Running multiple servos at the same time?

kinetical

Hi,

I'd appreciate your advice with this question. I want to run three servos at the same time, each with their own routine. All the program examples I have looked at have them going one at a time. Can someone point me towards an appropriate help file or something?

Thanks,

Tracy

erco

You have to weave them all together in an efficient, continuous loop, along the lines of:

a: pulsout 1,nnn' servo 1
pulsout 2,mmm' servo 2
pulsout 3,ppp' servo 3
pause 20
goto a' loop back

and the rest of your program has to be "minimally invasive" to that loop to keep the 3 pulse streams going strong. You may have to decrease the pause 20 if you have a lot of operations going on.

erco

If you're a software guru or minimalist who likes a good challenge, weaving multiple pulsouts into a magnificent tapestry of code is fun. A symphonious software string of poignantly and properly-placed pulses to succinctly station several servos. But if you ain't a software person, or you want to get even more servos going, consider a Parallax hardware alternative, the ServoPal:

http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/servopal/List/0/SortField/4/ProductID/481/Default.aspx

You send a single pulsout per servo, and the ServoPal endlessly repeats the necessary regular string of pulses to get it to or hold that position. One ServoPal can control 2 servos.

Plus, it has an extra alarm function so that Br'er Whit won't burn his biscuits anymore.

RobotWorkshop

Another option is to "offload" the task to another device. Parallax has a couple of options for this:

ServoPAL - Item code 28824

http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/servo/List/0/SortField/4/ProductID/481/Default.aspx

Propeller Servo Controller USB - Item code 28830

http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/servo/List/0/SortField/4/ProductID/595/Default.aspx

With either of these you just tell them what to do with the servos and avoid the whole issue of having to constantly update the low level servo pulses over and over again.

Robert