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Hi Guys — I'm a developer and I want to have a bit of fun with electronics. I don't know much about it so I have a bit of a question. I'm pretty sure this can apply to Netduino, Arduino or any other one.

I want to use the Netduino like if it was variable resistors.

I would connect the Netduino to a helicopter remote control by removing its variable resistor from the remote's board and connect Netduino's output.

The question is how can I do that? How can I wire it and do I need additional components?

Some Links/Pictures

http://sharetext.org/C3PS

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2 Answers

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You can use a microcontroller to control a digitally-controlled potentiometer... there are lots to choose from. They vary in their control mechanisms, but there are several available that can be controlled over I2C or SPI.

The MCP4151-103E/P looks to be cheap, through-hole, pretty capable, and is controlled over SPI for instance.

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I looked at the digital potentiometer and the data sheets. I only half understand it. They're eight pins on this thing. Which pins would be connected to the remote control (three pins I presume?) and which would be connected to the netduino/arduino? I guess I would need four of the chips (or two dual?) to control the four different variable resistors on the remote. – iDev247 Jan 26 '12 at 8:20
@iDev247 not sure I understand your question. You get one (or two) variable resistors per chip that you can use as potentiometers or rheostats. So yes you would need more than one chip to replace four variable resistors. – vicatcu Jan 26 '12 at 18:05
@iDev247 As for what you connect to the Arduino, that would be the /CS, SDI, SDO, and SCK. These are the SPI interface (a standard serial interface) - which the Arduino has corresponding pins for and a software library using. If you can draw a circuit that includes your existing variable resistors replacing them with the digital ones should be a straightforward pin mapping exercise. – vicatcu Jan 26 '12 at 18:07
up vote 2 down vote

Instead of trying to make the microcontroller to act like a variable resistor, you should find out what are the results of the variable resistor? In this case the variable resistor is most likely used to control the voltage on a pin of some component. Find out what the voltage range is. Find out what the current is.

A lot of microcontrollers have on-chip DACs that can output from zero to supply voltage. If the expected voltage range is inside the output range and the expected current is lower than the output current (written in the datasheet of the MCU) then you can connect them directly. Otherwise you will have to use an opamp to amplify and/or offset the voltage (or a transistor to amplify the current, or both).

On the other hand, if you wanted to make Netduino behave like a variable resistor so you could use it to control volume it would be much more difficult (or you could just use a digital volume control chip).

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Thank you. I will research a bit. Will try to find out what it's controlling (which voltage and current). – iDev247 Jan 26 '12 at 8:18

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