RoboSavvy Forum

Pressure sensors on the feet

2007-07-06T11:55:31+01:00

I got the number 7 from doing some simple experiments. If you're polling at high frequency, and you log this information on the PC, the pattern is obvious.

- Jon

Statistics: Posted by JonHylands — Fri Jul 06, 2007 11:55 am

Pressure sensors on the feet

2007-07-06T09:09:17+01:00

JonHylands wrote:
The load values from the servo are only updated seven times per second

7 times per second is not much... but still it shoud be enough to give a "touch" feedback.
Where did U get this info?

JonHylands wrote:
The load value is really just the amount of current the motor is drawing, which varies wildly when the joint is moving.

...sure, but the servo of the foot has almost not load when the leg is raised (the ankle instead has to stand the weight of the leg)... so monitoring the foot's joint you should be able to see an evident increase in current when the weight is shifted on that leg.

I'm gonna try this soon but I am currently working on the exapod which has no feet unfortunately

Statistics: Posted by Zypkin — Fri Jul 06, 2007 9:09 am

Pressure sensors on the feet

2007-07-05T17:03:56+01:00

The load values from the servo are only updated seven times per second, and they include both the external load from balance as well as the load imposed by the motor. The load value is really just the amount of current the motor is drawing, which varies wildly when the joint is moving.

- Jon

Statistics: Posted by JonHylands — Thu Jul 05, 2007 5:03 pm

Pressure sensors on the feet

2007-07-05T14:23:27+01:00

I've played around with load values and they just are not very sensitive IMO. I still need to do more experiments though.

Statistics: Posted by billyzelsnack — Thu Jul 05, 2007 2:23 pm

Re: Pressure sensors on the feet

2007-07-05T12:29:17+01:00

Jon, what U did so far with this pressure sensors is interesting... but... isn't it easier just to read the load from feet's dynamixels???

I didnt try yet but as soon as the foot is charged you have a change in the load/current in the servo... so... why dont use it?

Statistics: Posted by Zypkin — Thu Jul 05, 2007 12:29 pm

Pressure sensors on the feet

2007-05-08T12:13:12+01:00

Great! I'll wait to take 2 or 3 of them

Statistics: Posted by Goldrake — Tue May 08, 2007 12:13 pm

Pressure sensors on the feet

2007-05-08T04:57:21+01:00

Here's an update on the foot pressure sensor boards:

and here it is, mounted:

The pressure sensors will need extension cables (which I will supply as part of the kit).

- Jon

Statistics: Posted by JonHylands — Tue May 08, 2007 4:57 am

Pressure sensors on the feet

2007-04-30T19:15:19+01:00

Thank you for the answer. Nut on my board i have only 6 pin for A/D. So i need an "expansion". I should do a little board with a micro that can convert A/D and send me result on GPIO. Any ideas?

Statistics: Posted by Goldrake — Mon Apr 30, 2007 7:15 pm

Pressure sensors on the feet

2007-04-25T18:56:16+01:00

I have a few new boards, ready to be populated.

On the left is my original prototype, which works, although it has a couple issues. On the right is my new board, which I haven't had a chance to populate yet.

I've been just crazy busy for the last few weeks, and have had very little time to put towards this board or the IMU board. I'm planning on getting the first 10 IMU boards populated this weekend, so hopefully I'll have some good news next week.

To answer your question, you feed one pin from the sensor into an A/D port of a micro-controller, with a pull-down resistor (10K). The other pin of the sensor gets +5 volts.

- Jon

Statistics: Posted by JonHylands — Wed Apr 25, 2007 6:56 pm

Pressure sensors on the feet

2007-04-25T16:51:39+01:00

anyone knows how could i connect that sensors to a gpio? So from analog to digital. What type of circuit i have to do?
Thank you

Statistics: Posted by Goldrake — Wed Apr 25, 2007 4:51 pm

Pressure sensors on the feet

2007-02-10T13:58:23+01:00

I'd try that UHU contact cement, can't remember the exact name right now. It's available at Michael's and seems to stick to anything.

Harry

Statistics: Posted by HarryBotter — Sat Feb 10, 2007 1:58 pm

Pressure sensors on the feet

2007-02-10T01:41:33+01:00

I'm going to be putting some kind of rubber pad on the bottom of the feet, which will cover up those sensors. The sensors actually stick down below the bottom plane of the foot, so the pad will contact the sensor nicely.

Right now I'm planning on using a silicone pads that I cut out of the bottom of a silicone baking pan I bought ($6.99). The silicone is about 1.5mm thick, wihch is perfect. The only real trick is going to be getting it stuck to the feet - its pretty non-stick. I'm going to try and use some silicone (the kind you get out of a tube), and rough up the surface of the pad so it will stick better.

- Jon

Statistics: Posted by JonHylands — Sat Feb 10, 2007 1:41 am

Pressure sensors on the feet

2007-02-10T00:44:00+01:00

Jon. Are you going to put any 'feet' on top of those sensors or will they just be what contacts with the ground.

Statistics: Posted by billyzelsnack — Sat Feb 10, 2007 12:44 am

Pressure sensors on the feet

2007-02-09T23:57:34+01:00

If you can figure something out to simulate decent tactile touch, you can probably write a PhD thesis based on it.

Do yourself a favour - start small, get something working, and then worry about making it better.

- Jon

Statistics: Posted by JonHylands — Fri Feb 09, 2007 11:57 pm

Pressure sensors on the feet

2007-02-09T23:29:52+01:00

I'm searching something that could simulate the sense of tact. Can you suggest me something?

Statistics: Posted by Goldrake — Fri Feb 09, 2007 11:29 pm