Right now I'm manually dispensing (using a volumetric measure) into the scale pan, then working up the weight to the desired value using a two-speed electric trickler. Essentially the powder dispensing and measuring portion shown in this video.
From what I gather reading the various documentation from the vendor, the scale can send out status & data and receive some basic commands via this serial port. The trickler, being electric with two push buttons for slow or fast speed shouldn't be too hard to control via a couple relays or something similar. Ultimately I'd like to have a setup where I can input a target value, push or click a button, and have it auto-magically dispense and trickle the charge to the desired weight (plus or minus a reasonable tolerance).
I've been tinkering with Python and PyQt a bit recently, and I get the impression that using the pyserial module I should be able to get the readout from the scale directly if desired. I will probably test first with HyperTerminal or something to make sure I'm 'seeing' the data first, then work on getting an interface going between Python and an application dialog. I think I have a serial-to-usb adapter around here somewhere; if not I can get one easily enough.
If I get the data directly from the scale to the computer, then I'd have to 'only' use the Arduino to control the trickler... and work out the code (in Python) to take the value from the scale and send to the Arduino via another serial connection how much to pulse the trickler to hit the target without going over. I do worry a little about the computer getting bogged down by some other process running unexpectedly - not sure if thats really a valid concern or not though?
If I have the Arduino get the data straight from the scale as well as control the trickler, then the only 'need' for the computer would be to send the desired target setpoint, and to retrieve the final value for display/recording.
Or... if I had some sort of LCD display and numeric keypad set up on the Arduino, would the computer be necessary at all (other than programming or setting special parameters).
Thoughts or suggestions?