"56 Bytes of Non-volatile memory available to user" - this is RAM, not EEPROM.
You can plug the battery backup to the wall to keep it charging at all times, and then power the arduino with one of the 2 USB outputs. At least in the one ive got, this works perfectly, so if there is a power failure it will keep running from the battery for quite a long time. Then you would just need to make a way of knowing that a power failure has happened, which should be easy with a digital pin.Very interesting your project. - Thank you I appreciate it.
I'm interested in this Shield, one thing on my mind that I need is, like CR2032 3V Battery and MicroSD memory at the same time that enough to power and save the data on schedule respectively. Which one can you suggest Paul?
Quote from: dc42 on Oct 22, 2013, 04:57 pmThe two most obvious solutions to me are:1. Use a capacitor to power the Arduino for a fraction of a second when power is lost, and add a mechanism to detect loss of incoming power. If you power a Uno from 12V via the barrel jack and you don't connect anything that takes much current to the +5V pin or the output pins, then a 2200uF capacitor connected between Vin and ground will power the Uno for about a quarter of a second, which is way more than you need to save important data to EEPROM. You can detect impending loss of power using an Arduino input pin.Seems this point would work for me, I'm still not decide which power supply level do I have to use either 12V or 5V, one thing on my mind is to use the Arduino power as shown on the link below:http://www.ebay.co.uk/itm/5V-4-channel-Relay-Interface-Board-for-Microcontrollers-Arduino-PIC-AVR-MCU-DSP-/130937144756?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1e7c7645b4
The two most obvious solutions to me are:1. Use a capacitor to power the Arduino for a fraction of a second when power is lost, and add a mechanism to detect loss of incoming power. If you power a Uno from 12V via the barrel jack and you don't connect anything that takes much current to the +5V pin or the output pins, then a 2200uF capacitor connected between Vin and ground will power the Uno for about a quarter of a second, which is way more than you need to save important data to EEPROM. You can detect impending loss of power using an Arduino input pin.
Now, I have this coffee flow sensor that it has pulsating output but input to the Arduino I/O terminal, the flow sensor has a magnetic contact inside to open and close the circuit and gives 5VDC at stationary position and 0V at the other way, but when it is rotating at a different speed everyday due to the pressure that pushes the water out, the voltage output or input to Arduino may read 2.5 or 3.3VDC, is the UNO or other controller can set to threshold voltage of 1 (ON) and below 1V is 0 (OFF) depending on the voltage or current input?
If a power outage occurs, in the process of recovery you examine the data in the BBRAM, see if it that data has been put in the EEPROM, check the EEPROM data in general (in case the outage occur at the moment of it being written) and complete the above procedure as necessary. This is essentially the same process as you expect your PC disk system to do in "journalling".
Are you saying that the sensor provides 5V or 0V, but the average voltage may be 2.5V or 3.3V?
I still don't get the idea on writing environment and trying to catch it up; in layman's term, having CR3032 Shield would protect my data from power failure or it would still remain?
More than that I cannot say without a reference (URL) to the flow sensor - did I miss this earlier?
yes seems you missed that earlier, this is the URL
but 10k looks good on my testing but can I use 330 ohm instead, to increase the current sink from 0.33mA at 10k to 10mA of 330 ohm with 3.3V?
Interrupt is my last option
If there is better idea ... The quantity of the High state per peak on cycle may vary as the source code increases due to total loop cycle time.
Why would you be using a pull-up on the output from a Hall sensor? Where does it say you might need this?
No, it simply isn't an option at all.
counting each change from a previous state.
I'm not sure of the impedance on I/O terminal, but instead trying to sink in consistent current input to make sure signal is delivered, I might be wrong on this idea.
great, just to catch expert's advise.
This is where my brain is bleeding, by replacing delay with clock frequency monitoring. Can I change processor timer or frequency to align within the window of sensor?
Sounds as if you are not familiar with digital circuits!