Hi, I’m running a Bot and Atom Pro 28. I’m trying to setup the servos on a Hexpod 3R … so I’m looking for the mid position of the HS-475HB servo. I send a pulse to the servo and it moves… but it’s doesn’t look like it’s the middle of the rotation… it seems to be closer to the end.
I’m using
pulsout p0, 1500
pause 20
Should a pule of 1500 be smack in the middle of the rotation? Or so I have to include and offset? If I add +800 to the pulse ie.
pulsout p0, 1500 + 800
it seems to be more in the middle… then I losen the output wheel and move it etc.
But this just doesn’t seem right… when 1500 should do it?
Are you sure about that? Of the 21 servos I have used so far on my hex, they all have 1500 as center. That’s three differrent models from two different brands.
i run the same mid posn program on a bot board and it sets my mid posn all the way clockwise. i also tried it at 750 and there was no difference. what’s going on? my batteries are charged, my jumpers are set, maybe its got something to do with being in the southern hemisphere? anyone?
Um, maybe on newer or a digital $ervo but on a standard analog servo (specifically I use futaba in planes) the frame rate will influence the position. They used to just rectify the signal in the servo so changing the frame rate is equivalent to changing the duty cycle. I checked with another EE here who has also designed systems controlling rc and industrial servos and this is what he recollects as well. On the other hand if newer analog servo amplifier designs have changed to some sort of pulse width locked loop design in the servo amplifer maybe it works the way you describe.
OK, I resubmit that the frame rate does not appreciably effect the servos output shaft position. Especially in the contect of this thread. What I was referring to is that the pulses on time is what is used to command the output shafts position. The frame rate my have some influence on the final position, but it’s not designed to do this as a control method. okie?
yep i ran the program in the tutorial written by beth frye and the one suggested by head honcho (without the ‘low p0’ at the top) and still the same. the servo posn goes just short of full right. i have hi-tec hs-422 servos…and am running two battery packs in series
If you’re using an Atom you must put the low p0 in there. It makes sure the servo pulses are low/high/low. Without it the pulses usually revert to the high/low/high output which will cause the servo to move full right. It does this because it is seeing a 20mS pulse. This is out of range, but the servo still tries.
Yes, any Atom controller requires you set the output pin the the desired level before sending pulsout commands to that pin. It can be done once at the top of the program.
am running the basic atom, with the low p0 code, have applied vs jumper to the first i/0 bus p0-3 (i.e not the +5v dc jumper configuration - ref. abb manual - p.2)., the pulses are generated and the servo resists turning, but still sets mid posn full right.
Please submit the code you are running. Also please tell us again, you’re using the Atom 28, not the Atom Pro correct? Do you have another servo you could try?
okie?