We’ve been having problems with the KOP Gyro because of its inherent drift. We’re using the Gyro to assist in climbing, and I’d like to see if any Chief Delphi-ers know of a more sensitive analog Gyro that we could order to replace the KOP gyro.
We’re mainly looking for one that is decently sensitive (within 1-3ish degrees), gives an Analog input (like the KOP Gyro), and doesn’t drift at a standstill (or at least has neglible drift, not the 1-5 degrees/minute we currently are trying to deal with).
Any suggestions?
Before I make any suggestions, I’d like to understand how you intend to use the gyro. I don’t know how it would help with climbing.
Before you go looking for another gyro, make sure you first understand the one you’ve got.
First, all gyros have drift. That’s ok as long as the drift is constant, because you can calibrate for it. Let the gyro sit still and average the reading over a few seconds. Then subtract this value from all the future readings. Note that the drift will vary with temperature, so a lot of sensors will actually include a separate temperature output you can read and use to compensate.
In practice, I’ve found that 1 degree per minute would be really good, and even 5 deg/min isn’t so bad. You might want to zero the gyro before you begin climbing, so that anything that happens beforehand doesn’t matter. Depending on the gyro’s sensitivity, hard slamming or slow movements will cause small errors, and you’ll inevitably end up with some accumulated error.
Sensitivity is a more complex topic than drift. Sensitivity is (by my definition) the smallest motion that you can accurately measure. Since the ADC on the robot controller has a set number of bits, then the sensitivity is inversely proportional to the range. That is, for a 10-bit ADC (which gives 1024 steps), a 300 deg/sec gyro has a precision of 300/1024 = 0.3 deg/step. A 100 deg/sec gyro would give 0.1 deg/step precision. With an analog ADC, sensitivity and range are directly in competition, and you need to think carefully about what you actually need.
Of course, that isn’t the full story to sensitivity. If your sensor is very noisy, then the precision with which you can measure is reduced. For example, if there is +/- 100mV, then with a 10-bit ADC, you’ll get 1024 steps / 5V * 0.1 V = +/- 20 steps. In this case, using a higher-sensitivity gyro will let you get better measurements for small motions that you wouldn’t otherwise get.
Also you could think about combining with an accelerometer. Accelerometers are less accurate but don’t drift. gyros are more accurate but do drift.
You saw 254’s climb, right? They use a gyro during climb to know exactly when to climb to the next level…or so I’ve heard.