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Canbus / Power distribution systems http://www.gt4dc.co.uk/forum/viewtopic.php?f=13&t=6277 |
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Author: | Nibbles [ Mon Feb 04, 2013 5:09 pm ] |
Post subject: | Canbus / Power distribution systems |
I believe that is the term normally used. The concept is an alternative to running every single signal back to a centralised control through a large wiring loom. Instead you place a small interface module near each item or group of items which either produce a signal to monitor (e.g. fuel gauge) or control / drive (e.g. fuel pump, light bulb). The modules then link up via a common small cable, typically 3 or 4 cores, carrying signal and power. This drastically reduces the quantity of cable required and complexity, saving huge installation costs. It's something I have been doing for years in fixed installation round buildings etc, even using radio links for some agricultural applications to save miles of burried cable. From what I can gather, systems currently available for automotive use are highly expensive. If this is the case then it's probably worth me having a further look at producing something more sensible. Probably the main market would be kitcars, maybe motorsports but most with enough money to rewire cars would probably go for proven makes anyway. Any information that anyone can provide on what's available would be helpful, including suppliers, protocols, typical installations etc. |
Author: | johnyboy1976 [ Mon Feb 04, 2013 6:09 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
The Motec PDM 15 im thinking of getting is £1300 - sure don will have some info |
Author: | Nibbles [ Mon Feb 04, 2013 6:13 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Is that £1300 for just 1 module, of for a whole system for a car ? I'm thinking in terms of £50 - £100 per module with maybe 6 inputs & 6 outputs. |
Author: | johnyboy1976 [ Mon Feb 04, 2013 6:18 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
http://www.racedatasystems.co.uk/motec- ... odule.html I was told thats what i would need for mine to get rid of all the under bonnet relays / fuses ect and remove lots of unnecessary wiring |
Author: | Nibbles [ Mon Feb 04, 2013 6:29 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Ouch. Not sure how 1 would reduce wiring, as it would all still need to wire back to the single unit. All it would do is remove the need for fuses. |
Author: | Nibbles [ Mon Feb 04, 2013 6:45 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
One of these (or similar) per output http://uk.rs-online.com/web/p/mosfet-po ... s/0445412/ Plus processor, canbus interface, ancillaries - approx. £10 component cost. Plus PCB Plus box. |
Author: | two_OH_five [ Mon Feb 04, 2013 6:49 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
To reduce wiring you do need two minimum, 1 front and 1 rear Their kit would be completely useless in the kit car scenario. It just replaces the 20 quid fusebox with a grands worth of kit. They have taken the modern concept of distributed control and implemented it in an archaic fashion. Yes it does have some benefit (staged shutdown etc) but it misses the point by a metric mile If you look at a can based car most modules have local controllers. For all it's bells and whistles the bimmer wiring is very svelte That's why I floated the idea ..... |
Author: | johnyboy1976 [ Mon Feb 04, 2013 7:33 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Well if you can make me a system then id rather money go to you |
Author: | two_OH_five [ Mon Feb 11, 2013 7:18 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Blimey, If you want to do it properly so you only have to run a 4 core cable round the car it don't arf add up quick I've missed a few things off too Doors could obviously be simplified but as is allows for fancy tricks like windows up when you lock PDM1 - Front Of Car Out 1 - N/S Flash Out 2 - O/S Flash Out 3 - Side out 4 - Head Out 5 - Main Out 6 - Horn Out 7 - Wash Out 8 - Wipe Out 9 - Driving Lights PDM 2 - Cabin IN 1 - Turn Left IN 2 - Turn Right IN 3 - Hazzard In 4 - Horn IN 5 - Side IN 6 - Head IN 7 - Main IN 8 - Flash - combine with Head signal? IN 9 - Wash - IN 10- Wipe -- best left as is, in dash wiring IN 11- Blower 1 -- best left as is, in dash wiring IN 12- Blower 2 -- best left as is, in dash wiring IN 13- Driving Lights IN 14- Rear Fog IN 15- Brake IN 16- Fuel Pump High IN 17- Defrost OUT 1 - Dash Light -- best left as is, in dash wiring Out 2 - Blower OUT 3 - Left Flasher OUT 4 - Right Flasher OUT 5 - Main Beam OUT 6 - Fuel Level (analog) OUT 7 - Fuel LEvel Warn PDM 3 - Door NS IN 1 - Window Up IN 2 - Window Down IN 3 - Lock IN 4 - Unlock OUT 1 - Window Up OUT 2 - Window Down OUT 3 - Lock OUT 4 - Unlock OUT 5 - Mirror Left OUT 6 - Mirror Right OUT 7 - Mirror Up OUT 8 - Mirror Down OUT 10- Mirror Heat PDM 4 - Door OS IN 1 - OS Window Up IN 2 - OS Window Down IN 3 - NS Window Up IN 4 - NS Window Down IN 5 - Lock IN 6 - Unlock IN 7 - Mirror Select IN 8 - Mirror Up IN 9 - Mirror Down IN 10 - Mirror Left IN 11 - Mirror Right OUT 1 - Window Up OUT 2 - Window Down OUT 3 - Lock OUT 4 - Unlock OUT 5 - Mirror Left OUT 6 - Mirror Right OUT 7 - Mirror Up OUT 8 - Mirror Down OUT 10- Mirror Heat PDM 5 - Rear IN 1 - Boot Open IN 2 - Fuel Level (analog) IN 3 - Fuel Warn OUT 1 - Tail OUT 2 - Brake OUT 4 - N/S Flash OUT 5 - O/S Flash OUT 6 - Brake OUT 7 - Fog OUT 8 - Fuel Pump?? |
Author: | Nibbles [ Mon Feb 11, 2013 7:40 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
I like it when people do my homework for me Add in rear wash & wipe to 3 of the modules. Plus rear heat. It's a good starting point though, I'll start adding to it when I start looking at it a bit more seriously. I would be inclined to keep the heater module as standard as there's quite a complexity of actuators, fan speeds etc. Just use a single output so it can be switched off under software control when starting. |
Author: | two_OH_five [ Mon Feb 11, 2013 8:51 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Need to work of out for the model I think I can see why some things are state change and some are polled - there's potential for boatloads of traffic if everything runs polled |
Author: | Nibbles [ Mon Feb 11, 2013 10:04 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Looking at what I/O is available on the 40 pin dsPIC, I'm looking at: 8 output drives (20A I think) with current sensing for fault report (short or open circuit). 5 analogue inputs 0-5V (or maybe 4 plus power supply sensing) 6 digital inputs. All inputs will probably have the option to link a pull up resistor to sense contacts / resistive sensors. Alternatively, maybe double that (minus 2 digital inputs each for internal I2C) to allow double canbus for redundancy. As regards polled / state change messages, I'm in favour of constant polling in the background to correct errors plus state change messages which take priority in order to keep the system responsive. I'm never in favour of just using state change messages and relying on data at the far end not getting accidentally changed by hardware or software glitch. Such methods are favoured by PC programmers and lead to frequent power off / reboot or right click & refresh. |
Author: | Nibbles [ Mon Feb 11, 2013 10:06 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Looking at progressing this a bit quicker so I can get a prototype run of this plus all the board options for the digidash all in one hit. |
Author: | two_OH_five [ Mon Feb 11, 2013 10:19 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
Trouble is you can't do responsive across an io matrix like that using pure polling so state change is a requirement What you need to know is in a realistic test setup what polling can you get without flooding the bus Can is also carp - you can't do a direct register rtread as far as I recall. You have to request that the device broadcasts its state and then wait for it to get back to you. Or everything dumps status every so often and a background routine sniffs relevant data Hence I've built a system model to try a few ideas out |
Author: | two_OH_five [ Mon Feb 11, 2013 10:23 pm ] |
Post subject: | Re: Canbus / Power distribution systems |
From a hardware perspective what I have modelled is each pdm has a bus master and a bus slave All PDM inputs are connected to the bus master and all outputs are driven by the bus slave. I'll try knock up a quick drawing if you want |
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