What sensors make sense on a simple gripper arm?

I just purchased a dagu MkII gripper,  and am making a 5dof arm for it.  I do not have any experience whatsoever with operating a robotic arm/gripper.   What sensors make sense on this?   I know servo feedback for grip force, but does a gyro or accellerometer make sense?   I can visually see the full range of motion with the Raspberry Pi cam, but would feel better if there was some way to gaurantee "level".... 


I've searched this site, and cant find much other than pressure sensors or cameras on the grpper.




All I need is just one more toy...

I wonder if just reading the internal pot

would be sufficient to know if/when the servo has stalled. Cheaper and easier(?) than adding more hardware. As for level, what about some kind of simple tilt sensor? If you are already reading the pot, you could probably avoid the tilt sensor and just have a homing routine for the servo at each start up. Maybe check if the gripper is open before rotating?

If you are always going to

If you are always going to want the gripper to be level, connect from the arm to your gripper (instead of a servo just have a hinge with a connect from the arm to your gripper) so it will always be level.  Sorry, not explaining it very well.  


shows a picture of how to make the arm level.  Click on the starting video, and they show what I mean.  




Yes, I think this is similar to whats on the Dagu Service Droid

There’s a name for that mechanical arrangement.  Back hoes and Bull dozers use it to keep buckets and blades level.

I’m sure OddBot is banging his head right now saying “Why didn’t you just buy a service droid?”


Oh well…  plugging on.


Thanks for the direction.


And this is why I put the question out there…

I didn’t know what I didn’t know…    Quite honestly, I bought the arm and servos on a whim.  The wife said “I’ll be impressed when it can bring me my wine!”   She didn’t say that it couldn’t be 3-4 oz in a plastic cup!?


So… When not used, all five servos will be “parked” ie: the arm will be tucked into a known position in front of the bot. So I “think” that my point is almost moot.

If I know my starting point, i should just be able to use math to plot the arc’s while it’s traveling.

NHBill below had suggested using a double pivot arm to maintain level.  I’m still toying with that idea as well.

KISS is the word of the day…



I figured there had to be a

I figured there had to be a name for it.  Sorry for being so vague; it is hard to describe.

The SD is nice and a cool design (I bought one for my son for Christmas with a Rover 5).  But it is also fun to build something too.  On my present project, I have been using aluminum U channel ($10 for 8’ section at HD) for the arms and small Lazy Susan bearings for the elbow, wrist etc.   You can cut aluminum on a tablesaw or chopsaw, it is light and strong and easy to drill holes into so it is relatively easy to work with.  Just an idea on what to do for arms with the gripper.  I will be posting over the next few weeks to show what I have built.

I am sure you will find something to do with the dagu gripper.  As always, I look forward to seeing what you come up with.







Flex sensor



Some bots have a camera on
Some bots have a camera on their hand, so it could see what’s it picking up.

I’ve got the Raspberry Pi Cam on a pan/tilt just above

It is able to see almost the whole range of motion of the arm.