PDM power connection

[FoxSTI]

hello everyone.
I just want to get an understanding on how the PDM 13 completes the circuit. I read the install manual but it is still not clear. It is very obvious that via a 10 gauge wire? on the M6/1/4" main stud you provide 12V. Now where does the ground connect to?


PS: is 10 gauge pos wire sufficient?

Thanks in advance.

[SprinterTRD]

The PDM mainly switches +12V to the output pins so there are only two 10A ground pins (PDM15 & 30) on the connector for the logic ground and output 9

[adrian]

The wire size is really dependant on how much current you drawing through the PDM. Typically you would select a wire size that is capable of supplying the maximum amount the PDM can draw, in this case 80A. I would select 6 AWG wire so that there is extra capacity to account for transient loads and ambient temperature.

[FoxSTI]

so whatever item it provides 12V to needs to be grounded to the chassis.
in other words, the PDM is not grounded or provides a ground point.

I was thinking i could use it to eliminate the "typical" relay panels seen in race cars.
I don't have one of those, but I do have several relays turning on my fuel pump, C125, Wideband controller, and I am looking to have room to grow and install more items. Fans to be full on via a bypass switch..

[adrian]

As sprinter said the PDM has grounds for any of the switched inputs you use (you should always wire switches or sensors to 0V not ground) and for the special wiper control output (output 9). Everything else should be grounded to the chassis, the PDM simply provides the 12V.

[FoxSTI]

Adrian,

Here is the "problem" I am having.
I am using an innovate motorsports Wideband controller. For accuracy these folks want you to ground it back to the battery and not the chassis. I guess to ensure proper grounding.

I am guessing the PDM can supply 12V to is and I connect the ground to one of the zero volt inputs right?
I love the idea of just grounding to the chassis. I am just not clear if that is the same as grounding directly to the batts neg. terminal and if that is equivalent to zero volts.

I am also wondering if the Motc PDM will essentially replace those race car electrical panels with multiple relays and fuses.

If someone can please chime in that would be appreciated.

[the_bluester]

Rather than to chassis ground, I would ground the wideband controller to the same point as your ECU ground (Assuming you are going to run it to an ECU and not simply a gauge)

Regards the PDM and replacing panels with multiple fuses and relays, that is exactly what the PDM is for, with the added benefit of much smarter control than would be feasible wiht simple relays if you have CAN data gong into it.

This is a rough out of my setup under construction (For as long as Photobucket hotlinking continues to work) The four connectr DT setup on the left has all the outputs and the two on the right all the inputs and ground and the CAN bus

Edit: And photo removed, the great photobucket embedding steamroller has finally got around to me. For anyone who does not know yet, if you have photos in photobucket for purposes of putting them on forums or on web pages with [img] tags, you will now need to pay around $500 AUD a year for it. If you are not on a paid sub now you are toast in the very near future. If you are on a paid sub but not the most expensive one your hotlinking will work until the end of next year so long as you keep paying up, at which time you have to stump up for the highest cost sub to re enable it.

Bye bye photobucket...

[adrian]

Any item you are simply powering can be connected to the chassis earth. So for example any motors/pumps/lights etc. This also includes the wideband controller.

0V pins on a device are a bit different. These are used where the device (in this case a PDM) is measuring a voltage signal. So for example if you had a toggle switch that you want to wire into the PDM you would wire one side of the switch to the input and the other to the 0V.

The reason these are different is because any time there is a lot of current flowing (in the case of the chassis earth points you might have 40-50 amps depending on whats connected) no matter how good your connection is you will get a small voltage drop. Now if you were to wire a sensor to this that voltage drop would cause the measuring device to read the wrong voltage and give you inaccurate sensor readings. So the 0V wires are used only for sensors that are very low current, this reduces the chance of voltage drops and makes the readings more accurate.

In the case of the PDM it isn't as critical as it only has switch inputs but other devices (such as a dash) that are reading actual sensors this becomes important.

As for your lambda device id assume the reason they are saying to wire it back to the battery is because they are concerned about voltage drop to the sensor (the voltage level is reasonably critical when controlling lambda sensors). As long as you have good earth points on the vehicle then it makes very little difference wiring to the chassis. Definitely don't wire it to the 0V on the PDM, you will damage the PDM.

[FoxSTI]

Thank you for the explanation.
What are some uses of the 0v on the PDM?

What does the software on the pdm allow for ?
Does the pmd interface with the logger dash? C125/7? If so to what extent?

The one, only outputs 12v is this right ? (As opposed 3-5v or pwm?)

[adrian]

What are some uses of the 0v on the old?

I'm not sure exactly what you mean. The 0V pins are used as sensor reference grounds.

You can download the PDM software from our website here and have a look at it. There are also a number of webinars here on the numerous functions available and how to set them up.

The PDM has a CAN bus that can transmit all of the input/output statuses/voltages/loads/currents etc plus a number of custom transmit and receive messages. The C125/7 can send/receive CAN messages to/from the PDM. Dash Manager is supplied with templates that read the generic output stream from the PDM.

The outputs are all battery voltage, whatever voltage you supply the PDM is the voltage on the outputs.