XK-1 Development Kit + ADC

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daleonpz
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XK-1 Development Kit + ADC

Postby daleonpz » Thu Nov 04, 2010 1:24 pm

I have bought XK-1 Development Kit and I am going to control six servomotor so I need to use, I guess, six ADCs (for my sensors - Potentiometers ) ;thus I m asking you which ones I should use. In addition, I am worried about the number of I/O ports due to XK-1 has 24 and it means that I can only use 4 ports per motor.

this is the servomotor I've got :
http://www.servocity.com/html/1010_lbs_ ... actuat.htm
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Andy
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Postby Andy » Thu Nov 04, 2010 2:08 pm

If your sensor is just a pot then something relatively low performance like the AD7997 should work:

http://www.analog.com/en/analog-to-digi ... oduct.html
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bsmithyman
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Postby bsmithyman » Thu Nov 04, 2010 5:10 pm

daleonpz wrote:I have bought XK-1 Development Kit and I am going to control six servomotor so I need to use, I guess, six ADCs (for my sensors - Potentiometers ) ;thus I m asking you which ones I should use. In addition, I am worried about the number of I/O ports due to XK-1 has 24 and it means that I can only use 4 ports per motor.

this is the servomotor I've got :
http://www.servocity.com/html/1010_lbs_ ... actuat.htm
Wow, those things are terrifying...
Many ADCs have multiplexers on them (e.g. they can read from multiple sources), so depending on how far apart the servos are going to be, you could use a 6- or 8-channel ADC. If you want to put the ADC chips closer to the actuators, and go all digital, you could always use I2C, which only requires two I/O lines to talk to all of the ADCs combined. With an actuator like that you're not going to need high performance ADCs.

It looks to me like the drive is 12V up to 17A. You could do that a few ways; the simplest would probably be a half-bridge, in which case you need 2 I/O lines per actuator (one for direction, and one for power/PWM). For that matter, you could use I2C for that as well (e.g. with an I/O expander) and gain some isolation from the servo driver board. That would take you down to 2 I/O lines for the whole thing.

I'm not saying that's necessarily what you want to do, but if you get tight for I/O there are always options.

Cheers,
Brendan
daleonpz
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Postby daleonpz » Fri Nov 05, 2010 4:39 am

bsmithyman wrote:
daleonpz wrote:I have bought XK-1 Development Kit and I am going to control six servomotor so I need to use, I guess, six ADCs (for my sensors - Potentiometers ) ;thus I m asking you which ones I should use. In addition, I am worried about the number of I/O ports due to XK-1 has 24 and it means that I can only use 4 ports per motor.

this is the servomotor I've got :
http://www.servocity.com/html/1010_lbs_ ... actuat.htm
Wow, those things are terrifying...
Many ADCs have multiplexers on them (e.g. they can read from multiple sources), so depending on how far apart the servos are going to be, you could use a 6- or 8-channel ADC. If you want to put the ADC chips closer to the actuators, and go all digital, you could always use I2C, which only requires two I/O lines to talk to all of the ADCs combined. With an actuator like that you're not going to need high performance ADCs.

It looks to me like the drive is 12V up to 17A. You could do that a few ways; the simplest would probably be a half-bridge, in which case you need 2 I/O lines per actuator (one for direction, and one for power/PWM). For that matter, you could use I2C for that as well (e.g. with an I/O expander) and gain some isolation from the servo driver board. That would take you down to 2 I/O lines for the whole thing.

I'm not saying that's necessarily what you want to do, but if you get tight for I/O there are always options.

Cheers,
Brendan
Actually, it was my basic idea, but rightnow i dont know where Im going to place my PCBs and thats a problem due to i wanted to design a Real Time control. Well... anyway, I've got to check it.

by the way, I want to do a stewart platform control design.

Thank you!
:ugeek:

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