'Ignition' Circuit on PDM - How do you do it ??

Hi Guys,

Wonder if you might be able to help/ or point me in the right direction please.

I'm about to start wiring up my E30 Racecar, I have installed a 'Cartek' 16 channel PDM.

I've assigned most of the channels to the car, however, i have assumed one channel will be an 'Ignition' Channel.

This will provide power to the following circuits - similar to Switching a keyed ignition to the 'Run' Position.

ECU

Injectors

Coils

Gauges (Rev Counter, Oil Pressure, Coolant Temp, fuel level)

Brake Lights

Reverse Lights

My issue is that these 6 circuits will of course have their own current draw and therefore should be 'Fused' individually (I assume),

Even if i had the extra channels available on the PDM (which i don't), it would be daft to have a button which would provide the feed for the Brake lights and reverse lights individually, however the only other solution i can see is to add a seperate in line fuse box under the dash somewhere, Which in term defeats the whole object of having a solid state PDM.

How is the issue usually overcome please?

Any help or pointers greatly appreciated please.

If you post what's using other channels you've already assigned, their expected/nominal current draws, and the PDM's current rating for the channels, those more experienced may be able to give a better guide to allocations?

Sure thing, sorry didn't wanna make the first post too long.

So I've got the following:

Each of the 16 Channels can take 15A, to take a load of up to 30A, two channels can be combined.

Ignition (this is the circuit in question)

Fuel Pump1 (15A)

Fuel Pump 2 (11A)

Starter (Relay Feed)

Sidelights (2A)

Dipped Beam (9A)

Indicate Left (5A)

Indicate Right (5A)

Heated Screen (25A) So Requires 2 Sections of PDM)

Wiper Slow (TBC)

Wiper Fast (TBC)

Hazards (10A)

Fan (11A)

Horn (15A)

thanks again

Many PDM models can be setup so that a single switch (ignition) can turn on multiple outputs (circuits), each with different load limits. Or you can use logic to turn off things like fans and lights while the engine is cranking. I can't tell from the Cartek description, but it seems like this is just a switch panel, that allows 16 buttons to control 16 circuits.

Is there any way to setup one button to control more than one circuit?

Hi David,

Yes that makes sense, i wondered how other units worked, i think maybe this is a bit more simple, and as you say 16 buttons control 16 circuits.

I have emailed Cartek to understand how they would recommend running multiple outputs from a single switch...

I'll report back, but i fear the answer may be a small additional fuse box...

The Cartek units are preconfigured out of the box for ease of use/install but are configurable to control multiple circuits with a single button via software. Unfortunately it looks like Cartek is still in the OG mode of keeping their software tight to the chest so you'd probably have to reach out to your dealer to get ahold of it.

Hi David,

Interesting, how do you know this and do you know anyone who might be able to help please - i have been in contact with cartek directly and it seems they say its not possible... although I'm still not 100% sure they understand my question....

Would be great if i could make it control multiple circuits from a single button!

Well...color me an idiot. I apologize I was conflating 'CarTek' with 'Moristech'. My apologies, if you want circuit protection on the different legs of the ignition circuit you'll have to do what you ultimately don't want to do - a downstream fuse box.

Much of it is going to depend on how you prioritise the implimentation of the controlled circuits - for some I would certainly do it differently, with circuit breakers supplimenting the PCM, and probably integrate some column switch-gear. I say "circuit breakers" because there are many brands of resettable "fuses" that don't use a fusable link, and can be reset with the simple press of the button on top - they're available in a wide range of ratings and may be an option, and there are also drop-in solid state relays that replace the old style with solenoids and physical contacts.

You don't seem to mention what ECU you're using - I would expect to use that for controlling many of the devices you list, such as the fuel pumps, cooling fans, ignition, injectors, etc, which would be best served using that - this would then free up the PCM for the things that need actual driver inputs - like horn, lights, wipers, etc.

Hi Guys,

Thanks for the help and advice, @gord do you have any tips or advice on good brands/ styles of fuseable links which can be reset easy? the ones im finding seem to be high load..

Im using an emerald ECU, so again nothing too high tech, although it will control these devices you mention, it works on a switched earth so the items all still need power..

Thanks again

Ah, that does complicate things. obviously we're looking at it from different perspectives and what I would do is differnt from your intent.

This is the type of circuit breaker I mean - there will be different providers, of course, so stick to known brands - https://www.demon-tweeks.com/nz/eta-series-1610-circuit-breaker-242598/ - seems there's an option for manual tripped ones, too, to isolate circuits you need to manually deactivate/isolate. Your local auto-electrical, or electronics, stores may carry them a bit cheaper. DT also list a slightly cheaper 'marine' option, but don't know the brand or why they're cheaper there.

option a/ I'd fabricate a small block (3D print or commercially available) wired for the electronic circuit breakers (see above) supplying individual power to a bank of solid-state relays, the relay's "solenoid" getting 12V from the switch panel and the ECU ground operating them. It isn't what you seem to be looking for, but not sure how you would get that with what you have to work with.

option b/ change the ECU for one that can power the ECU controlled circuit, the advantage is it would pretty much leave the pad free for driver inputs, disadvantage is it will require a rewire and re-map.

option c/ if you have the budget, have you considered a second PDM that's operated through a steering wheel mounted panel for the driver inputs?