My best guess without further clarification would be to use opto-isolators.
Not really sure what you are talking about here or what you are trying to achieve. Is this a real car, an RC model car, a PC racing simulator set-up? What task do you want an Arduino to perform? Mimicking key presses from those 5 switches near the top-right of your diagram? What voltages are in those wires?My best guess without further clarification would be to use opto-isolators. Duplicate the 5 resistor values (strange values, by the way, very precise down to 1 ohm) and mimic the switches with 5 opto-isolators driven by 5 Arduino pins.
The resistor values are copied from the (SMD) resistor marking- 68 Ω, 120 Ω, 1k8, 300 Ω, 510 Ω. I suspect the "182" is an error.
A set of reed relays or signal relays could be used of course, but to do anything smarter requires reverseengineering how the existing unit senses the resistances - with constant current? with a resistor divider?what voltages relative to ground does it use/assume?
Can you measure the current flowing when switch 5 is closed ? You should then be able to calculate the unknown resistor in the divider.Edit:Or probably easier, measure the voltage drop between the points marked ADC and GND when switch 1 is closed.
Hi,I take it that you will only have your emulation circuit connected and the real world circuit disconnected?As you are working with car computer and unknown currents, can I suggest KISS.Use small relays as the switches.That way YOUR control system is isolated from a VERY EXPENSIVE control system.Tom....
Hi,No the two systems will interact.When your arduino output is HIGH on say D0, that will pull the 68R HIGH, when it is LOW it will gnd the 68R.The Arduino outputs are HIGH/5V or LOW/gnd.You are assuming the LOW is open circuit like the switches.OFF is not float it is a digital level, in this case gnd.Tom... Like I said KISS.
So how are you going to match the Arduino supply voltage to the mcu supply voltage?
FWIW, if you persist with this folly and you're using an Uno/nano or similar, don't use D0 or D1. Already in use.
Maybe put a diode on the output of the Arduino resistor ladder so it protects from any getting any backfed voltage.
Nothing foolish, I was just trying to see if any other alternative than slow bouncing emf generating clicky relays.
I have a steering wheel control that I need to control with an Arduino. Coding is not an issue but I am wondering what is the best way to "inject" keypress into the Instrument Cluster ADC 5V signal.Any ways to keep the steering buttons working at the same time (must not affect line resistance) ? Digipot? DAC ?