How’s everyone? It’s been years since I’ve visited – sorry!
A classmate of mine is working on their Senior Project and needs some advice on servos.
Short story is they’re building a sun-tracking umbrella. They will be mounting an umbrella to a pan-and-tilt thingie which will be controlled based on readings from an array of LDS sensors.
The Umbrella will weigh between 5 to 9 oz, and may contain as much as .5-1.5lb of solar panels on top of it (design may change). The shaft between the top of the umbrella and the tilt bracket will be roughly 5-7 inches. I recommended the HSR-5980SG servo, as it seems to have enough torque for the task… though I’m not sure how much overkill it will be. The servo needs to withstand load from wind blowing on the umbrella, as well as the weight of the umbrella itself. Does the Pan as well as the Tilt servo need to be beefy, or can you get away with one high-torque servo and one cheaper servo?
Also what is the current draw of the servo? The specs say (for 6v) that it’s 300mA w/o load and 4.2A under stall. With a 50% load (of max torque) will it consume ~2A, or what?
It’s been a long time since your last visit… And finally, you’ve passed 1000 posts!
I don’t think you’ll need very high torque servos since a sun-tracking device wouldn’t need to move very fast. I think 2x645 coupled to a relative high ratio geartrain could be used. Check out servocity and you’ll find pan and tilt systems that might work.
I completely forgot about the gearboxes servo city sells! Unfortunately, it seems a pan + tilt module with servos still comes out to $200 or so… though it can easily handle 5 lbs which is nice. It doesn’t seem the Medium-duty pan system is in stock anymore, as the page doesn’t work . The cheaper pan & tilt unit is $40 but doesn’t include any servos or gearing.
KM6VV, which pan/tilt unit from servo city did you use?
as you will only require a small a small amount of movement speed and travel you can use a lower torque servo for the pan. i would even go as far to say you’ll get away with using hs485 servos for tilt too.
@ innerbreed - You think the lynxmotion pan & tilt brackets with a 645 or 485 would be enough? That would definitely cut down on costs! From my calculations 1.5lb * 7 inches = 189oz-in. That’s significantly more than either one of those servos can provide. I can see how they might still be able to move slowly, but wouldn’t the servos jerk when holding a position? They would also draw a lot more current under full load, right?
yes it would seem we would need to see how you invision it to look. the way i see it is that the pan could be house in this
with space for your electronics too…
i was thinking the pan servo wouldn’t be under much as its shaft it upright… right?
do you have a drawing?
i suppose a 645 will do for the tilt. may need to use some form of support. ie passive hinge or springs.
Basic idea is there will be a ~5ft PVC/Steel rod which will be connected to the side of one of those folding beach chairs. On top of the pole will be the pan/tilt system. Connected to the tilt bracket will be the umbrella, which will slot into a 3" tube and hub connector lynxmotion offers. Note that the drawing is not to scale.
does no one use pen and paper anymore. lol.
quick simple and to the point i might add.
IMHO i would use:
645 for the tilt and a 485 for the pan: low end design.
Using standard servos and brackets won’t work under hard wind though. Maybe some sort of wind sensor device with either an alarm or a signal to the main mcu that cut the power (no pwm signal for analog servos) to the servos if the wind is to hard. Or a device that fold the umbrella, but that would just add more weight…
And finally, you’ve passed 1000 posts!
. The cheaper pan & tilt unit is $40 but doesn’t include any servos or gearing.
