The question is whether a triac or SSR would have an impact on the signal. detect a high voltage condition and turn the thing off. Alternatively (and perhaps smarter) tie the gate to a digital pin so that the analog input into the atmega can be interrupted at will - i.e. Tie the gate to the 2.5VDC power supply via a 10k and the thing should only conduct whenever there is AREF power. One solution I thought of (but cannot implement yet thanks to the iCircuit program being on strike again) is using a small triac or SSR in series with the coupling capacitor separating the transformer output from the Arduino. Anyhow, you brought up some very good points about startup conditions and whether the BAV99's can actually do anything to protect the Atmega input pins. It's the weirdest thing, my iPhone is showing me a longer reply from you earlier, but the web site does not. There will also be a small phase shift due to the magnetising current of the transformer and the resistance of its primary. This is not a problem if you are limiting the input current to a sufficiently low value. The voltage at the Arduino input pin will still go negative at startup with that design, until the capacitor has charged sufficiently. You could also remove the lower resistor (currently 1K) in the voltage divider if you increase value of the upper one (currently 2K2) by 50%. The 22 ohm resistor does nothing useful and might as well be removed. I would increased the values of all the resistors by a factor of 10 or 20, to reduce the effect of the capacitor on the phase shift, and also to reduce the current through the protection diodes when transients occur on the input. A lower value capacitor will cause more phase shift. So you need to minimise the phase shift in the voltage you are sampling. If you are trying to measure power by monitoring voltage and current, then you need to take account of the phase between the voltage and current. I also got similar results when I omitted the transformer and used a AC signal source directly on the resistors that would have been attached to the secondary side of the transformer.ĭo you think I should stick to the 100uF ceramic capacitor or breadboard the circuit above on a existing Mini that has already lost one ADC channel due to earlier mishaps with voltage dividers?Īlthough reducing the 100uF capacitor to 10uF only reduces the voltage slightly, it causes extra phase shift. The DC was still kept out - note the 100VDC offset I put into the power supply. using a 100uF coupling cap in terms of transferred signal. That aside, I thought it was very interesting that there was only a very small marginal difference between using a 10uF coupling cap vs. So the current flowing through the primary is somewhat fantastical. This one includes the transformer though I have to admit that I did not include the internal resistances of the transformer because they were not listed by the manufacturer on the datasheet. Kinda defeats the purpose of the save function, no?Īnyhow, I thought I'd include another screenshot. Worse, the current version on my CPU will allow me to save designs but not to re-open them later. OK if the signal amplitude is similar, not so great if you're trying to monitor two very different signals at the same time (i.e. For example, only one scope window can be opened. Don't get me wrong, it has a nice GUI, a number of elements that can be added easily (everything from simple circuit components up to ADCs) but there are several improvement opportunities. I downloaded iCircuit from the App store and I am somewhat underwhelmed by it. You can follow any responses to this entry through the RSS 2.0 feed.īoth comments and pings are currently closed.I tried out a couple of tools yesterday, including MacSpice. On Wednesday, February 18th, 2015 at 7:10 am and is filed under Everything Else, Open Source Software. It really is amazing what these tools can do, and they continue to bring a smile to my face. Warning: Source 'vin' has no DC value specified, 0V assumed. I can start with this very simple LPF circuit: Four double-pole, low-pass, LC-filtersĪnd then in the MacSpice console: MacSpice 1 -> source lpf.cktĬircuit: Four double-pole, low-pass, LC-filters In fact, I'm sure my retina MacBook Pro is probably more powerful than all the computers the EE Dept. In the subsequent years, MacSpice is around, and it's got all the models, and all the capabilities that the old SPICE had - plus some amazing plotting. And of course, that was a good 30 years ago. yes, let's just say they were some very Good Times. These are tools that I just can't ever forget, and all the time I spent on the terminals in the Terminal Rooms in the EE building. Every now and then I remember all the work I did in college, and at Auburn University with SPICE and MAGIC.
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