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Another thing that can give you trouble is excessive noise in the power supply. You should be isolating the ground planes for your digital and power circuits. You should also run a 1uF MLCC cap as close as possible to each of the power and ground pin pairs for your MCU, especially the analog power pins if they are separate for the MCU you are using.
I am also using an I2C display so that I can free up the SPI pins on the board to use with a digital potentiometer.
It looks like the n-fet, pin A0, 5v from the MCU and the 100 ohm pot are being used as a voltage drop calculator to read the ohms of the coil (using the signal off of A8 to switch the nfet) but I don't see anything in the code to read this voltage on A0 and calculate the resistance. Did that portion of the code get removed for simplicity sake and the coil resistance is just being manually entered via code?
The biggest source of noise comes from induction and voltage spikes due to changing currents acting on impedance. Most generally, it's the parasitic impedance encountered by current flow that gives you trouble. You minimize those effects by routing return currents from power circuits away from sensitive high impedance connections.For the board you show, I can't tell for sure where the pickup is located for battery negative. It should be in the area of the orange arrow you show as common ground. You want to keep return currents for the power circuits from running through the digital plane.
I'm not understanding the get resistance with a voltage divider thing. Could someone link me or explain that? I'm guessing you'd need some actual high quality resistors?
I know an NPN transistor will work instead of the NFET, but I just used what I had. That part is working great.
The digital plane is still not fully isolated since return currents for the digital circuits are going to be common with return currents for the power circuits. Think of it as running two separate ground connections on two separate boards. One plane should connect next to the the negative pickup and the other plane should connect next to the negative pickup with no other connections between the planes. This is a two connection version of the "star topology" for ground connections typically recommended for minimizing noise in electrical circuits.
Ya craig, I expected in a failure of the Atty it would all be safe inside the box, but its one thing for a data sheet to say so, and entirely another for it actually work as designed in the real world, a point I am very sure is not lost on you! As a result of your response, I am now considering adding a simple 1 wire thermistor to measure the temp of the bottom of the 510 connector and lock out firing if it reaches a certain temp, no idea what I'll set it at yet, but thinking 170f should be the right ballpark. That kayfun was H O T, definitely over 300f, quickly tapping it with a finger felt hot similar to when you accidentally touch a soldering iron tip.Final layout of the screen for this version. A short video showing the multi button function and sleep timer.A preview of things to come, just waiting on my Femtoduino and the new screen (33x12x2mm screen with 128x32 I2C for 9 bucks from china ) to arrive and all of it will fit in the silver case 32x32x95:https://www.youtube.com/watch?v=THTb6blhewM&feature=youtu.be
That's the idea, but you should do a copper fill on the whole board, unless you're trying to conserve copper. Otherwise use a liberal width on that trace feeding the digital plane. The fill would look something like this;
Hi guys, congrats for your work!!I'm really interested in working on an Arduino controlled Raptor but my electronic skills are not as good as my development skills are.I've already written a good part of the code but I'm still trying to figure out how to get an accurate current measurement (or an accurate ohm reading but from what I understand based on your posts, it seems that calculating it based on current measurement is more accurate) and how to control the raptor output (digital pot or other solutions ??).If you have some clear explanations to give me including part numbers that would be awesome !Thank you guys for sharing all this knowledge !!!