So please tell us: what is the deal with pin A5?


#1

Since I bought the KA03 kit recently, I made a habit out of following this thread…

The posts here vary from not getting this shield to work in the first place - due to unclear operation instructions, or obscure code - to the deeper inner workings of this shield and what it can and certainly cannot do…

I have worked out most of this by now:

  • I have rewritten the code in such a fashion, that at least the workings of this shield are becoming clear,and how to operate this shield: this shield is capable of driving 2 separate DC motors at various speeds, in both clockwise and reverse direction; independently… this rewritten code can be found in a thread, I posted earlier…

  • this shield should also be capable of driving a bipolar stepper motor; I yet have to figure out, what that type of motor exactly does and how it operates; but I do now, that this sketch is capable of feeding two separate motor coils independently… how to make this work for a bipolar stepper? please inform us…

  • it is clear to me now, that this shield should be able to drive regular steppers; if we include the internal library Stepper.H, I presume… too bad, the example code does not include any hints on this subject…

What I haven’t figured out yet - and many with me - what is exactly the deal with analog input pin A5?

As far as I can make out this pin is connected to the board power, via some kind of voltage divider/ripple circuit; my presumption is, that this might be useful in cases were we connect an external voltage supply, and switch from INT to EXT on the power jumper; in that case A5 holds a reference to the main power source via analogRead(5), like Vin does for internal power; but why not use the Vin pin for this? isn’t that, what this pin is supposed to do?

I cannot tell, if this is a useful board feature; but I do know, that people should be made aware of this: you cannot use A5 for other purposes, combined with this shield… considering, A5 is connected to the board power, it is not hard to fathom what it can do to some circuitry; this can blow up stuff, especially when we connect an external power source of up to 46VDC, to run heavier motors… pin A5 is hot…

So please tell us: is there a special reason for this? connecting A5 to the board power? is this even safe, for our Arduino?and what can happen, if we really connect 46VDC?

Regards…


#2

Considering this all, I am lucky to have advanced programming skills and the fact that I am comfortable with most electronics; I can read and understand diagrams and apart from the inner working of IC’s and other integrated black boxes, I have a firm grasp on what most circuits are supposed to do…

But even I sometimes have a big problem with these KA series Arduino shield; most of them lack proper operating and/or set up instructions and in some cases, the supporting example code is written faulty with no inline instructions to go with this… sometimes this code is utterly incomplete, like with this shield…

Of course I realize, Velleman is no software company nor affiliated with Arduino, and they have to rely heavily on nerds like ourselves to make this work; that is why communities like this forum are very important…

Still, I think Velleman should take more responsibilty; they should provide us with clear operating instructions, clear documented and working example code, covering each detail of the specs on each shield; so we get at least something that will work,when we plug it in… for the more advanced users, it would be nice to get some insight in design solutions and options…

for KA03, I have still some unresolved questions:

  • in the Assembly Manual, page 8 Connection Diagram, we see 5) Pin Select; these are the jumpers that tell motor A/B where to get their Arduino input, which should correspond with the pins we select in our code; very important to know, but there are no instructions on how to operate this…

  • DC motors have a polarity; I assumed that on 2) Motor’s, A1 = +, A2 = - and B3 = +, B4 = -… that way, at least the motors run in the same direction, consistent with the code we are sending; it wouldn’t have hurt, to mention that anywhere on this page: a couple of +/- signs would have helped some people a lot…

  • this shield also supports a bipolar stepper motor; why do we not get any instructions on that, apart from how to connect it? where is the supporting code?

  • this shield is said to support also solenoids and relays and such? how? how does the external power supply work exactly?

and ow yeah… what’s with A5? why is that pin conncted to the main power source?

Regards to all…


#3

Hi,

Just a quick answer for the A5 pin
When 46VDC applied to the power pin it goes first to a 1/10 voltage divider(R9/R10).
Which means when 46VDC is applied to the power pin, 4,6V is on the A5 pin.
This is a feature to monitor the voltage applied to the motor. So you can compensate in the case of a voltage drop.

Best Regards,
VEL337


#4

hi…

tx for the reply, and it is exactly what I thought this would be… a reference voltage to an external - or internal - power source; very handy…

but why not tell us so? we are not all wizards…

do not get me wrong: I think this stuff you people make is great… but even I cannot handle it from time to time…

best regards…


#5

updates on this subject, in the other thread… the working code bit…

best regards to all…