[57north-discuss] Missing component

[Robert McWilliam]

On Tue, Nov 17, 2015, at 12:37, Tanev, Ventsislav wrote:
> I was originally hoping to measure the current consumption with a
> multimeter, but the current consumption might fluctuate too quick for
> me to register meaningful data. What I believe will work is to measure
> how much power will be consumed with a current sensor (ACS712) and log
> the data. However as I don't have such sensor and the estimated
> delivery for one is way past my deadline I was hoping that you guys
> have 1 I could borrow.


> In all cases any feedback would be greatly appreciated 😊


I think the current sensor chips are overkill for what you're doing
here (and the power changes you'll be looking at will be a few orders
of magnitude from what they're designed for so might be lost in the
noise): the devices you're looking at are powered by low voltage DC;
just put a known small resistor in the power line and measure the
voltage across it.

The (slightly more) complicated part will be logging the data. What kind
of time frame are you talking about for the building and sending the
message/object? I expect it's much shorter than you have any change of
getting with a multimeter, pencil and paper. I have a Red Pitaya[1] in
the space that I think would work for this. It could be set up to grab
voltage readings at whatever period is needed (well, probably: max
sample rate is 125MS/s) based on trigger on the other channel, then put
one channel over the resistor and the other to a button that's also
connected to the pi/arduino to trigger message building and sending. Can
have the data output to python or matlab (or some other places) for
further processing.

Robert

[1]http://redpitaya.com/

--
Robert McWilliam      rmcw at allmail.net    www.ormiret.com
 
Cleverly disguised as a responsible adult.
 
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