CDM 1250 accessory pinout question

[NIFOG291]

I was playing around with the CDM software and discovered the selectable digital and analog pins for my CDMs. Can anyone tell me the voltage out on a digital pin? I want to try to use a micro-controller like an arduino or basic stamp to control functions like turning on house lights or opening garage door with a key of the mic. Also, is it possible to do something like APRS through these pins? Maybe the reverse, could I send an alert tone if someone unauthorized got into the station? Its all just theoretical right now. I just want to tinker with it.

thanks
Joe

[kb4mdz]

I don't have any reference material here, but the voltage can't be any higher than the radio's supply voltage, and it can't be lower than 0 VDC. I'll dig it up & post it here.

Some of the digital pins have different current source/sink capabilities, too. I'll mention that.

And just one description of what you can do:

http://www.rayvaughan.com/recall.htm

[arnu]

The CDM I/O pins are open collector NPN outputs with 4.7kOhm pull-up resistors to +5V
Pin 4 (GPIO2) has a pull up resistor to +12V (this output is designed to drive a relay connected to +12V) Don't forget the diode !
Programmed as inputs simply pull them to ground. (Programmed active low)
Try to avoid to feed +5V or even +12V into any of these pins - since it will fry the transistors if the output is switched low.

I am happy to help if you have any questions.

Alfred.

[jcw1979]

alfred can you elaborate on the diode for pin 4? im trying to use pin 4 to trip a 12 volt relay but when i attatch ground to the other side of the relay my 12 volts on pin 4 disappears!

[arnu]

The CDM outputs switch to ground. They usually have only resistors to pull up to 5 or 12 volts.
So in order to trigger the relay - connect it between pin 4 and +12V (switched B+ pin 13 works best for that)
Make sure the relay does not draw more then about 100 mA = min 120 Ohm coil.

The diode (any general purpose diode like a 1N4004 ... 4007 or a 1N4148 will work) is parallel to the relay coil.
It is reverse polarized - meaning - the side with line on the diode is connected to +12V.
The diode is only necessary when you use a relay since turning a coil Off will produce a nasty power spike which will most likely fry the CDMs output transistor after a few times. The diode will simply short the spike.

|----|<----| <= diode
B+ Pin13 ----*---[ / ] ---*---- Pin 4 <= relay

Hope my little line art schematic helps.

Alfred