Thanks guys - lots of great ideas here. It's good to hear that i'm not in as unique a situation as I feared... Time to play and see what I can let the smoke out of :)
Josh --- In Repeater-Builder@yahoogroups.com, scom...@... wrote: > > > Hi Josh, > > You can mod your Micor, but you'll keep running into similar problems when > you interface your controller with other repeaters. COR outputs can be driven > by Darlington transistors, LED drivers, squelch ICs, etc., and not all will > go as low as you want. > > Here's how we've designed our controllers' COR, CTCSS, and logic inputs for > many years: Feed the COR signal to the top of a voltage divider. The upper > resistor is 10K and the lower is 4.7K. Feed the junction of the divider to > the base of an NPN such as a 2N3904, 2N2222, etc. You'll have a 3:1 voltage > divider that in essence multiplies the transistor's base-emitter drop by > three, so the input threshold will be ~2V instead of ~0.7V. And, you'll have > 10K and an NPN to buffer the outside world from whatever logic IC you're > using for your input port. > > If you want a pullup resistor, tie a 4.7K from the top of the divider to +5V. > > You'll find this circuit in all our schematics at www.scomcontrollers.com. > > 73, > > Bob > > > > Bob Schmid, WA9FBO, Member > S-COM, LLC > PO Box 1546 > LaPorte, CO 80535-1546 > 970-416-6505 phone > 970-419-3222 fax > www.scomcontrollers.com > > > > > -----Original Message----- > From: Josh <josh.kit...@...> > To: Repeater-Builder@yahoogroups.com > Sent: Mon, Jun 21, 2010 9:57 am > Subject: [Repeater-Builder] Micor COS issues.... continuing > > > > > I've been fighting this issue for a while now. I've tried some bandaids to > deal with it, tried multiple repeater controllers (including one I designed > myself with an ATMEGA328 Microcontroller (I'll probably be releasing this > design as open source coming up)... and I'm fighting the same problem > everywhere... My micor COS signal is weird. > > When the squelch is closed, I get right around 8 volts, taken from pin 8 of > the modified mobile audio/squelch board - the tried and true process just > about everybody uses..... When the squelch opens, I'm at not ground > potential, but right about half a volt. This isnt really the sort of logic > signal I want (I want this thing to be dead nuts zero, not half a volt). > > What is the deal here? > > I've tried adding resistors in series to fudge things and cause voltage drop, > but thats not really even working that well. I've tried the 2n2222 circuit, > but that doesnt really have a lot to do with this (although a variation of > that might come into play I suspect) > > How do I best solve this so I can get my repeater on the air?? This is very > close to the last issue I have remaining to solve. > > Help / advice is greatly appreciated. > > Josh >
