Long time lurker and arduino fiddler, but my first time posting here. Hopefully someone can point me in the right direction of my next project.
I'm fitting a set of OEM Volkswagen dynamic dampers which have a solenoid built in which controls the flow of oil within the damper, rather than magnetising iron filings which some other dampers use to change the damping rate.
There's some information here: http://www.my-gti.com/2653/volkswagen-dcc-adaptive-chassis-control-design-and-function
Essentially, in it's basic form, i need to be able to control 4 0-2 Amp outputs from the arduino, comfort mode is 0.24Amps, sport mode is 2Amps and normal is anywhere in-between. Failsafe is 0Amps.
I've been doing some looking around, nothing seems to come up with regards to controlling current from the arduino, i've looked at the motor controllers, and whilst some suggest 2amp max eg LN298N it doesn't seem to give any indication that it's regulated to 2amps, or that's the maximum the chip will take before overheating.
Hopefully someone can shed some light on my idea.
Thanks in advance.
You could build some electronics to do exactly what you want, but I'm wondering if that's what the existing electronics in the car does.
Most modern power supplies etc are "switch mode" or "switching" power supplies, which regulate the voltage (or current) by switching the power on and off very quickly (hundreds or thousands of times per second), using the duty cycle of the on versus the off time to determine the actual amount of voltage or current produced.
If this is the case with your electrically controlled dampers, then perhaps you could use a power FET and the PWM output of the Arduino to control the amount of power / current being fed to the dampers.
If however they truely need linear control, it gets a bit harder.
Firstly the Arduino doesn't have any true analogue outputs, its only got PWM, so you'd either need to use a low pass filter arrangement to convert the PWM to a voltage or use an external Digital to Analogue Converter (personally I'd favour an external I2C or SPI contolled DAC).
You could then use the voltage from the DAC to control a power transistor (normal bipolar or FET). But I suspect you'd need some sort of feedback to determine how much current is actually being taken.
So you can either use a low value series resistor and monitor the voltage, or personally I favour the new Hall Effect current sensor modules that you can buy, that have a DC voltage output, and have very low resistance, e,.g. 1milli ohm
If you read the voltage from the current sensor back into one of the analogue inputs, you can do a closed loop control system using PID to give the dampers the precise amount of current you desire.
Anyway, Good luck with the project as it sounds like an interesting one.