Sensor data acquisition

Hi,

I have a load cell that is hooked up on a HBM Spider box which, in turn, is connected to my PC on the serial port.

I would like to get the information that is sent to the PC into Grasshopper to graph the data. Does anybody know how I would get Grasshopper to listen on the serial COM1 port?

thanks,

wim

Replies to This Discussion

Permalink Reply by Wim R.M. Dekeyser on April 19, 2011 at 12:04am

Hi Andy,

Easter vacation on this side...

Don't worry, I'm definately not blaming you for not knowing the spider! It is kinda frustrating, though :-)

Just a double check: in the basic setup as in this picture:

... and on a PC without anything attached to the serial port. When you open the port, start the read component and its timer, do you then get a stream of <empty> values in the log output? (hmmm... I suppose that's only reasonable - but still, you are also seeing this?)

I suppose that, because of the mutually exclusive behavior of both the spider and grasshopper (i.e. only one at a time can access the COM port), we can deduce that we are listening on the correct port.

Am I listening on the correct pin (if such a notion makes sense at all)? If I look back to the spider software, I see that 9 channels are listed and that it's only the measured value on channel 0 that changes when I press the load cell. Channels 1, 2, and 3 report OVERFLOW; 4, 5, 6, and 7 are pretty much constant at 0.000 to 0.005 V; and channel 8 says FFFF. I do not know how things like that work so I do not know if they reflect reading from the 9 pins on the D-sub 9 connector.

As for your BTW question: no, I don't need to record all of the sensor values. I suppose that the Out value on the Read component will always reflect the most current value and that's all that I need to get on with life. In the end, the idea is that we have 4 load cells in the 4 corners of a plate onto which a vertical pipe is fixed. Loads are then put on the top end of the pipe and we'll have to visualize both direction and magnitude of the bending moment that is calculated from the compression - tension readings from the load cells... We've done this on a scaled model and streamed load cell information into MatLab. Now we'll have to use a different datalogger and I was hoping to be able to do the post processing in Rhino.

wim

Permalink Reply by eric brown on May 2, 2011 at 5:35pm

I'm having the same problem!

I have a sensor that constantly broadcasts a stream of ascii data that I can read with Hyperterm (with some difficulty) and 'Advanced Serial Port Terminal'. But with Firefly all I get is this:

Please note, I am able to write data to the sensor (Activation commands and config data) when I set the 'start' values accordingly.

Permalink Reply by Andy Payne on May 2, 2011 at 6:21pm

Hi Wim,

I'll try to look more into this problem over the next day or two. I should say I've added some more code so that hopefully it will no longer try to record empty or null data. Unfortunately, this wont be available until the next release... but hopefully this will be soon.

Cheers,

Andy