Advanced HMI Multi-touch?`

janner_10

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We have a job coming up where the customer wants the HMI on a tablet, connecting to a Compact Logix.

It is a Win 10 Pro tablet. I assume AdvHMI will handle this, but does it also support multi-touch?

The customer wants a deadmans switch and a jog pb on one of the screen.
 
An HMI based dead mans switch? Sorry I'm not directly answering your question but if it were me that would be hardwired...
 
It's not actually a legal requirement, it's just they want to jog the machine by pressing 2 buttons instead of 1, so deadmans switch was probably poor terminology.
 
I guess it's less of an aHMI feature than the tablet feature. I tried it there on my Surface RT and it entered two keys of the keyboard at once. Unfortunately, being RT I can't test aHMI for you. Vb is generally expecting only one button press at a time as why would there be the mouse in two points at once.

I guess it's no different to having a latching button true and a momentary button true (and if "multi touch doesn't work, this is what I would do; have a toggle button that is password protected/hidden for "jog enabled"). The code will be simply a boolean AND of the two states.

I would still ask the customer why they want this.

P.s. "multi touch" generally refers to the ability to pinch to zoom or rotate objects
 
monty-python-run-away.jpg
 
The usual rationale for a two-hand switch is to keep both of an operator's hands away from a dangerous area when initiating motion. It's hard to understand why the client would want something like that implemented on a tablet where an operator could most likely use two fingers on one hand and still be able to place his other hand at risk.
It seems to me that requiring two sequential touches rather than two simultaneous touches would be a better strategy. That would reduce the likelihood of accidentally starting motion if someone touched the wrong area of the touchscreen by mistake.
 
I haven't had the luxury of playing with AdvancedHMI, but some HMI systems have the ability to program pushbuttons to run different scripts for "ON DOWN" and "ON UP", where one can set and reset a command bit (like a jog).

Normally, I don't trust such logic, as experience has shown that HMI packets can get misplaced, and on a quick press/release the "On Up" bit reset can arrive before the "On Down" set, thus latching in the command until the next button press.

The two-hand strategy -- where two independent bits are reset if only one bit is active for more than say 0.25 sec -- is not a terrible way to compensate for the problem, if coupled with a "Jog Mode" to both enable the buttons and to exit if things go sideways. Assuming that AdvanceHMI allows a second button to be pressed while another one is also pressed. This can't be done with a mouse, so probably can't be done with fingers, either.

The above advice -- RUN AWAY ! -- is probably a better solution.
 
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