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  1. jgauthier

    Building a power monitor

    I must say, that was a complete misinterpretation on my part. That site is great, and I definitely intend to spend some time with those tools. In the meanwhile, I implemented more precise timing in my code, and I collect data for ~167ms (~10 wave forms). This is ~6000 samples, and the machine...
  2. jgauthier

    Building a power monitor

    100 samples over a period of ~200-225ms. My mains frequency is 60hz, since I'm in the US. My thought process is that a single wave form takes 1/60th of a second (16.66ms), and I want to take samples over ~10 wave forms.
  3. jgauthier

    Building a power monitor

    I got this working pretty great last night. Solid output, and the wattage (RMS) calculations are pretty close to on par with my physical meter. I am taking 80-100 samples, and the output looks like below. I can certainly do more samples for the true RMS calculation.
  4. jgauthier

    Building a power monitor

    Alright. First, thanks! I was out of town, and had a busy week. So I haven't had a chance to do much with this until the middle of the week. I've had some great success. First, I resolved my DC offset issue. While I had my schematic correct, I actually did not have the physical circuit...
  5. jgauthier

    Building a power monitor

    Harald> Ah, I understand. Duke> I considered that. I read several places that use something like a 9v AC/AC converter to obtain power factor, rms voltage, etc. One thing that wasn't immediately clear is if this circuit needed to be replicated for every single circuit breaker. Is so, that is...
  6. jgauthier

    Building a power monitor

    I spent awhile and changed everything around, including some tests. Something is not right, and I'm not sure what. First. I moved the burden resistor from 110, to 55 Ohms. This had my ADC input range from 0-3.3v. Now with 55 Ohm, it's 0-1.65V. This will allow me to offset the CT output...
  7. jgauthier

    Building a power monitor

    Harald, That's a lot to take in. I'm going to digest this, and work on #1. I really appreciate your input, as there is a lot of stuff I have not taken into consideration. I definitely consider myself a novice in this area. My goal is to have fun and learn, so here we go...
  8. jgauthier

    Building a power monitor

    So, I believe I have a suitable software solution. Let me know if I'm crazy. I'm taking 1000 samples, which executes in 41ms. Of the 1000 samples, I implement a max() function to store the maximum value. That value should be the peak current. I then simply multiply by .707 and get the RMS...
  9. jgauthier

    Building a power monitor

    Thanks. A lot to think on which direction to take. I did confirm my reading fluctuations were definitely because of the AC signal. I grabbed 4000 samples into an output file and graphed them in Excel: This looks good, other than the readings are too high. 600 would be 40 amps, and I was only...
  10. jgauthier

    Best platform for simple(ish) accelerometer logging project

    What are your requirements? Any kind of networking, or wireless? Personally, I like the Atmega chips (what the arduinos are based on). They have a good number of inputs, easy to get going, and not hard to program. You could go all the way to something like a raspberry pi, but you get more...
  11. jgauthier

    Building a power monitor

    Greetings, I own a TED (The Energy Detective) 1000 model. It's quite a few years old, and does whole house monitoring. It communicates using PLC. I decided I wanted to build my own, and use a current transformer on each circuit. This would allow me to really see where my power is going...
  12. jgauthier

    Detect ignition from OBD2?

    Well, the project goal is to attach a device to the OBD2 connector and get data from it. However, the amount of stuff I want to attach is too much for "always" on. so, I really want a trigger that can be used to go on and off. Only from the OBD2 port-- I want a single cable that is easy to...
  13. jgauthier

    Detect ignition from OBD2?

    Hey all, I am working on a project that connects to a vehicles OBD2 connector. The project is in components, and I do not want all of the components to be active when the ignition/engine is off. (To not drain the battery) I'm trying to determine if there is a reliable way to determine...
  14. jgauthier

    Help with MOSFET as a switch

    Hey Everyone, So, I built a circuit and everything was working very well. I was using a MOSFET as a switch. However, I was not happy with my design, because I was "swtching" ground. Effectively, I had two ground busses. One on the drain, and one on the source completely isolated. I...
  15. jgauthier

    LM317L Voltage drop with load

    Wow, nice catch! I just threw that together to demonstrate what I was working on, and the caps are connected to ground on the physical circuit. :)
  16. jgauthier

    LM317L Voltage drop with load

    Thanks! I see that even with a 20mA load the dropout voltage is 1.5V, so yeah. I will try another part!
  17. jgauthier

    LM317L Voltage drop with load

    Hey Everyone, I am struggling with an LM317L (TO-92) which seems to be having a significant voltage drop. Let me set the stage: 12V coming into the circuit, that is then going through a 5V regulator. I have a steady 5V. After that, the rest of the circuit is turned on with a mosfet...
  18. jgauthier

    Sizing a mosfet

    I started with an npn transistor, (2n7000) but it could not drive the load. Through some other research, I also found this one which I think will work. http://www.st.com/web/catalog/sense_power/FM100/CL824/SC1164/PF188057 At the moment, as a work around, I am using a 7n2000 triggered...
  19. jgauthier

    Sizing a mosfet

    The switching voltage will be 5 volts, and additionally the driving voltage will also be no more than 5 volts.
  20. jgauthier

    Sizing a mosfet

    Greetings, A project I have embarked on consists of a micro controller that is "always on". Based on a change, a pin will go low, and that will tell it to turn another pin high. That high pin will then turn on the rest of the circuit. The circuit load could be as high as 2A. I am...
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