What sensor do i buy to get the robot to know what way is down ?
Just made a quick searching:
robotshop.ca/ProductSearch.aspx?qs=Tilt+Sensor
Sharp GP1S036HEZ Tilt Sensor
junun.org/MarkIII/Info.jsp?item=78
A three-axis accelerometer is the classical way to do the job. A 3-axis gyro or IMU being about the best. Heli gyros might be useful.
Alan KM6VV
Nice, it was something like this i was looking for
robotshop.com/zct245an-ttl-2 … ter-4.html
Anyone who has any experinace of this ?
that could work.
This is the one I have:
Alan KM6VV
We use this in our BRAT projects to detect if the little guy is standing, or laying on its back or front.
lynxmotion.com/p-606-lynxmot … meter.aspx
In this tutorial…
What chip does it use?
Alan KM6VV
My thinking is this
if you have a accelerometer, or a combined accelerometar and tilt-sensor, the possibility so missinterpetation of the signal is bigger than if i get a clear signal about where down is, so i can “put down my feet” if they are in the air
Ive looked at the 2g accelerometersensor, but i didnt understand it could be used as a tiltsensor allso
I believe it’s this one.
STMicroelectronics LIS344ALH
It’s 3D but this module is only using 2 channels.
The tutorial shows the sensor mounted horizontally with X and Y on the horizontal plane. As an accelerometer it’s signal is perfect as a tilt sensor (when not in motion).
so i guess the differance between this one ant the zct245an-ttl is (a part from the price) the fact that the zct245an can measute tilt “in motion”
LM’s sensor has analog outputs, the ZCT has a serial interface, and sends 16 bytes of data.
Tilt in motion? How do they do that?
Zhichuan Electronics ZCT245AN-TTL 2-axis Tilt Sensor User Guide
Might have explained it, but I didn’t find it on a quick read.
Normally, any acceleration would be vectored in along with gravity. Constant motion would have no acceleration, so you could read the gravitational acceleration, and calculate tilt.
You might want to define what you want other then “down”.
Alan KM6VV
There is also a small enclosed direct contact switch that uses a ball bearing that rolls over contacts, when the bot is standing it’s connected and when it falls over it’s disconnected, programming handles what you would like it to do when connected or not connected.
I found these in a Robosapien toy that Wow wee makes.
But I think that the tilt sensor is much more versatile, put one in each foot, they will tell you with a variable voltage that you have fallen over or are about to fall over and again programming on the bot board can do whatever you want with the incoming signal.
If the tilt sensors X/Y is on the horizontal plane, Example: your bot is walking forward, X = front to back, bot starts to walk down hill, programming says when detecting tilt, backup until level, turn ,go forward again…not the best example but…tilt in motion.
Not so much that, but separate acceleration from tilt. If the 'bot is accelerating, that acceleration appears as a tilt. Simple motion, without acceleration does not add to tilt.
Alan KM6VV
This is what i whant it for
- I want the bot to look for ground moving the leg “down”
- I want the gait to compensate for going uphill/downhill/sidehill
a clean “tiltsensor” (saying for example “you are on your back”) a isnt enough for this, what i need is a inclinometer or something that can give a calculated gravityvector, ie a 2D accelerometer
Maybe a magnetometer? I’m just afraid it can be affected by all the motors and so on.
Check out this 9 DOF IMU sparkfun.com/products/9623
Also a video:
This site look industrial:
sensorsportal.com/HTML/SENSORS/Tilt_Sens_Manuf.htm
Also from sparkfun:
sparkfun.com/products/9372
Less hard on the pocket…!
Zeta, that one was AWESOME
… my need to buy is rising by the minute … but really, maby its too much unnessecesery functions … or maby not… 
Maybe you can take a look at the one i have post.
Does look to do something very similar… without the high price tag