Do you have a question on MEMS Sensors? Ask our Expert, Donna Sandfox

hello donna, im looking for a particular sensor and would appreciate your experise. Specs, needs to be at least 9 feet , prefer a photo reflector, it also needs a sesitivity adjust right on the sensor or a time closed delay, 24v DC, there is alot of dust in the air in this application, fabric particles, we cant have the sensor false tripping. Would also prefer a quick connect for easy replacement. I have no access to the program of this machine so i plan on wiring it in series with the E stop curcuit to power the allen bradly micro logix. Thanks for your time and have a nice day.

Hello Donna,

Is it possible to calculate constant velocity with the help of an IMU? I am working on a school project in which i have to trace the path of a toy car, so i had thought of the idea of doing it with IMU, microcontrollers and a display and i am stuck at this point...Please help me asap, i have to submit my project in the coming week ....

This issue was discussed in a recent thread on E14 which you may find helpful:

http://www.element14.com/community/message/90851#90851/l/re-arduino-uno-lsm303dlm

The short answer is that you can only estimate velocity by integrating acceleration over time and that gives errors which increase over time. The system errors can be constrained by resetting the velocity frequently. On a toy car you would do much better to look at wheel revolutions (take care to deal with corners, wheel spin etc). If you have the processing power and the maths/software capability you can combine the signals from a 6 DOF IMU (Degrees Of Freedom, Inertial Measuring Unit) with signals from 4 wheels and make a much better estimate.

MK

Hello Justin,

What's missing from your question is WHAT you need to sense.

Also: does it need to be MEMS?

its going to be used in a paintroller beveling and trimming machine, there is an 8 foot shear right above the "carder", basically a giant brush that rotates very quickly. Recently the carding material un raveled and got cought up in our shear causing thousands of dollars in damage. So i need the circuit to open when the it senses this carding material begining to unwind. Not an MEMS. thanks again for your time.

Hi -

I am using the LIS331 DLM accelerometer to measure acceleration in a moving vehicle.  I understand the device has acceleration outputs for the 3 axis, x_hi, x_li, y_hi, Y-lo, z_hi, z_lo which represent 16-bit 2's compliment numbers for the acceleration with x_hi being the high order byte and x_lo being the low order byte.  When the accelerometer is at rest, the values read from these outputs are very large. What unit are the output numbers in?  Are they displaying acceleration in m/s/s? There is a user selectable scale of +- 2g/4g/8g.  How should this scale be applied to the acceleration output values if at all?

Thanks,

Alan

Alan, may I suggest (nicely) that you read the data sheet again. I haven't studied it (Doc ID 15102 Rev 4) in detail but it's clear on page 1 that the readout is 8 bits. Further peeking shows that there are no registers called anything much like x-hi. The readout registers are called OUT_X, OUT_Y and OUT_Z (page 3 and page 30).

Have another look and ask again.

BTW how are connecting to the device and reading it's registers.

MK

Hai Donna,

  http://uk.farnell.com/prowave/fs-2513p/sensor-piezo-film/dp/1007374#similarProducts

This is the pressure sensor which we gonna use for our application for sensing pressure from the cheek

developed by tongue. By this sensor, can we accomplish our sensing requirement ??

Waiting for reply,

Thanking you,

K.V

No, this is not suitable. It does not give pressure, it measures vibration, and then not in the DC-range.

You might want to look at sensors by Tekscan (not available through Farnell)

By the way, this is not a MEMS sensor

Hi Santosh - we developed a 3D MEMS sensor that measures motion with a 3-axis accelerometer, gyroscope, and accelerometer - so it provides 9 channels of data. It has its own microprocessor, power source, and can communicate with any bluetooth or analog system. We needed it to develop an electronic personal trainer. Let me know if you're interested - I think it could help you out with your respiration measurement challenge.