I wish to interface the output of one Device(A) with another Device(B) that requires a metallic contact closure to start Device B. Device A has two outputs:
1. open collector
2. common held at 0v
The supply voltage is of device A is +5v and 0v
I do not know anymore technical info about device A
Device A is operational when a push button code is input by keypad. At this point the open collector should change state. Can anyone suggest a test procedure to determine whether the open collector is working properly.
Once I know Device A is working I need to feed this output into an interface circuit input that will cause a relay to operate and provide a contact closure to turn on Device B.
I have put together an interface circuit using an NPN transistor (BC547C), a relay - Maplins 2A DPDT 5vdc (coil resistance 125 ohms/operate current 40mA), a diode (IN4007S) and a base input resistance of 6 Kohms.
The transistor collector is connected to one side of the coil and +5v to the other side of the coil. The emitter is connected to 0v and the diode is connected across the coil to protect the transistor against switch off transient voltages.
I have connected the base via the 6Kohm resister to the open collector output. I have connected the common to my 0v of the interface circuit. However, Device A's open collector output does not operate the relay in the interface circuit when I key in the correct code into Device A.
I have tested the interface circuitry in stand alone mode and when a resistive (6kohms) +5v is applied to the transistor (BC547C) base the relay operates with the contacts closing accordingly.
So, I would be grateful for any advice regarding testing the Device A's open collector circuit to prove it works. I would also appreciate any suggested adjustments that may be needed to my interface circuit to enable it to work with this open collector output.
Terence Sutton (tigerterry)
1. open collector
2. common held at 0v
The supply voltage is of device A is +5v and 0v
I do not know anymore technical info about device A
Device A is operational when a push button code is input by keypad. At this point the open collector should change state. Can anyone suggest a test procedure to determine whether the open collector is working properly.
Once I know Device A is working I need to feed this output into an interface circuit input that will cause a relay to operate and provide a contact closure to turn on Device B.
I have put together an interface circuit using an NPN transistor (BC547C), a relay - Maplins 2A DPDT 5vdc (coil resistance 125 ohms/operate current 40mA), a diode (IN4007S) and a base input resistance of 6 Kohms.
The transistor collector is connected to one side of the coil and +5v to the other side of the coil. The emitter is connected to 0v and the diode is connected across the coil to protect the transistor against switch off transient voltages.
I have connected the base via the 6Kohm resister to the open collector output. I have connected the common to my 0v of the interface circuit. However, Device A's open collector output does not operate the relay in the interface circuit when I key in the correct code into Device A.
I have tested the interface circuitry in stand alone mode and when a resistive (6kohms) +5v is applied to the transistor (BC547C) base the relay operates with the contacts closing accordingly.
So, I would be grateful for any advice regarding testing the Device A's open collector circuit to prove it works. I would also appreciate any suggested adjustments that may be needed to my interface circuit to enable it to work with this open collector output.
Terence Sutton (tigerterry)