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You are not understanding what the mosfet is doing. When there is 10V on the gate, source and drain are connected. If the source is connected to ground, then the drain is connected to ground. You will not get 12V on the drain while the mosfet is ON unless you have blown the mosfet.
that drain connects to ground....completing the circuit to +12V.  I do see 12v on a multimeter, but its not blown as I can turn in off & pwm it just fine...maybe the new drawing with change your view on this?


Now, with the resistor divider, if there is ground attached to the bottom end (mosfet ON), current is moving through it, and you will see 1.2ishVDC at the center. With the mosfet OFF, that 12V potential extends all the way to the drain of the mosfet, also putting 12VDC to the Uno.
i have seen that 1.2v you are talking about, i ive even worked with that spec from the datasheet. I have more to say/ask about this, but please look at the updated drawing and see if that changes your view at all.



Perhaps update your drawing to what you have, use a SPST momentary switch for the electrodes. Show the load as a resistor.
i think i did this as you asked, if its still unclear, just ask
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post the datasheet

Relative to the gate of course.
http://www.irf.com/product-info/datasheets/data/irf3205.pdf

Ok, so when the gate is charged with 12v what is the voltage at the gate? And then when switched to ground what is the voltage relative to the gate?
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Project Guidance / Re: Compartment occupied detec...
Last post by wvmarle - Today at 03:04 am
18 feet - almost 6 meters tall - how are you going to get the objects in there in the first place?! I'm quite tall myself but even so can't manage that height without ladders or so.
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post the datasheet

Relative to the gate of course.
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At the moment my heads spinning.
That's because you've bitten off more than you can chew and breathe at the same time,

but if you're willing to put in the effort then more power to ya.
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Project Guidance / Re: Basic DS3231 RTC questions
Last post by PeterPan321 - Today at 02:59 am
It would help if you would provide a link, in case there is more than one version of that library floating around, or more than one library by that author.

Is this what you are using? http://physics.csuchico.edu/%7Eeayars/code/DS3231.zip
Same author, same date, yet the author had called the folder "DS3231-1.0.2", and indeed had appended some extra code to it, including some that was similar to your calls, getting multiple registers at once

Here is some of my old code I dug up. I believe it deals correctly with both issues you bring up.

Yes I ended up doing something similar... requesting multiple registers at once, starting with seconds, since that toggles a 1 second freeze between the live registers and the ones exposed for user read, specifically to make rollover impossible. My particular project only requires day time (seconds, minutes, hours), so thats all I read or write in one shot.

Thats a good idea you added, reporting an error if the number of registers available is less than what you requested.

But you are still using the original WIRE library, and I've been lead to consider alternatives like Wayne Truchsess' I2C library, which boasts more built in lockup avoidance, faster operation, and reduced code footprint. The trouble is, the DS3231 support code seems pretty easy to trace out and rebuild your own way, using these newer calls. But doing this with the LCD library is much more complicated, and once I go down that path it makes little sense to NOT do the same for every I2C device I ever use.

So that said, it looks like the only sensible thing is to analyze Wayne's work, and build a wrapper class around it to mimic the WIRE library as closely as possible, so that ANY I2C device with a support library can make use of the better calls without modification.

Perhaps I'll write to the author and ask why HE stopped doing that.
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Project Guidance / Re: Breadboards and liquid el...
Last post by wvmarle - Today at 02:58 am
Breadboards are for tinkering, for anything that has to last beyond your desk you have to solder it on perfboard, stripboard or protoboard. Those soldered circuits are much more robust, stable, and lasting.

Breadboards also have high levels of stray capacitance, resistance and inductance. For some projects that can be a serious problem as well.
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Project Guidance / Re: Environmental control syst...
Last post by profk007 - Today at 02:56 am
Hello again! I have purchased the 5v buck converter and used the onboard potentiometer to bring the 12v 800ma power supply down to 5.3v...

I connected everything, (after burning through an Arduino and 3 of the 5 buck converters) but the Arduino fails to boot, along with everything else connected to the new 5.4 volt power supply...
The fried Arduino powers up (onboard LEDs) when connected to the 5.3v source and ground coming from the buck converter, but nothing else.

What is going on here? Should I raise the voltage slightly?
(5.4v confirmed with a multimeter.)
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Sensors / Re: adc converter with arduin...
Last post by Wawa - Today at 02:56 am
you how you can convert an analog signal to digital with arduino  in a voltage  range different to 0 -5 V , for example, from 46 V to 54 Volt

result:
if  Vin <46 V  result 0
if  Vin >54 V result 1024
Can be done the complicated way with a voltage shifter circuit with opamps.

Or the easy way, with a higher resolution external A/D.

A 16-bit ADS1115 with a simple 2-resistor voltage divider could return more than 1024 values in that voltage range.
Leo..
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Programming Questions / Re: If statement problem
Last post by VoltMaster - Today at 02:56 am
Cheers FIXED, this is what happens when you cut and paste.
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