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|   Jul 21, 2010 at  9:52pm

That's pretty sweet!

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|   Jul 22, 2010 at  1:05pm

Will this fit on top of an ethernet shield? Most don't since the cat5 jack is so large.

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|   Jul 22, 2010 at  2:41pm

tehjrow: Will this fit on top of an ethernet shield? Most don't since the cat5 jack is so large.

Just get the Arduino Stackable Header Kit and use them as spacers between one shield and the next.

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|   Jul 22, 2010 at  3:04pm

That's actually a great idea, thanks for pointing that out!

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|   Aug 16, 2010 at 12:48am

you can get the double wide shield from liquidware...

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|   Jul 22, 2010 at  3:29pm

Am I correct in inferring that, although there are 48 I/O ports, there are only 16 I/O port selections, so that you have to select ports as triads? For example, you can select ports 1, 17 and 33 simultaneously, but not any one of them without selecting the other two and none of them in combination with other ports. (I do realize that just because I've selected a port doesn't mean I have to read from or write to it.)

Also, how much current and what voltages can it handle? There are numerous "Vcc" ports, but I haven't found where it's specified to what they're connected. If it's the regulated 5 V from the Arduino, that'll limit the available current/port substantially. OTOH, if it's the Arduino's Vin, then it's not likely to be a very stable source. Furthermore, it appears it would be useful, for at least some applications (controlling servos, for example), to be able to provide power to the "Vcc" rails around, rather than through, the Arduino.

I'm thinking about the suitability of the Mux Shield to drive large numbers of servos. However, I have yet to do the math to determine how many servo control pulses I can fit in the time between pulses to a single servo.

TIA for you thoughts,
Eric

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|   Jul 22, 2010 at  5:31pm

You can indeed select ports 1, 17, and 33 simultaneously. You can also select only a single channel on only one mux, you don't need to select a channel on all three to operate the mux.

Vcc can handle 2V to 6V because the the IC is the HC not the HCT version. Looks like Icc should exceed 50mA. I can't tell, but it looks like the muxes are getting power from the Arduino regulator.

You won't be able to plug the servo directly into the mux channels unless the servos are very, very, very small (I've never seen servos as small as you would need them).

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|   Jul 22, 2010 at  7:54pm

N8B,
How does one select only one of the 48 ports? I took a look at the example code and found:
//Since all 3 multiplexers have the same control pins, the one multiplexer data line we want to
//talk to should be set to output and the other two multiplexer lines should be be 'bypassed' by
//setting the pins to input

That doesn't appear to support the notion of selecting only one port, just the notion of selecting three ports, but writing to only one of them.

Also, what do you perceive as limitting the size of the servos? AFAIK, the control signal current required by a servo is on the order of 1 mA and essentially independent of the servo's size. The drive power comes from the +V and Gnd wires, so it's not connected to the Arduino's DO. However, the drive power must come from somewhere, which is why I originally asked about the source of "Vcc" supplied to the rows of terminals adjacent to the mux I/O terminals and whether it could be fed other than through the Arduino. (I don't particularly care, in this discussion, about the power going to the muxes themselves.)

As the schematic doesn't appear to be readily available, what's the best way to determine the power routing on that board prior to obtaining one?

TIA,
Eric

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|   Jul 23, 2010 at  1:05pm

Although we do not have the schematic (the manufacturer hasn't supplied one), but we have the datasheet posted for the IC's which will give you all the information you should need.

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|   Jul 23, 2010 at  1:34pm

can you split them up and use this for analog & digital at the same time?

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|   Jul 24, 2010 at  8:17am

Mubo - you can use this as both analog and digital input at the same time. I would start with the analog input example code. If you hook up a switch, you'll simply get a 0 value when off and 1023 when pressed. You can use the map() function to make this into 0 and 1.

int val = analogRead(0);
val = map(val, 0, 1023, 0, 1);

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|   Jul 26, 2010 at  7:19am

Here is a schematic for the shield:
http://mayhewlabs.com/media/Mux_Shield_Schematic.pdf

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|   Jul 26, 2010 at 12:13pm

Mark,

T*H*A*N*X for providing the schematic!

As you can see from my posts above, I'm interested in providing more current through the "5V" and "GND" connectors (to such loads as servos) than the Arduino's regulator can provide. I'd appreciate your help with the following:

1) What are the ampacities of the 5V and GND traces and connectors on the Mux Shield?

2) Can I sever the connections between the rows of 5V and GND connectors and (the connections between the Arduino and the Vcc and Gnd terminals of the mux chips)? (My thinking is: I could run the mux chips (& the reset button & on-board LEDs) from the Arduino's regulator, but use some other power source for the rows of voltage and ground connectors that run alongside the mux terminals. I would need to feed the rows of connectors from that external power source, tying the grounds of the two supplies together to ensure a common reference.)

3) If I can provide a separate power supply to those rows of connectors, can I do that at a higher voltage than 5V? (I'm not looking to get anywhere near line voltage, but I can foresee uses for things in the range of 6V to 24V.)

4) If I can't reasonably sever the connections to those rows of connectors, can I feed +5V and Gnd (from a higher current source than the Arduino's on-board regulator) to the Arduino through the Mux Shield?

TIA,
Eric

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|   Jul 26, 2010 at  9:47pm

Eric -

The easy answer is that the Mux Shield probably isn't what you need. The way it is routed and the ICs themselves are not meant for high current draw or independent voltage lines. There are some servo shield designs out there, like one from Adafruit. There are also multiplexer ICs that are meant to run high intensity LEDs or servos that you might think about.

Let me know if you still can't find what you're looking for and I'll come up with a new shield for you.

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|   Aug  6, 2010 at  7:15pm

I have another shield that is currently using digital pins 2, 3, and 4 - how difficult would it be to make this shield use pins 5,6,7 and 8 instead of 2,3,4 and 5?

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|   Aug  7, 2010 at  7:35am

dgarcia42: I have another shield that is currently using digital pins 2, 3, and 4 - how difficult would it be to make this shield use pins 5,6,7 and 8 instead of 2,3,4 and 5?

It shouldn't be too hard. It might be possible that you can use pins 2-5 for both shields in an ingenuous way since the Mux Shield only uses these pins for control lines during an analog read (if your not in the middle of an analog read, it makes no difference how the lines are used or what data is on them). But, if you want to remove the conflict in hardware, here is how:

Cut the stackable header leads on the Mux Shield pins 2-5 so they don't connect to the Arduino. Run jumpers from pins 5-8 on the Mux Shield to pins 2-5 on the Mux Shield. Change the example code to the following:
#define CONTROL0 8
#define CONTROL1 7
#define CONTROL2 6
#define CONTROL3 5

This way you are isolating the Mux Shield from the Arduino and still getting the Mux Shield the data it needs.