.2K to the source with no ground resistor. The digital input was changed some years later to an analog input and can detect short to ground, short to battery or open easier than looking for the digital switch point to determine good continuity.
The problem I have run into with trying to detect a short to ground is the low resistance of the ignitor compared to anything that I would use to prevent accidental firing.

I have had a lot of issues with noise and RF causing problems on high impedance inputs, so I do bypass the input circuit with a capacitor to reduce this effect.

I did make a mistake in the original drawing, in that I am using analog inputs, not digital.
 

Latest posts

Top