Currently looking at the PDM25+ for use in a road car (classic with engine transplant).
Obviously it has many great features and getting rid of all the relays and fuses is a big plus, but how do you control or use anything that doesn't require the ignition to be on? (I believe the MOT doesn't require the horn to work with the ignition off but most cars seem to anyway).
I guess items like alarms and remote keyless entry will have to be its own system and fused? Thought it would be good to connect the door locks into the PDM and potentially use a CAN message from an alarm (or other device?!?) to unlock and "enable" the car? Does the Ignition feed completely kill the power or does it just sleep? Could the USB be always in to keep the processor on but limited function (like a sleep/ wake state) ? Can anything be controlled with just the usb? assuming its solely for setup / config. I ask really as part of the integration would be to have the PDM control the indicators/lights/ fans / electric water pumps etc. so using any of this after the car is "off" would require the PDM to be on all the time or at least for a set time after ignition is off.
i.e. key out, ignition off, electric pump on and fan on until the engine cools to a suitable level. or Lock car and indicators flash. Just nice features like that but is seems either PDM on all the time, or bypass circuits/timers and fuses to allow this kind of thing (and defeat the purpose of the PDM)? Ending up with a PDM power timer? 😣
Thoughts? 😁
Ed.
I have been thinking about this problem too. Perhaps the always on battery drain issue could be addressed with a small solar panel?
Also car is completely gutted so it will be completely new / fresh wiring.
Car is a classic mini being fitted with a 1.8t20v for reference. 😅
The only real place to integrate a keypad wouldn't really fit (would have to start modifying and recovering dash panels), space is about 50mm height and these pads are 70mm? Not impossible but maybe ill investigate the options first and maybe i wont need as many button as i think i will. Resistors and pulldown was my first option (or maybe a DAC?), mainly for the stalks as that will be most of my controls. But I've seen boards that could possibly handle / convert to CAN, like the ECU masters CAN Switch board v3, just weather that can be handled with the PDM. Another job is the dash, I'm looking at a display powered with a PI, so that will also talk CAN and give some IO control. Lots to still consider. 😵
You'd be surprised how well you can integrate the can keypad into a classic car, my PDM and keyboard are in a triumph stag. Admittedly is not a standard car but the keypad, once it's fitted recessed into the transmission tunnel surround ,doesn't look out of place. My lights are controlled by the Key pad while the main beam, wipers and indicators are all off of the ordinal stalks. But they just send a varying voltage to an input on the PDM. That just by using some resisters and the pulldown.
There's various ways around the issues you have with trying to power stuff without the ecu being on. At the moment mine will only require permanent power going to the central locking ecu.
Like George is mentioned I just have a couple of diodes to stop any backfeed going to the indicators. But soon as my battery isolator is switched on the ecu he switched on, ignition is by a kill switch on the dash. there's no key as I will be using the Pass Key for that.
The best way though is by ripping out all the old wiring from your car and start from fresh. As it is a nightmare to try and marry up a new system integrated to an old system. I started to do that but then I realised it was taking too much time and I pretty much ripped everything out and started again. And if your car is anything like mine was then all the wiring most well past its sell by date anyway. My PDM took 160 metres of wire to install.
Thanks for the info, sounds like always on is the better method for me at the moment then. It wont be a daily car and probably need to live on a charger when not in regular use anyway. 🔌 Then some conditions added to maintain an "off" state and an input just for ignition reading i suppose.
Now to work out how best to handle all the controls and switch inputs. Not sure the CAN keypads suit the classic theme.
Hi Ed, There are a couple of ways that you can go about this which each have their own drawbacks.
Firstly, you can leave the PDM switched on all the time so that it can service your outputs as required. The downside is that the PDM will draw approximately 150mA of power which will slowly drain your battery if left for extended periods.
Another option as you mentioned is to have some circuits external to the PDM using fuses, so that they can work all the time when the PDM is powered off. As you say, the downside is that it somewhat defeats the purpose of the PDM.
Another option which we have used with success, is to have a 12V feed to your indicators, horn and dipped light switches. The output of these switches can go to the inputs of the PDM as usual, but the output of these switches can also go to the ignition input of the PDM via a diode. This will mean that when any of the switches are pressed, the PDM will turn on and begin to operate. The downside to this method is that you would need to wire a diode into your loom. Also the PDM has a wake up time of approximately 1.5 seconds.