You would not need to do it for the logic speed, but consider whether those grounds are carrying power between the boards.

If they are, you may still need a few grounds (rather than just one) to ensure they provide a low resistance path between the boards. The fewer grounds the higher the resistance, the hotter they could get, and there would be a voltage differential between the boards which could confuse the logic gates.

 

Paul

Thanks for the reply. The grounds aren't carrying power, they're strictly logic reference. I've got many other power grounds.

I'm designing a pass-through circuit for a project at work, and I'm running in to space issues. I have a block of thirteen digital signals and I'm wondering if I need a ground wire between each. The ribbon from my circuit to the next board is maybe 6 inches, and the signals are 0-5V logic that change states maybe once per minute. Seriously slow.

Do I really need to ground every other conductor in this case?

On October 31, VS2013 will be released. It's currently out as an RC, and I'm downloading/installing it now.

Is there any news on VS2013 support for the Netduino?

It sounds like a Raspberry Pi would be more suitable.

I'd do two identical water temperature sensors, one in the tank and one somehow in the bowl. If the readings differ significantly for a while after someone has left the bathroom, they probably didn't flush.

Programming this to work with the Netduino will probably take you less time than waiting for someone else's code. I've used SHT21s before and they're incredibly simple. However, don't query them more than once per second as they're prone to self-heating.

Ok, so basically you'll be using a software hp filter then, I suppose there are ready made functions for that in LabView but designing one in h/w is quite simple, basically you put a capacitor in series with a resistor to ground.

Might give this a try. Thanks!

Edit: gave it a try. It worked, but not as well as our current filtering idea which is the LabView-provided minimum for the differential amp.

A stupid question perhaps, but if the background is also available on its own (without the square wave) a differential amplifier would do the job. I suspect not but provided the 8 - 10V signal varies significantly less (slower) than the square wave, you can use a high pass filter to isolate the square wave which could then be amplified. That is, you would design a filter to remove everything below the maximum frequency of the squarewave (e.g. place the knee at ~30Hz).

Currently, the idea is to extract the background with LabView and feed it via analog output to a differential amplifier. It's not strictly available on its own, since the entire signal comes from a single sensor.

I don't quite follow, I thought you were trying to detect local minimums but are you in fact trying to filter out the 8V DC component leaving just the square wave?

And amplify the difference. The big picture is to dynamically remove the background, as it's not a constant 8V, but varies from 0-10V.

I meant for you to subtract the signal from a positive voltage.

It's a 30Hz square wave sitting on top of about 8 volts driven by photocurrent from thermal IR. I need to be able to dynamically adjust against that background.

Couldn't you just invert the signal (turning valleys into peaks) and then apply a peak detector on that?

I could be wrong, but I think Inversion is not a valid technique here since all signals are nonzero and positive. This isn't an AC signal.

[color=rgb(102,102,102);font-family:'Lucida Grande', Lucida, Verdana, sans-serif;font-size:13px;background-color:rgb(245,245,245);]Does anyone know a good op-amp implementation of a "Valley Detector", which I assume would be what one calls the opposite of a peak detector? I need to find the baseline of a signal so I can reject it. I want to do an op-amp circuit instead of with a DAQ so I can do it in real time.[/color]

[color=rgb(102,102,102);font-family:'Lucida Grande', Lucida, Verdana, sans-serif;font-size:13px;background-color:rgb(245,245,245);]I'm dealing with DC signals, if that makes a difference. The "valley" is a positive nonzero voltage.[/color]

I, too, would be interested in this.

It's the same as the barrel jack. You can use either for unregulated 7.5-9v input power. Both go to the regulators that power the board.

Hi all,

I had a fun idea that would add a little flair to a project I'm working on. I do instrument development for a climate research group and I'm building a networked array of instruments (using Netduino!) that communicate with various wireless protocols (WiFi, cellular networks, etc). That's easy enough, but what I want to do is write an android app to allow our field engineers to be able to use NFC communication to receive real-time data from the instruments to their phones and tablets. Previously I was just using QR codes to let the engineers connect to the webserver and automatically navigate to the relevant instrument's page, but in the case of a network failure I want the instruments to still be serviceable.

I like the idea of NFC, but I can't output data over an NFC tag without an NFC programmer of some sort. I found this:

http://www.nxp.com/d...N532_C1_SDS.pdf

I'm wondering if anyone has enough information on NFC to tell me if I can use Netduino to interface with this to produce a constant stream of NFC data that I can recover with a smartphone.

Or would Bluetooth be better?

Long wires are basically antennae for mains frequency noise. Also, they're great inductive reactance devices and breadboarding makes every connection good candidates for memristors, which screw up the inductive properties of your circuit. That's just the inherent problem with breadboarding. Whenever possible, use short wires and small circuits.

as I'm writing it's over 8x the funding target.

Maybe they can throw some funding towards developing a mini powered by the STM32F!

From the schematics, it looks like pin 9 is also shared by the SPI bus that the Ethernet encoder sits on. Maybe that's why it's not so happy being declared as an interrupt?

I've got a Rosewill PS and the datasheet specifies that the 3.3V bus has a minimum output current of 1A. I've never seen a minimum current output specified before. Does this mean that the PS will push a minimum of 1A, regardless of the current needed by the load?

Only reason I want this is b/c what if the PC got a hard freeze, and need a hard reset.

WOL can only wake up a PC when it is OFF. In the case that the PC freezes, it would still be considered ON.

Let me know if there are other easier way around this.

Couldn't you hard reset your PC by holding the power button until it turns off, waiting 10 seconds, then turning it on again? Or do you need to automate this?