USB Resistors

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USB Controlled Resistors

The other day I was doing a design for a board which had multiple thermistor inputs and controlled some heaters (like 3D-printers) based on the thermistor inputs.  I wanted to run some tests of my control algorithm and realized I needed some programmable resistors which I could control from a PC. Hence the USB programmable resistor board was born.  

This board has 5 digital resistors from 0-100k  using the AD5272 (1024 steps with around 1% tolerance) which are control through the USB interface (as serial com port). 

This board makes a great way to test thermistors inputs or add variable gain control to an op-amp. 

Note the digital resistor inputs are limited to 0-3.3V. 

 

Drivers for the USB serial port are here. On some windows system since the driver is not signed you might need to do the same steps as outlined here to install the driver.

 

Schematics and source code:

https://github.com/Misfittech/USB_Resistors

 

Setting Resistors example:

:>help
help - Displays this message
ohms - set/gets Ohms, example 'ohms R1 50000' to read 'ohms R1'

:>ohms R1 1000
R1 is 977 ohms

:>ohms R2 1000
R2 is 977 ohms

:>ohms R3 1000
R3 is 977 ohms

:>ohms R4 1000
R4 is 977 ohms

:>ohms R5 1000
R5 is 977 ohms