Help with open collector transistor

Hi,   I have a receiver unit for a wireless PIR.

It has 4 logic open collector transistor outputs. How would I connect this to the netduino inputs.

The receiver uses a 12v supply

Any help would be appreciated.

I have attached the wiring diagram from the reciever

Thanks

I think this would work, the signal would be inverted but that shouldn't really matter since you only need to interpret the signal opposite of how you normally would:

 circuit.jpg   15.09KB   14 downloads

When the PIR output is a logic high, your Netduino will see a logic low and vice versa. The resistor connected to 5V is the same pullup as seen in the left picture of the image you attached.

EDIT: Simplified the circuit. Oh, and have the Netduino input pin configured in pulldown mode.

hm, for my pirs is just use netduinos on-ic pullups.

@hanzibal what? on your diagram is a pullup, wich is ok, but you dont want "and have the Netduino input pin configured in pulldown mode."

that doesent even make sense. (it may waste energy and maybe burn something!) -

btw: normal netduino doesent have pulldown mode, only pullup

only gen2 hgave pulldown's.

another hint: when using internal pullups dont make a external want. and vice versa.

You are right, internal pull-down should not be there, my bad. It won't burn though since current will be limited by the 2k resistor.

Btw NooM, do you know what value the internal pull-up/down resistors are?

no sry i dont know, it should be in the uC's datasheet

i guess its around 50kohm