So after reading several posts about various RTCs available, vs. using mains frequency, I've collected a few thoughts.
I don't see much talking about RTCs from SII (Seiko) or Intersil, which sport (in some cases) 1ppm of resolution (presumably, you have to hold your tongue right, and perform other rites to achieve this). I do see a thread on the Intersil ISL12022. I'm not thinking of buying one of these (yet), just curious.
But if you're really interested in extremes, there's the Atomic clock on a chip, which has yet to go to production, AFAIK. Might be a bit of a wait before we see one on a breakout board from Sparkfun, or someone else.
OTOH, maybe this is all a bit much. There are, apparently, people willing to spend $300,000 on a watch that tells only day and night. Heck, I can duplicate that with a Promini and an LDR.
BTW, in case anyone doesn't get the post title: (long intro version)
Something like: Hot wire -> 1M resistor -> some other value resistor ->1M resistor -> neutral wire. I would measure the voltage across the middle resistor at the arduino and tailor the value to keep it in the 1-2 volt range.
Maybe I'm missing something, but that sounds like: (obviously, I should have put a load on the far right line)
So the voltage is always going to be nominally 110VAC. So that doesn't tell you anything about how much current your freezer is drawing when it's running. Don't you need something more like a clamp-on ammeter?
A piezo detects vibration. Taped down like that, how is it supposed to vibrate?
Do you think that packaging tape is much of a damper? If the sensor is in contact with the table, and the table is transmitting sound waves, doesn't the sensor perform better if it's kept in good contact?
Well, I wired it up sort of like your circuit here. Except I have a 220Ω R for the green, and a 330Ω for the red, to try to balance the intensity a bit. Kinda makes me go meh as a quickie visual indicator of over/under temp, which is where I was hoping to use this -- right now, I'm using a pot as a proxy for a temp. sensor. The shading is somewhat poorly mixed, so the yellow midpoint doesn't really look yellow.
Might be I'll need to go for a RGB LED, so I can ramp the color more clearly away from the OK state.
i'd like to control a proportional solenoid valve, the valve is 12vdc and is controlled by varying the current from 0mA to 330mA. I'd like to use a pot to vary the current. Connecting the pot is not a problem as there are loads of examples of reading a signal from a pot suppiled with 5v.
The part I could do with some pointers with is supplying 24v and a current of upto 330mA controlled by the signal from the arduino.
Well, one thing is to get a few things in order re. voltage/current. You start out by saying the valve is 12VDC, but then want to supply 24VDC. In reading the spec sheet, I see the valves can be ordered in either (nominally) a 12V or 24V configuration. But current is proportional to voltage, and current is the controlling item here. The voltage needed to drive the coil with current N will be determined by Ohm's law, V=IR. If we assume that the nominal voltage is somewhat close to what will be needed at maximum current, then we can calculate the coil resistance by V/I=R: * 12/.330=36 * 24/.165=145 But what I suspect is that the voltage rating of valves is there as a guide for what sort of power supply you'll need, and maybe as a ceiling value to avoid burning out the coil. I didn't examine that datasheet in detail, but I suspect there are wattage ratings on those things, which are likely close to what you'll get if you calculate the wattage from the above. The further point is that as the current decreases, so will the voltage.
If I were trying to do this, I might look at current regulators, with the control pin driven from the Arduino's analog out. But I admit I haven't thought through all the details of that.