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...@gmail.com> 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
