[quote=“Scott@FP"]The pullup is the 10K resistor 'C'. With the switch open, the ECU input pin sees B+ voltage. With the switch closed, the ECU sees 0v (or very close to it).[/quote]
the_bluester wrote:To expand a little. You will find that the input impedance is quite high (Point E) and with the switch on or off the current involved is negligible. I suspect that the input will be effectively open circuit when the switch is off, and even if you had grounded inputs for all 16 fixed inputs the total current being switched (with 10K Ohm pull up resistors) will be about 2 milliamps.
The input switches based on voltage rather than current.
Thanks guys, I now understand the workings of the native input switch a bit better. Admittedly I’m a complete novice when it comes to electronics and wiring so I’m in a bit of a learning phase.
[quote=“adrian"]What exactly is it that you are trying to do/find out?
Scenario A is roughly right, there will be a very small current flow (micro Amp range) through some of the additional circuitry on the board. The ADC simply measures the voltage at the pin and that is then used in the logic programmed via PDM Manager.
The easiest way to switch an input is directly to 0V, the internal 10k pull up resistor then gives you the two required states. You can also switch directly to the battery or another voltage source up to 51V. The only issue is because of the internal pull up resistor when you open your switch the pin voltage stays high. That is why you need a 1.5k pull down resistor. So your 12V input should be more like this:[/quote]
Thanks Adrian, your schematic is very helpful. This covers #4 in my second post above, correct? How does #3 differ from #4, or are they the same?
Any chance you could give an example for the need of a "standby current” as noted in #2?
Here’s my project:
viewtopic.php?f=42&t=3450As I mention in that thread, I’m going to be doing a bit of a sleeper install while attempting to utilize the OEM switches. Some of these will remain integrated with the dash harness, while others will be removed from the harness and converted to simple switches.
The ignition switch used to receive full power to Pin 1 and distribute through the other pins. I will now instead be mapping Pin 1 to 0V and wire discrete Motec Inputs to the other pins.
Some OEM circuits are completed by going to ground, such as my high beam headlights and horn. Some switches send a full 12 volts.
The design objective is to have all OEM switches operational in their traditional way, but also program the keypad to do some of the same work (i.e. start car, flash high beams, etc, )
- 510 Wiring.jpg (840.6 KiB) Viewed 21363 times
Thanks