Analog Gyro

[ftc3543]

I am helping an FTC team that uses this Analog gyro robotshop.com/en/300s-single … ensor.html and got a few of technical questions.

]When connecting this gyro to the Modern Robotics Core Device Interface Module, they connect to one of the 5V Analog Input ports. According to the downloaded schematics, this gyro has two outputs: Vout and Vout_X4.7_Inv. Looking at the schematics, it seems the Vout output is max’d out at 3.3V. Is this correct? This output is then fed into an OpAmp that will give an output max’d out at 4.7V?/:m]
]The spec says the gyro’s output has a sensitivity of 0.67mV/degree/sec. Is this sensitivity applied only to the Vout pin?/:m]
]What is the sensitivity if connected to the Vout_X4.7_Inv? According to the spec, this is an inverted output. So I am assuming the voltage will increase when turning anticlockwise whereas it will increase when turning clockwise using the Vout pin?/:m]
]What are the “resting voltages” (i.e. when the gyro is sitting still) on the Vout pin as well as the Vout_X4.7_Inv pin?/:m]
]What are the sensitivities of the gyro on Vout and Vout_X4.7V_Inv pins?/:m]
Thanks.

[scharette]

Hi,

Here are some answers to your questions:

@ftc3543

When connecting this gyro to the Modern Robotics Core Device Interface Module, they connect to one of the 5V Analog Input ports. According to the downloaded schematics, this gyro has two outputs: Vout and Vout_X4.7_Inv.

Yes, it does have two outputs. The Vout is the regular, not-amplified output. The Vout_X4.7_Inv is an amplified signal (gain is 4.7) and is also inverted.

@ftc3543

Looking at the schematics, it seems the Vout output is max’d out at 3.3V. Is this correct?

Well, since the device runs on 3.3 V DC, yes, that would be its maximum output.

@ftc3543

This output is then fed into an OpAmp that will give an output max’d out at 4.7V?

No, it is not. The output from the amplifier is multiplied by a gain of -4.7. (This is written at the bottom of the schematic, under the diagram itself).

@ftc3543

The spec says the gyro’s output has a sensitivity of 0.67mV/degree/sec. Is this sensitivity applied only to the Vout pin?

Yes. That is the “raw output”, that is, unmodified. The Vout is that output.

@ftc3543

What is the sensitivity if connected to the Vout_X4.7_Inv?

It has the same sensitivity, but the output is multiplied by the gain. Therefore, it would be roughly 0.67 mV/degree/s x 4.7, or just about 3.149 mV/degree/s.

@ftc3543

According to the spec, this is an inverted output. So I am assuming the voltage will increase when turning anticlockwise whereas it will increase when turning clockwise using the Vout pin?

Yes, that would make the most sense.

@ftc3543

What are the “resting voltages” (i.e. when the gyro is sitting still) on the Vout pin as well as the Vout_X4.7_Inv pin?

The output of the Vout is proportional to the current rotational velocity. If the velocity is zero, the output would most like be 1.65 V DC. This has to be confirmed with the manufacturer. In many circuits where the analog output can shift in both directions, it is common to shift the resting voltage to the mid-point of the power supply voltage (3.3 V DC, in this case). If this is the case, then the Vout_X4.5_Inv range would be [0.7053, 2.5947] V DC.

@ftc3543

What are the sensitivities of the gyro on Vout and Vout_X4.7V_Inv pins?

See the answers above. The sensitivity is 0.67 mV/degree/s for the Vout output and 4.7 times that for the amplified output.

We hope this helps. We will confirm with the manufacturer the resting voltage and post again once we have more information.

Sincerely,

[scharette]

Hi,

Here are some clarifications:

*]Concerning the Vout at rest:

@manufacturer

Vout at resting is 1.35 V according to datasheet. Yet due to the characteristic of Gyro, the output will drift over time and also temperature. We advise to measure the output voltage at resting.

/*:m]
*]Concerning the full analog output range:

@manufacturer

Maximum angular velocity it can detect is ±300, so if multiply with 0.67 mV = ±0.201 V for Vout. As for the X4.7V output it is differential to Vref: (1.35 V) x 4.7 = ±0.9447 V

/*:m]
We hope this helps understand this sensor board better.

Sincerely,