For any add-on boards such as VR conditioners, optos and OEM interface boards
User avatar
By EdMcGuirk
#55274
I admit I am fascinated by the possibilities of a current sensing PDM. But I also wonder if a much cheaper idea could be almost as useful.

1 - Are fuses and relays really all that bulky and unreliable? How about a CAN bus controlled fuse/relay power center? If the control circuitry can control a set of relays and detect/report fuse and relay status, is that good enough?

2 - What about a smaller PDM that is meant to control power in a local area of the vehicle? Like a small PDM to control all the motors in a door (window, mirror, door lock, etc) or control all the tail lights with just a power wire and can bus wire? Unless a really small generic single port PDM could be a CAN interface to a single bulb along a CAN bus string? OK, that's not a PDM but how much should your power distribution in a vehicle look like a tree fanning out from a center or a bus with a single line that passes by each point?

3 - Might even make the communication protocol modular so that the PDM could be CAN, bluetooth, wifi, serial, etc.

Anybody have an opinion on that?
By dazq
#55288
EdMcGuirk wrote: Fri Feb 11, 2022 4:25 am I admit I am fascinated by the possibilities of a current sensing PDM. But I also wonder if a much cheaper idea could be almost as useful.

1 - Are fuses and relays really all that bulky and unreliable? How about a CAN bus controlled fuse/relay power center? If the control circuitry can control a set of relays and detect/report fuse and relay status, is that good enough?

2 - What about a smaller PDM that is meant to control power in a local area of the vehicle? Like a small PDM to control all the motors in a door (window, mirror, door lock, etc) or control all the tail lights with just a power wire and can bus wire? Unless a really small generic single port PDM could be a CAN interface to a single bulb along a CAN bus string? OK, that's not a PDM but how much should your power distribution in a vehicle look like a tree fanning out from a center or a bus with a single line that passes by each point?

3 - Might even make the communication protocol modular so that the PDM could be CAN, bluetooth, wifi, serial, etc.

Anybody have an opinion on that?
1. This is exactly what my prototype modules have , but with the addition of a current sense (acs type) reporting consumption.
I have some very nice proper OEM style drivers to use later along with fet drives.this is particularly important for some outputs I plan to pwm

2. I have 5 mini modules, front ,rear ,cabin /dash and both doors .
The front controls lights,leveling,fan etc. Basically all bonnet end stuff .
The rear module has both light clusters, tow electric and a few aux circuits.
The cabin controls HVAC, wipers, interior lighting
Doors , all switches and drivers

In addition I have a central gateway input module that takes all the switch gear inputs to transmit to bus. It also deals with obd port .

3. I am using data format from BMW 3series/mini.
The fuel pump and main fans are already canbus sourced from mini and Audi .

For wiring I will have a twisted pair in a ring from the gateway running around the car. Alongside this will be a 3core carrying power and an ignition active line.
The ignition active is for activation of the modules until I learn better how to make it all sleep for lower power consumption .

This is all WIP but I am getting there , my code is based around s development of gpio but for pdu use
User avatar
By EdMcGuirk
#57264
dazq wrote: Fri Feb 11, 2022 7:15 pm Alongside this will be a 3core carrying power and an ignition active line.
The ignition active is for activation of the modules until I learn better how to make it all sleep for lower power consumption .
I did not understand why sleep is necessary but also I should not comment on what I do not know. However I have been thinking more lately and I envision a central PDM with a hard wired ground start from the ignition switch. Then the central PDM would supply power to the CAN bus controller (wherever that is) and all the local PDMs distributed around the car. That way there is no parasitic leakage current when the car is 'off'. I assume all the other CAN bus processors can boot quickly enough to be unremarkable.

Maybe I have blind spots because I envision PDMs as dumb power supplies that just switch power and sense / report status to smart devices elsewhere (Controllers make decisions, Collectors read sensors or buttons and send data to Controllers). I would imagine a PDM to only accept a few commands for each output channel:

Report status to CAN bus,
12V/on,
Ground (optional to allow H bridge configuration),
High impedance/off,
PWM duty and frequency,
High current warning,
Low current warning,
High current disconnect.

Startup
Central PDM needs default output for initial start (like power to CAN bus controller which will direct subsequent actions or just remember previous settings at shut down)
Shutdown
Central PDM turns on from ignition switch but reports ignition switch shutdown to CAN controller and waits for instructions.

What is the value of sleeping processors? Older electronics needed constant power to remember status, is that still necessary? Safety related? Anything beyond brake lights and horn? At worst case only the central PDM could be set up to sleep and wake peripherals as necessary. Or perhaps a small processor at the ignition switch that could sense external interrupts to kick start the central PDM. Clearly I am thinking about lots of independent generic processors instead of combined multi-function processors. Local PDMs could be Arduino ProMini with 8 lower current ports or 4 motors, central PDM could be Mega or Pro Mega with 16 higher current ports, CAN controller could be GPIO, etc. (or other microprocessors as available)

Not trying to criticize, I am curious of reasoning. (response kind of blew up from my original question of 'Why sleep?')
By dazq
#57272
EdMcGuirk wrote: Fri Jun 03, 2022 5:41 am
dazq wrote: Fri Feb 11, 2022 7:15 pm Alongside this will be a 3core carrying power and an ignition active line.
The ignition active is for activation of the modules until I learn better how to make it all sleep for lower power consumption .
I did not understand why sleep is necessary but also I should not comment on what I do not know. However I have been thinking more lately and I envision a central PDM with a hard wired ground start from the ignition switch. Then the central PDM would supply power to the CAN bus controller (wherever that is) and all the local PDMs distributed around the car. That way there is no parasitic leakage current when the car is 'off'. I assume all the other CAN bus processors can boot quickly enough to be unremarkable.

Maybe I have blind spots because I envision PDMs as dumb power supplies that just switch power and sense / report status to smart devices elsewhere (Controllers make decisions, Collectors read sensors or buttons and send data to Controllers). I would imagine a PDM to only accept a few commands for each output channel:

Report status to CAN bus,
12V/on,
Ground (optional to allow H bridge configuration),
High impedance/off,
PWM duty and frequency,
High current warning,
Low current warning,
High current disconnect.

Startup
Central PDM needs default output for initial start (like power to CAN bus controller which will direct subsequent actions or just remember previous settings at shut down)
Shutdown
Central PDM turns on from ignition switch but reports ignition switch shutdown to CAN controller and waits for instructions.

What is the value of sleeping processors? Older electronics needed constant power to remember status, is that still necessary? Safety related? Anything beyond brake lights and horn? At worst case only the central PDM could be set up to sleep and wake peripherals as necessary. Or perhaps a small processor at the ignition switch that could sense external interrupts to kick start the central PDM. Clearly I am thinking about lots of independent generic processors instead of combined multi-function processors. Local PDMs could be Arduino ProMini with 8 lower current ports or 4 motors, central PDM could be Mega or Pro Mega with 16 higher current ports, CAN controller could be GPIO, etc. (or other microprocessors as available)

Not trying to criticize, I am curious of reasoning. (response kind of blew up from my original question of 'Why sleep?')
Although the can operation follows your train of thought it is far more integrated into the system than you consider. It is not "a can controller" but an interface that each module regardless of its function has of its own (unless a hardwired device sharing it's hard wiring with another"smart" module).

Regarding wake up, in OEM the modules put the MCU to sleep and wake when the can interface detects correct traffic( a wake up pattern if you like). This wakes the MCU itself .
NV storage on each module keeps its on state or last known states for when they come back on.

A pdm can just be a single module that takes hardwired and can inputs , then according to its config switches either hardwired outputs or simply sends out a message on the canbus (just in case anyone is listening).
This makes it just a smarter fuse box but still offers features a normal fuse box may not offer eg to trigger wipers for 5 sweeps after wash has been activated for more than 2 seconds, that sort of thing.

It is amazing how little current consumption can quickly drain a vehicle stood for a few days......
User avatar
By EdMcGuirk
#57280
Yes, I assume that OEM systems have complex interactions but speeduino adjacent CAN bus systems could be simpler. OEM systems are heavily interactive and specialized to save pennies by the thousands and aftermarket PDMs are smarter than needed because they are so expensive they need to do more in one box (difficult to sell multiple expensive boxes if one expensive box does not 'do it all')

I know that the CAN bus does not have a single master controller but I think that simple generic CAN modules would tend towards accepting commands from one or a small number of controllers. If I think of converting my non-CAN bus car to one with a CAN bus, I am largely looking at dumb power distribution, dumb button box interfaces, sensor interfaces, dashboard display, and one controller (or a small few) acting as a hub. For example as opposed to a button interface sending a command directly to a PDM to execute a complex task based on a sensor value with result displayed on the dash.

I understand integrating into an existing CAN bus could likely be completely different. Could one style do both? Or do they need to be completely different?
By dazq
#57285
I think what you are considering is very similar to my mini modules, simpler modules with more specific tasks rather than a do it all option list.

Could one style do both? Or do they need to be completely different?

Integrating into an existing OEM setup is very different and potentially much more complex than starting from scratch with a non canbus vehicle ( as mine is too). I would say that most if not all the aftermarket pdu I have seen are designed for self created networks or using existing networks but converted to the aftermarket data packet format .
User avatar
By BenBrinkley
#58840
Have you looked at the micropdm? It's basically a can controller that controlls circuts up to 2.5 amps which is enough for lights or a relay for heavier loads. Each unit has 7 outputs and you can have up to 4 units for 28 outputs

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