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Unread 05-18-2017, 12:19 PM
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Talon SRX Analog Voltage Output

Hello everyone.

My team decided to build an off season swerve drive. The positioning motors are driven by a talon SRX with Talon SRX Universal Breakout Board (am-3281) and an absolute analog encoder. The encoder works on a 0 to 5V scale, but the problem is, even though the srx should be feeding out the 5V from the analog output to the encoder, it is only reaching about 4.4V max. Without any load, its closer to 4.7V. This causes the issue of a cutout on the readings, leaving it hard to hit accurate positions.

My current solution was to just power the encoder straight from the 5V output on the VRM, but I'd like to know if there is a way to ensure complete output from the SRX...

Thanks!
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Unread 05-18-2017, 12:40 PM
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Re: Talon SRX Analog Voltage Output

You should be powering the encoder off the 5v pin on the SRX, not the analog input if that's what you're trying to do. I'm not sure I read that correctly.
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Unread 05-18-2017, 01:33 PM
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Re: Talon SRX Analog Voltage Output

Quote:
Originally Posted by asid61 View Post
You should be powering the encoder off the 5v pin on the SRX, not the analog input if that's what you're trying to do. I'm not sure I read that correctly.
Agreed. The same processor (in this case the SRX) that reads the sensor should provide the voltage reference. You might want to check the resistance of your sensor, wires, and connections; some corrosion might reduce the voltage readings.
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Unread 05-18-2017, 01:51 PM
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Re: Talon SRX Analog Voltage Output

Quote:
Originally Posted by GeeTwo View Post
Agreed. The same processor (in this case the SRX) that reads the sensor should provide the voltage reference. You might want to check the resistance of your sensor, wires, and connections; some corrosion might reduce the voltage readings.
Any loose connections (or really any resistance) will cause a voltage drop. So definitely check your wiring.
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Unread 05-19-2017, 09:57 PM
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Re: Talon SRX Analog Voltage Output

Currently I'm powering from the VRM, because it consitently feeds the 5V. But the SRX analog pinout (Power, signal, ground), isnt supplying the full 5V. Even without the load of the sensor.
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Unread 05-20-2017, 07:53 AM
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Re: Talon SRX Analog Voltage Output

Quote:
Originally Posted by GrizBear View Post
Currently I'm powering from the VRM, because it consitently feeds the 5V. But the SRX analog pinout (Power, signal, ground), isnt supplying the full 5V. Even without the load of the sensor.
Have you checked the 5V pin with a multimeter?
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Unread 05-20-2017, 08:20 AM
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Re: Talon SRX Analog Voltage Output

This is on the last page of the SRX Universal Breakout User Guide:
Quote:
Originally Posted by MACH Engineering LLC
I/O on the Talon SRX Breakout can be set for 5V or 3.3V as required, with 5V being default. However,
the Analog Input to the Talon can only read up to 3.3V. If a 5V sensor is used (such as MA3 Absolute
Encoder), resistors must be changed to read the sensor’s full scale output. The recommended change is
to solder a 43.2kΩ (1% 0805) resistor into C2, and replace R6 with a 22.1kΩ (1% 0805).
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Last edited by pilleya : 05-20-2017 at 08:22 AM.
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