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Discussion and questions related to the course PDM Installation & Configuration
I'm trying to configure my motec keypad to display a red light on one of the keys when the ignition is powered on to show the electric handbrake is applied.
I'm using a motec PDM30 for this. There is an input pin from my electric handbrake controller that provides a 5v feed when the handbrake is on. I've created a function that increases a counter to 1 when the input is above 3v and applied this to the LED3 Channel of the key. The light comes on only when I release the handbrake and then apply the handbrake. I can't get it to come on when I switch on the ignition, and the handbrake is already applied (input is showing 5v when powered on).
I have also tried to set the LED3 Channel to use the 5v input from the electric handbrake but got the same result.
Does anyone have any ideas on how I can get this to work?
Thanks in advance, Trev.
Can you post your config thanks.
Hi, Config attached.
The main issue that sticks out to me is that you have Input.HandBrake.On and Input.HandBrake.Off both triggering in the same manner, so it is possible that they will both trigger at the same time (I'm presuming that they are both wired to the same output from the handbrake controller?) If they are both from the same output, I would remove one of them and rename the other as Input.HandBrake.Status and have it so that if the handbrake is engaged (5v feed from the handbrake controller) then the status is active.
I would then change the operation of the Function.HandBrake.Control to be a condition using the Input.HandBrake.Status = True so that it activates when the input is true.
Thanks, Input.HandBrake.On and Input.HandBrake.Off are separate outputs on the handbrake controller. The Input.HandBrake.Off has not been assigned to the keypad LED's and I don't think I have used it on any logic in the PDM yet (just set it up as an input). This input does only show 5v whilst the motors are realising the brake pads (when the handbrake is fully on or off it is 0v). Therefore I don't think this is the issue. If I monitor the PDM inputs when I switch on the ignition it reports the Input.HandBrake.On as having 5v but no light on the keypad. If I then release the brake, Input.HandBrake.on drops to 0v. I then apply the brake Input.HandBrake.on shows 5v once the motors have applied the brake pads and the light comes on.
It seems to like the keypad is only receiving the signal to apply the light once the button has been used.
Any other ideas?
What it sounds like is that as the signal from the handbrake controller is already high when the PDM powers up, the voltage is not going through the trigger point on the input for it to be switched on. On the PDM the voltage on the input has to go through the active voltage trigger value in the correct direction for it to be detected as active, if the voltage is already over this trigger point it will not be read.
I'll have a think about how to get around this.
Do you know what the supply pin from the handbrake controller does when it it isn't supplying 5V? I am willing to bet that it likely floats, and has no continuity to ground. As the PDM input pins have a 10k pullup to Batt+, the input trigger is not working as expected as the only time the voltage goes low to trigger is as the controller supplies that pin with 5V, otherwise it stays high (as Stephen has already mentioned)
As covered in the PDM user manual, in use cases like this, a 1500ohm 0.25W resistor should be connected between the input, and input 0V. This will help pull the input voltage low when the signal from the controller is not active.
You gave me the answer ! "signal from the handbrake controller is already high when the PDM powers up"... So I added a delay in powering the output to the handbrake controller so that the PDM and keypad are powered up first and now it works.
(Hi Nathan, thanks for your answer but the handbrake controller does only provide 5v or 0v so did need a resistor on it)